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Scott PAB Engine Strip-Down

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Scott PAB Engine Strip-Down

Post by nutgone on Wed Dec 12 2012, 23:09

Right, I've been tinkering with this engine so much since I bought it I thought I would start a thread here about my work on it (the "Pride & Joy" section just doesn't seem like the right place). So consider this an extension to Abes' original "Scott PAB Restoration" thread (where I will be looking into from time to time for reference points).

So far I've had the head, barrel & piston off to de-coke the ports, but I didn't get many pics of that, then I've repaired the fuel tank gauge & touched up the paint (where I got petrol on it). But recently, when I've slowed the running speed down a bit, I've been noticing a little bit of mechanical noise from the timing case. I originally thought this was perhaps the governor, but now I think it is the timing chain (or perhaps a bit of both). Either way, it's not a massive noise, & for all I know it might be completely normal, but I want to do this, so I will.

As usual there's a Photobucket album especially for this project (& I'm calling it a project, because Abes has already done the restoration), the album can be found here....

http://photobucket.com/nutgonesscott

So I will start with a few shots of when I did the head, barrel & piston. Here's a shot down the barrel, as I was putting it all back together....



& here's a couple of shots to show you the drastically domed top of the piston....





The fuel gauge bit can be seen in my other thread, I don't think it's worth going over that again here.

Today, however, I decided to get to the bottom of the mechanical noise & take a closer look at the governor to see if there was any way I could slow it down a bit. I started at the governor output end, but quickly drew a blank, realising I would have to take the timing case apart.

There's a lot of nuts holding it in place, & I wasn't sure how tight all the bearings were going to be in there, but after loosening all the nuts & removing one of the bearing end plates I managed to get it to slide off without too much trouble....



Revealing the well made innards of the Scott timing area. With a lovely little duplex roller chain....



& here's the crank shaft end nut, I couldn't work out why it looked so intricate though....





But when I later managed to crack the nut I realised what it was all about. I had carefully bought the engine to TDC & marked it in several places, including the chain, twice, & the crank shaft & magneto sprockets. But it was only once I cracked this nut I realised it was captive! The nut acts as it's own puller for the crank shaft sprocket which is on an un-keyed taper!



So that's my careful marking & the engine's timing up the creak! Rolling Eyes affraid
Actually, I marked the magneto drive plate on the outside as well, so all is not lost. At least I won't be starting completely from scratch.

Anyway, next I took on the governor. I managed to get it out of the timing case, I did mean to take some pictures before I took it apart, but sadly this didn't happen, so here it is in exploded form....



I will continue this later....

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Re: Scott PAB Engine Strip-Down

Post by stationary stu on Thu Dec 13 2012, 10:44

Nuts I bet your parents are glad your not a surgeon, one coff and you'd have them on the kitchen table sharpening up a knife and wondering if you can get your dremmel into the pipes that go to the lungs.
lol! lol! lol! lol! lol!

Stu.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Thu Dec 13 2012, 10:56

stationary stu wrote:Nuts I bet your parents are glad your not a surgeon, one coff and you'd have them on the kitchen table sharpening up a knife and wondering if you can get your dremmel into the pipes that go to the lungs.
lol! lol! lol! lol! lol!

Stu.

The silly thing is she now starts like a dream, the last 3 or 4 times I've started her she's fired up first pull. But it turns out I may have been right about the noise, it looks like the chain's quite slack. I've taken the tensioner apart in the hope it was sticking, but there's a hefty spring behind it, so it could be the chain itself, in which case it'll have to stay like it!

Anyway, I'll carry on the thread in a little while, there are some other bits I've found.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Thu Dec 13 2012, 12:11

Right, so I've got the chain case off, found out the chain is a little slack & probably making the noise, or most of it, I've also found it really wants a good rinse out in there, which is pretty much standard when you take something like this apart, but all in all it looks pretty good in there.

One thing I did find, where the throttle control rod passes through the timing chain case it passes through a tube. I took the arms off each end & found proper little ball journal bearings in there! Couldn't believe it! I've since popped them out, but here's a quick pic....



It actually would've made more sense to just use plain bronze bushes in there, as ball & roller bearings are designed to rotate, not just reciprocate back & forth, never making a complete revolution.

After I took the governor out I had a look inside the timing case. It looks like it has been making contact with the case recently(ish)....



I drew back a bit, to show you where we are....



So that will require some investigation, as I'm not quite sure what could be causing that. There also seems to be some rubbing on the governor weight arms, inside the main body of the governor, but I forgot to get a picture of that & I'm not too sure if or how it could be occurring, it may even just be machining marks, but it doesn't look like it.

