Scott PAB Engine Strip-Down

stationary stu wrote: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.

I've been looking it over today & I might have a plan or two to at least check the shims that are already there.

Just waiting for parts now, can't really continue until they arrive.

Keep us informed once you have your spares.

Stu.

I got the governor large bearing in the post today, but I can't fit it until the other bits turn up, & they won't be posted until Thursday.

Another enthusiast is, very nicely, sending me a small woodruff key for the magneto drive shaft. he's also sending me a brass "Pull To Empty" (EDIT: I see now it is "Pull To Open") knob for the crank case drain rod thingy, a piston ring (which should fit but will need the peg bit filing out of it) & the governor small bearing complete with the cup it sits in & the rod (IE, the complete "Mushroom" arrangement for inside the governor).
I'll see if I can post the image of the bits....



He can't send them until Thursday though, so hopefully I can start reassembly over the weekend. I think they are coming via UPS, so hopefully will be here by the weekend.

I must say I am very pleased, & very grateful, there are some nice people out there still. I know to some it's not much, but these engines are quite rare, & most people would probably hang onto spares for them. Hopefully I can return the favour sometime.

Which reminds me, I must PM a member on here about some bits.....

Great to hear you've got the parts sorted, have you everything you need now to finish restoring the engine? Sounds like your going to have a good Christmas being in the shed all day rather then sitting watch old movies on TV eating mince pies and celebrations.

Stu.

Right, been busy reassembling this one this evening, thanks to Nick for sending those parts through such a reliable delivery service, I get the feeling Royal Mail would've kept me waiting a lot longer.

I haven't really taken any more pics, as there's not been much to photograph. Also, as some of you will already know, my phone has decided to stop sending any emails (something about a certificate problem, which makes no sense to me, as I hadn't changed any settings, but I have now, & it still doesn't work). So I can't get my pics onto Photobucket.

I'm not in the best of moods, twice this engine has tried to throw itself off the workbench when my back's been turned or my attention elsewhere. The first time I got a hand & a leg to it, but a rather large "Cadbury" biscuit tin was there to break its' fall. The second time I was underneath it (trying to secure nuts & bolts) so the top of my head broke its' fall.
Fortunately the engine is fine.

I started by putting the governor back together. I'm not sure if it will still rub on the timing case, but hopefully it won't. I also finished off the magneto drive shaft assembly & got the timing chain on (the crank shaft tapered sprocket was still loose at this time, to facilitate timing). I checked the chain for alignment, as I hadn't noted which way the sprocket was mounted on the governor during disassembly