The bearings inside the governor seem fine, all except for one, the smallest one but also the least important one. I'm going to see what I can do with it & get some better pics of it today, it appears to be pressed into the piece which the weight arms act on, on the end of the shaft which acts on the throttle linkage parts. I'll try & get some pics & maybe it'll make more sense then.

I've also now got the starter dog teeth out. These were worn & giving me trouble, which is why I've been starting it with a strap (which I prefer). Anyway, here they are....

Here's the crank shaft nut part....



& here's the actual starter dog shaft part....



I'm not sure weather to just have a go myself with the Dremmel &/or a file, or leave it for a later date? I have kind of decided I'm going to have a go at removing the flywheel today, & if it comes off easy I might as well split the crank cases & clean it all out in there & check the bearings. I was going to leave it for next winter, but now I've gone this far I might as well finish the job off. It all depends on how easy the flywheel comes off, but ever since I took the top end apart I've been wanting to get into the crank cases & clean it all out, I'm a bit worried about the oil feed holes for the main bearings, they are fed by troughs just under the base of the barrel & there was a lot of carbon deposits in there when I had the barrel off, so I would like to have it all apart for cleaning, but it's not the end of the world if I can't.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Thu Dec 13 2012, 12:32

Well, I guess that answers that question....



I only went out for a fag, thought I'd have a quick go at it, found a socket that fits, extension & long bar & off she came. It's another captive nut/self extracting taper affair, so I had to crack it twice. This end is keyed though, as the flywheel has timing marks on it.

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Re: Scott PAB Engine Strip-Down

Post by kevjhnsn on Thu Dec 13 2012, 13:16

well your cracking on ,well off lol with it now mate
looking promissing sofar mate
kev


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Re: Scott PAB Engine Strip-Down

Post by nutgone on Thu Dec 13 2012, 19:40

kevjhnsn wrote:well your cracking on ,well off lol with it now mate
looking promissing sofar mate
kev


Wait til you see what I've done today/tonight! It's been coming apart really well. I need to start taking a few more pics though, but when you get on a roll like that it's easily forgotten.

& I haven't finished yet, just come in for an after-dinner coffee & quick sit down. Off back out there now.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Thu Dec 13 2012, 23:36

Right, well, blimey, where do I start.... scratch scratch scratch

Today I carried on, as you can see above I got the flywheel off, easier than I expected, but I suppose it helps that Abes only took it off a few months ago. It's another captive nut affair, but this time it's a keyed taper.

I followed by taking off the trumpet shaped bit of cowling from behind the flywheel, this usually funnels the spent air into the flywheel vanes for cooling, once it came off I found a hole with a wick in it....



Then I took the front bearing cover plate off (which has a strange trough in it scratch ) to reveal the outer bearing (fed by the above mentioned wick)....



Here is 2 bearings (flywheel end), the other end just has one. Both ends are only sealed by plain bronze bushes, I was expecting something a little more technical, so it was a bit of a let down.

Anyway, on this flywheel end we have the inner bearing, then the plain bronze sealing bush, then we have an empty chamber before the outer bearing. Now this chamber is supposed to be fed with oil from the crank case, hence the wick, which dips into this oil & feeds it to the outer bearing. Any excess oil gets on the outside of an oil flicker, cast onto the back of the flywheel centre, which has a spiral oil-way cut into it, so it feeds this oil back towards the engine & into a trough which then empties, via a small oil-way, into a small copper pipe union underneath & just drips onto the floor (there shouldn't be that much of it).

But, going back to the chamber between the bearings, this has, over the years, been packed with grease, which although seems the right thing to do when you haven't taken the whole thing apart & analysed it like I have, but this has eventually made the outer bearing go a bit dry. Fortunately it's in fine shape, I've given it a clean & am still in the process of getting all the grease out of the chamber. I also need to find some of this wick material, it closely resembles pipe cleaner, as it has a wire centre. I've also found some of the same material on the Briggs & Stratton RC, it feeds the contact breaker cam on that engine, but it could do with replacing on there too. Does anyone know where to get it??? Or is it just a pipe cleaner??? (maybe a lighter wick??? Some of those have wire centre, don't they???)

Right, so what else. Well, I took the piston off, as I didn't want it getting damaged. I've taken a few pics of it, as my last ones were rubbish. Here it is, with it's drastic dome....





As you can see, it has 3 rings, normally 2 strokes just have 2, but this is a good thing, as the 2nd ring is broken. In this next pic you will see that it's only a small piece broken off, & it's firmly wedged in next to the peg, so I'm just going to leave it, the compression's fine & I think the smoky running is more due to the 25:1 2 stroke mixture I'm using. I also took these next pictures to show the heat scoring on the piston skirt, I think these pics make it look worse than it is, & I think it was mostly due to the badly coked-up ports. Anyway, here's the pics....





You'll also notice in those pics that the top ring has a steel sleeve around it, I've never seen this before, if anyone knows what it's all about then by all means chime in & let me know. I'm guessing it's got something to do with controlling heat expansion & stopping the top ring either widening the ring groove or stopping it melting into the aluminium piston, as top rings can do on hot engines (especially 2 strokes). Here's a slightly better pic of this for you....



I also took some pics of the rather impressive porting in the barrel....







& I'm guessing this exhaust porting makes it a twin port???



A close-up shows you I've still got some work to do as regards de-coking of these ports, but it's not an easy job, any little tricks of the trade here would be very much appreciated....



So, the crank shaft is out & the cases are empty, I even managed to get the magneto drive shaft out. The crank webs are of an interesting construction, the big end spindle is held in by pinch bolts, I'll have to get a picture of that tomorrow.
Funnily enough it was the crank webs which looked worst off, they were quite badly coked-up, which seems strange to me, I wonder if it was due to the badly coked-up exhaust ports that this engine seemed to be "blowing back", as the crank case, the crank webs & the transfer ports were also quite badly coked-up. Well it's either that or there's a fault with the design & it doesn't breathe properly.

Also, as a quick footnote to tonight's input, the oil-way holes I was so concerned about, at the base of the cylinder block, cast into the crank case; well I've been poking bits of wire down them & trying to work out where they go. I found 2 brass blanking screws in the crank cases, one on each side. When I removed these I found out where these oil holes go to. It seems they pass behind the plain bronze seals & don't do anything at all. They must have been put in there for a previous design idea, maybe the seals or bearings were different on the original design, whatever the case, there was obviously a change of heart at some point & the plain bronze bushes were put in & these oil-ways were blanked off to avoid any loss of crank case pressure.

I'll have to get some pics of that tomorrow as well Rolling Eyes Embarassed

So all that's left is to clean everything up & start to put it back together, hopefully resolving the few problems I've found along the way, namely the timing chain tension & find out why the governor has been making contact with the timing case. I've also found marks where the chain was making contact with the timing case, fortunately it's very minor, so probably a good thing I decided to do this job now instead of next winter.

I'll leave you with some pics of that....





Night night.

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Re: Scott PAB Engine Strip-Down

Post by stationary stu on Fri Dec 14 2012, 10:41

There's a couple of things I picked up on, not seeing everything is difficult to make a solid definition of the problem but where the marks are that it's catching the case can be 2 things, is there spacer is missing or the bearing is worn allowing movement. Also "the wick" is that not some kind of oil seal?
Your getting on well so keep up the good work,

Stu.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Fri Dec 14 2012, 12:24

stationary stu wrote:There's a couple of things I picked up on, not seeing everything is difficult to make a solid definition of the problem but where the marks are that it's catching the case can be 2 things, is there spacer is missing or the bearing is worn allowing movement. Also "the wick" is that not some kind of oil seal?
Your getting on well so keep up the good work,

Stu.

The wick is definitely a wick Stu, & it feels very much like a pipe cleaner as it's got a metal wire centre. I've seen it on other engines as well, but it's easily missed as they are usually put in awkward places & they get squashed in so you can't spot them.

I think I will try some pipe cleaner, see how it does. (I see an experiment coming on study )

Not sure about where the governor has been rubbing. This engine has been apart before, as there was a nut & bolt missing at the bottom of the crank case (it was still sealing though, & by the looks it had been missing some time) & there's a small woodruff key missing from the magneto drive shaft. There are other signs that it's been apart & things have been done or left out, but it's all minor stuff. I'm wondering if there should be a shim in there or something.

I'll try & get better pics of all this stuff today. Suppose I'd better get on with it, glad it's only just outside the back door, is p155ing it down out there!

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Fri Dec 14 2012, 15:14

Right, I thought I would do a quick lunchtime write-up to avoid getting too long winded this evening.

I've taken some better pics of the oil/lubrication system. So starting with those oil troughs I was so worried about at the beginning (basically the main reason for taking the crank cases apart), here are the bits I mean, they are on the tops of the crank case halves, just below where the barrel goes on, one on each side with a little hole (which I thought fed a bearing)....





Well, these don't actually do anything. Eventually I found out where they go to. One comes out on the bottom of the crank case here....



It is normally blanked off, like so....



The other one comes out here....



& is normally blanked off with a plug, but also notice the copper pipe in this pic, I'll get to that right now....



Now, that copper pipe is linked to an oil-way in the crank case....



This oil-way joins up with a similar hole on the front bearing cover plate....



The front of this bearing plate looks like this....



As you can see, it also has a trough in it, here's the inside of it....



& I've drawn back a bit, to let you see what's going on....



In this bearing cover plate sits this bit, which is part of the flywheel....



This is spiral cut to feed any excess oil back into the trough & out via the little copper pipe. I don't know why they went to so much trouble, when the oil just end up dripping on the floor anyway. Maybe the copper tube was supposed to go somewhere else originally. I think the main idea is to keep the oil away from the generator, which would have been direct coupled to the flywheel.

I also have taken a better pic of the inside of the bearing areas in the crank case, this shows the bearing outer & the plain bronze bush seal....



As you can see there are no holes or oil-ways in there, so this must differ from the original design, which must have incorporated those oil holes & troughs. As it is they just run straight to the blocked off outlets I pictured earlier. Weather this happened in the factory or was done at a later date I have no idea. I know the engine has been apart at some point in the past, but there's no evidence it was for this purpose. I'll probably never know, & without another engine in bits to compare, I guess I won't know for a good while.

Anyway, finally (for now) here's some pictures of that wick I found....







I took it to my mum, & without telling her what it was I just asked her "What does that look like to you?" She said exactly what I expected "It's a pipe cleaner". So i guess I'd better see if I can find some. I think they still sell them at the tobacco counter in Tesco.

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Re: Scott PAB Engine Strip-Down

Post by Ianhw77k on Fri Dec 14 2012, 22:41

I've got loads of pipe cleaners, brightly coloured ones for the kids and some of them are weird shapes (they go fatter and thinner). I'll try to steal some and bring them over soon, not sure how absorbent they'll be though, you'll need to do some experimenting.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Fri Dec 14 2012, 23:23

OK, so what can I say tonight????....

Well, I'm getting very close to finishing all my cleaning of bits & bobs, here's just a few of my plastic containers of nuts & bolts, carefully segregated into different groups whilst disassembling. Tonight I've painstakingly cleaned, scrubbed & rinsed every one (there are at least another 2 containers not pictured)....



On reassembly all (or most) of these threads will receive a smear of grease. I'm a firm believer in doing this, as for a start you never know when it may have to come apart again, also it's metal against metal in there, so should be lubricated (unless it's a stud into a block, then it should be bonded).

Anyway, I've cleaned all the casings as well, all my cleaning has been done using a mixture of old fuel, some 2 stroke, some kerosene previously used to flush a fuel tank & some other stuff. This has been allowed to settle, syphoned off then filtered through coffee filter papers. I do the cleaning in an old catering size baking tray & pass all the left over fluid back through another coffee filter for future use. So I end up with different grades of parts wash fluid, the best of which is used in a spray bottle.

Some parts are left to drip dry, leaving a corrosion resistant layer (hopefully), & some are rinsed off with brake & clutch cleaner to make sure they are absolutely clean & will dry properly to avoid dust & debris sticking to them before reassembly.

Anyway, cases....



I've also done some work on the governor. Sadly there are 2 bearings gone here, but I can only afford to replace one (well, truthfully I can't afford that, but that's all I have to spend at the moment). here's a little explanation....

This is the first bearing gone, it's a very small one which sits in a cup, which is acted on by the 2 arms connected to the governor weights....



Here it is in an attempt at an exploded diagram, hopefully you can see what I mean....



It sits on the end of the shaft which pushes outwards, acting against the externally mounted spring, moving the throttle linkages. But I'm not going to replace this one, firstly it would be quite difficult to get it out of that cup, but also I fail to see it's so important, as the governor arms which act on it have captive spinning ball bearings in them anyway, see here....



Also, this shaft doesn't (or shouldn't) rotate, well not much anyway, as it's the governor which rotates, this bearing shouldn't be quite as necessary as the other one which I've had no choice but to replace. So, I've used some loctite to bond the shaft into the bearing & will apply some moly grease before I put it back in.

The one I need to replace is the larger one here....



This one, although spinning freely, has developed some considerable wear. Hopefully you can see it's importance here....



Basically it's the main bearing. It's pressed into the governor body & the centre is wound tightly up against the machined spigot in the timing case by the thread on the bronze bush. This is the cause of the wear on the timing case inner wall which I showed before (here it is again for you)....



So I've ordered this one from Vintage Bearings (very helpful people & they stock many obsolete bearings), it will be posted on Monday, I hope it will be here Tuesday.

So, what else????

Well, I thought I'd cleaned all the cases, cleared out all the oil-ways. I'd cleaned & scrubbed all the nuts & bolts, bits & bobs. I'd also cleaned rinsed, lubricated & careflluy wrapped up all the bearings & the governor. So I thought I might just take a quick look at the carb.

A "quick look" soon turned into this....



Quite an interesting carb actually. It's very much like a motorcycle one, it has the usual throttle slide (not usually found on stationary engines)....



But it also has a separate air slide next to this....



This air slide is cable operated by a turning spiral screw thingy (forget the correct term now)....





But it doesn't seem to do much when running.

The throttle slide is operated by a simple crank mechanism by a single chain link....



I cleaned the whole thing up, piece by piece, in my best parts wash solution & carefully rinsed it all in the brake & clutch cleaner (same as carb cleaner AFAIK) & put it all out to drip dry....



Hopefully I will remember how it all goes back together tomorrow.

One last little note. I expect most of you know this already, but I've come across so many engines lately which haven't had it done, so I thought I would share with you an observation I made recently with these type of float chamber (same on the Lister D & many others).

See in this pic the top of the float chamber, on one side is the tickler plunger, on the other side is a 1/8 whitworth headed bolt....



Do you know what this 1/8 headed bolt does??? Well, it's supposed to be tightened down after the top is screwed onto the float chamber. As you can see here, it is a pinch bolt designed to pull the threads together & stop the float chamber lid rattling loose under vibration....





It literally only needs nipping up, & the float chamber top will never shake loose. Also, it means you don't have to over tighten the top, as many people seem to do. These float chambers are only ever made of soft materials & the fine threads are easily stripped. Many times I've had trouble getting these lids off after they've been over done, & there's no need, as this pinch bolt (originally for motorcycles) keeps the lid tight. It also means you can position the lid wherever you like, so if the tickler plunger is normally in an awkward place, you can rotate the lid round until it's where you want it then do the pinch bolt up.

I expect I'm just stating the bleedin' obvious, but I hope I've reached someone out there who didn't know this.

BTW, I know it wasn't done up on this engine when I got it, but that was because Abes was having some flooding problems with this carb.

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Re: Scott PAB Engine Strip-Down

Post by stationary stu on Sat Dec 15 2012, 12:59

Your doing good work Nuts for someone that wasn't ment to be doing a lot you've nearly got the full engine stripped down into as many small bits as you can Laughing Laughing Laughing

Good luck and hope you remember how it all goes back together, scratch study scratch pale

Stu.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Sat Dec 15 2012, 23:51

Cheers Stu, I'm hoping it goes back together soon, so I don't forget.

I've been busy again today, & I'm very tired now as a result, so I'll try & keep this brief.

I managed to get the carb back together, it's all lovely & clean now. Mind you, it wasn't exactly dirty to start with, but at least I know it a little bit more intimately now....



A bit later on I'll have to strap it to the engine to line everything up & set it all correctly.
Then I thought it might be about time to start getting the crank case halves back together with the crank shaft back in place, so I started by putting the outer bearing back in the flywheel end, then I thought I'd better go on the hunt for some pipe cleaners, which I found at a local newsagents. I did some quick experimenting to see how well they "wick", first with my parts wash solution, then with some clean engine oil, & I have to say I was quite pleased with the results...





So I made one up for the front bearing & put it in.

At some point during the day I also put the oil level sight glass back in the timing case. I know Abes had to replace this as the original was cracked, but as I had disturbed his handy-work I had to sort out some system for sealing it in. Fortunately I have a big box of O rings. I also cut a new gasket for the brass top plate & hopefully it will seal. There wasn't much pressure on the O rings, but it should be enough to seal it....





So, I thought it was about time to get the crank shaft into the flywheel half of the case, but before I did this I took some pictures of its' construction for those interested....







As you can see it's some sort of pinch bolt affair with 2 little dowels in there as well. It suddenly struck me tonight that the 2 little dowels may well have originally been one complete rod, inserted in the groove to align things, then cut off after everything was tightened up. Could this be the case? Maybe to speed up the process & make it easier to build up the crank without the aid of quite so many special tools??? I'm not about to dismantle it to find out, I may have the skills, but I don't have the facilities to do this. (although there is play on the big end, so it may well have to be done at some point).

So I reassembled the crank case halves without too much trouble. I used some "Blue Hylomar" on the joint, I think it's one of the best "instant gasket" type compounds, I do have Stag Wellseal as well, but I prefer to use this in conjunction with a gasket & not on its' own (does that make any sense?)
I'm pretty sure the joint never had a gasket, & there's a lot of evidence of a shellac based compound having been used in the past all over the engine.

Before tightening the cases together I remembered to put the barrel on (no piston) & tighten it down to align the cases properly, then remove it after the cases are tightened together.

I had to give the shaft a little tap on one end to loosen things up a bit & bring the crank webs into line better, but now it's spinning freely by hand (something I worryingly couldn't do when I dismantled the engine). I thought it might be a good time to make up a new barrel gasket, put the piston on & get the top end back together. So I heated the piston slightly with a hot air gun, the gudgeon pin went in a treat, I prepared & Wellseal'd the surfaces, cut myself a new gasket & got it all back together (If I do get a replacement piston ring it doesn't take much effort to get this bit back off again)....



Then I thought I'd better get the throttle control rod, complete with the tiny roller journal bearings, back into its' tube in the timing case. I then put the timing case back onto it's many studs so I could apply the carb & line up the throttle linkages & set the throttle slide height (not the easiest job, I had to come back in & look over old photos of the engine to see how it all went), hopefully it will all be OK....



I've also replaced the brass screw plugs for the oil holes in the crank case, put the solder nipple back on the little copper oil drain pipe & put the engine back onto its' base (it sits on the bench much easier this way). Then I put the crank case drain cock on & set all that up. I don't know what happened to the original brass knob from the pull rod, I expect it's long gone, but I've got it all set up with the nut that was on it plus some copper pipe as a spacer....





Now I've set my sights on the magneto drive shaft (it's bout all I can do now as I'm waiting for the governor bearing & I need to re-dress the starter dog teeth on the other side of things). However I'm faced with a couple of problems, firstly what to do with the flange where the brass bearing carrier meets the back of the timing case, here's a pic of things....



There's, once again, evidence of a shellac based joint compound, but I'm tempted to cut a very thin gasket here.

Then the next problem, there's a missing woodruff key on the shaft itself, here's the bits & bobs that are to go on....



I've put the oil seal into the brass flange & the first (outer) bearing is on the shaft & pressed into the flange, but then comes the sprocket, which has a woodruff key, this is followed by a spacer, a few shims, then the bevel gear for the electric rev counter/exciter for the cycles meter (which works), this gear is missing its' woodruff key & I don't have a spare, so what shall I do?

Should I source a key or just use some of my super strong Locite stud & bearing fix? The cycles meter did work (or rather "does" work), but I seem to remember it being a bit jumpy, but I don't know if the gear has been moving on the shaft or not, it was a pretty tight fit coming off.

As far as the engineering point of view is concerned, the key on any shaft/key combination doesn't actually take any shear loading (or any loading really), if it did it would soon shear itself off, it is only supposed to be there to locate "whatever" on the shaft. But I would feel better if I knew the cog was properly located, although as long as the nut on the end is tightened properly it should be enough.

I would like to dismantle the electric cycle generator as well, as it sounds a bit rough, but I would probably need to drill out screws to get it apart & they are very small screws, it's not a job I feel like doing at this stage & it will probably require some parts or at least some very technical repair job of some kind.

Anyway, that's it for now, I'm so tired I'm making typing mistakes, so it's off to bed. Nothing further to report.

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Re: Scott PAB Engine Strip-Down

Post by matt86 on Sun Dec 16 2012, 10:13

doing a great job matt . that carb is a unusual one on a stationary engine , similar design to the su carbs.

matt

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Sun Dec 16 2012, 10:50

matt86 wrote:doing a great job matt . that carb is a unusual one on a stationary engine , similar design to the su carbs.

matt

Cheers Matt. Apparently the carb is an "Amal TT", it was used on the more sporty motorbikes of the day. Obviously it's got the different throttle mechanism, normally it would just be a cable operating the throttle slide straight from the handlebars. I don't know about the extra air slide though, I'm told it was a feature on the bike carbs as well, but I don't remember ever seeing one myself.

I can see me getting one more day out of this one (which will be today) before I have to wait for my bearing to arrive, which will probably take 2 days due to the christmas post, so I've got to be careful what I start (or finish) in the meantime, don particularly want Ian's Stuart sitting there with its' glistening wet final top coat while I'm cleaning old petrol tanks or filing down starter dog teeth with the dremmel.

What I really need is another shed (& somewhere to put it!).

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Re: Scott PAB Engine Strip-Down

Post by stationary stu on Sun Dec 16 2012, 10:54

Matt, Blue Hylomar is about the best you can get, I think it was made by Rolls Royce, they did all it's development etc.
As for the missing wood ruff key I think I'd either see if I could buy one if not make one up, if that's not going to be easy then give the stud lock a try but I don't know if that will be 100% successful.

You did some good work and made excellent progress keep up the good work mate, and a very good thread to read.

Stu.

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Re: Scott PAB Engine Strip-Down

Post by stationary stu on Sun Dec 16 2012, 10:59

nutgone wrote:

What I really need is another shed (& somewhere to put it!).

Nuts as your aware I'm after another shed, well I've been reading a book all about sheds and there designs. There's some pics of very sexy looking sheds. If you want to get the book it's called " 50 Sheds of Grey" Very Happy Laughing Laughing Laughing Laughing Laughing Laughing Laughing Laughing

Stu.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Sun Dec 16 2012, 11:42

stationary stu wrote:Matt, Blue Hylomar is about the best you can get, I think it was made by Rolls Royce, they did all it's development etc.

Stu.

I heard that too. I believe Stag Wellseal is another very good one, but I never see Wellseal as a product you can use just on its' own (even though you can). To me I think Wellseal goes with gaskets, for a better seal, whereas Blue Hylomar is more of an instant gasket type of compound, although I believe they are both called "Jointing Compounds".

I've even thought about buying a bottle of Shellac (yes, you can still get it), as most of these old engine manuals tell you to paint shellac on to all mating faces before applying a paper gasket (& I believe even without a gasket), which is why sometimes you pull an old engine apart & all the gaskets are really hard & feel almost like Bakelite or something, it's usually just that they've absorbed the shellac & gone hard.

That's the difference though, shellac goes hard, Wellseal & Blue Hylomar should (in theory) never set hard, it's the modern way.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Sun Dec 16 2012, 16:48

Today I've put the timing chain tensioner back together, I know there's no chain in there, but it shouldn't come to any harm & it's about all I can do at the moment. It moves a lot better than it did, so the chain may well be better tensioned than before. Will try to add a pic before I go much further.

Then I got a bit bored & thought I'd have a little play with the electrical generator which powers the "Cycles" meter to give an indication of engine speed. Some time ago I took the cap off this & it was full of white powder, which I assumed was aluminium corrosion & the break-down of the old electrical insulation, anyway, I couldn't go much further at that time due to some very tight, very small, countersunk screws.

However, today I decided it was time to remove these screws & take a look inside. I had to use a very small diamond tipped engraving tool on my Dremmel to sort the screw slots out, with a few taps of a hammer & some GT85 spray I managed to get the cover off & take a look inside....



Not good. The top bearing (a very small caged roller type) was pretty much destroyed, the balls came out during disassembly & on inspection the cage has had it....



The shaft isn't much better



Or the bearing recess in the cap....



My brother was here at the time, he remarked that it looked like a bearing from a fishing reel, it really is that small.

I removed the bevel gear from the end & tapped out the rotor....



That end looks fine. The stator is in a bit of a state though, & I've managed to break a wire connection in there



But I'm sure I can get my best micro-soldering head on & repair that, I just need to be extra careful cleaning it all out. The stator can be removed, but it's been in there so long I doubt I could get it to budge without further damage.

I'm hoping I can solder up the wiring (one of the take-off wires is hanging on by a single strand, then there's the connection I broke) & then make something up for the top bearing. Eventually I should be able to get it back together. It may work again, if not it looks nice. It only really works when the engine is revving hard anyway, so I doubt it's really needed. For now I will just have to make up a cover plate for the hole left in the top of the timing case with this removed.

I bet if I were a real electronics whiz I could make up a modern, solid state, equivalent to fit inside the original case, but I don't even know what voltage it's supposed to give out, I know it's 50 cycles at 3000rpm, & I'm pretty sure, being a 2 stroke & running off the magneto drive, that it runs at full engine speed.

Finally, for now, just as a reference for size (I know my macro photos tend to lose any sense of scale) here's some of these parts next to a standard can of GT85....



For war time technology this really is about as small as it gets. (as far as I know).

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Mon Dec 17 2012, 11:45

I've been fed some information about that rev counter generator on another forum. It seems they were first patented in 1933. So you wouldn't think that I stand much chance of, say, getting new parts or even a replacement then???

Well, take a look here, they still make the damn things!....

http://www.record-electrical.co.uk/products/alternators-generators/

Couldn't believe it! I expect they're bloody expensive, but I'm going to write to them anyway, see what I can manage.

Anyway, yesterday's report (it was too late last night to start typing out), I spent much of the day kind of twiddling my thumbs, just messing with various nuts & bolts, freeing off threads & making sure everything was perfect. I'm fast approaching a temporary dead end with this one, while I wait for parts to arrive.

I put the chain tensioner back on....



The spring loaded plunger on the right hand side wasn't moving correctly in the hole, so I had given it a once over with the dremmel & a small sanding drum, I also gave the plunger itself a going over with some P500 wet & dry (with a squirt of GT to lubricate it), now it moves much more freely.



The end cap for the plunger spring needed a gasket (one of the smallest I've had to make, but an easy one nonetheless)....



The other end just got a smear of Wellseal on the faces before reassembly....



I also re-ground the starter dog teeth, but I forgot to get a picture of it. It's still not perfect, but it'll do. I will probably carry on using the strap starting method anyway, as I've never liked handle start engines much.

I put the timing case cover back on to test the starter dog....



There's some very dodgy parts where the faces meet on the left hand side. It looks like the chain case has had some very harsh treatemnt in the past & has been repaired in places....







When its all bolted up tight the gap is minimal, but there's still a gap there. I'm hoping Blue Hylomar will seal it, as I really don't want to introduce a gasket. The reason for this is that the bearing end caps (which are not just caps but quite long spigots) which go into the case are shimmed so that they meet the bearings exactly (I think). I will have to get some pictures of them & see what others think, but there was no gasket on the timing case before, it was a sealing compound, which seemed to be shellac based.

I also put the trumpet back on the flywheel end....



& I even put the flywheel back on (no idea why, I just had little else to do. Basically I've made a manageable engine into a hefty lump)....



God my workbench is a mess! It's a miracle I can get anything done in here....



But I only ever seem to get things done when it's like this!

Finally, I got some numbers. Here, I think, is the engine number, above which is stamped the word "Jowett" then PAB, the number seems to be 3043....



But there's another marking I've noticed, just to the right of the engine number. It looks like a crown. Here it is again on the rev counter generator....



& here it is again on my brother's Stuart Turner P5XC (which we think was made for MOD use during WW2)....



So, I'm guessing this strange crown stamp marking is found on engines that were destined for war work with the MOD. I don't remember seeing it on my little JAP model 3, & I can't say I remember seeing it on our Douglas generating set, but it's a very long time since I've looked carefully at the Douglas. I see also, each time it appears, there is a horizontal line & a number underneath. There may well be something like this on the Douglas. We'll find out in the spring, when I eventually get round to dragging it out of my sister's garden.

Anyone know???

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Re: Scott PAB Engine Strip-Down

Post by stationary stu on Mon Dec 17 2012, 12:12

nutgone wrote:Today I've put the timing chain tensioner back together, I know there's no chain in there, but it shouldn't come to any harm & it's about all I can do at the moment. It moves a lot better than it did, so the chain may well be better tensioned than before. Will try to add a pic before I go much further.

Then I got a bit bored & thought I'd have a little play with the electrical generator which powers the "Cycles" meter to give an indication of engine speed. Some time ago I took the cap off this & it was full of white powder, which I assumed was aluminium corrosion & the break-down of the old electrical insulation, anyway, I couldn't go much further at that time due to some very tight, very small, countersunk screws.

However, today I decided it was time to remove these screws & take a look inside. I had to use a very small diamond tipped engraving tool on my Dremmel to sort the screw slots out, with a few taps of a hammer & some GT85 spray I managed to get the cover off & take a look inside....



Not good. The top bearing (a very small caged roller type) was pretty much destroyed, the balls came out during disassembly & on inspection the cage has had it....

But I'm sure I can get my best micro-soldering head on & repair that, I just need to be extra careful cleaning it all out. The stator can be removed, but it's been in there so long I doubt I could get it to budge without further damage.

I'm hoping I can solder up the wiring (one of the take-off wires is hanging on by a single strand, then there's the connection I broke) & then make something up for the top bearing. Eventually I should be able to get it back together. It may work again, if not it looks nice. It only really works when the engine is revving hard anyway, so I doubt it's really needed. For now I will just have to make up a cover plate for the hole left in the top of the timing case with this removed.

I bet if I were a real electronics whiz I could make up a modern, solid state, equivalent to fit inside the original case, but I don't even know what voltage it's supposed to give out, I know it's 50 cycles at 3000rpm, & I'm pretty sure, being a 2 stroke & running off the magneto drive, that it runs at full engine speed.

Nuts I have to say if you can get this sorted out and working again you'll be my hero, I think 99% of the people looking at this would say the same yet you are already looking at parts to repair it.

Good luck as I think your going to need it on this one,

Stu.

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Re: Scott PAB Engine Strip-Down

Post by nutgone on Mon Dec 17 2012, 12:40

I might have no choice Stu, but I really need to look into it all & send the company that makes them an email. By the looks of their pictures they still make them, or something very similar. I expect the modern ones are all in metric though, & I'm willing to bet they are very expensive pieces of kit.

Anyway, I finally got some pictures of the bearing caps/cups which go into the timing case cover. There are 2 of them, one for the governor end bearing & one for the magneto drive shaft end bearing. They both came off with quite a few shims, which I cleaned separately....



I've put the shims back on one & taken a close-up....



It looks a lot, but when squashed down there's not really that much there....



This is where they go into the timing case....



This is why I don't want to put a gasket on the timing case, despite the few small gaps on the left hand side. If I introduce a gasket I will be messing up all the shims.

But, I suppose if one was being completely proper about things, you should re'check all the shimming on reassembly anyway. But I'm not entirely sure how this would be measured up on this engine. Maybe I'll have a go when it comes to reassembly.

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Re: Scott PAB Engine Strip-Down

Post by stationary stu on Tue Dec 18 2012, 12:08

Bet it's a days job to re-shim an engine from nothing. I wonder how the factory does it when there new, they must have a rough idea to start with a few but how do you know which end to use them at?

Stu.

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Re: Scott PAB Engine Strip-Down

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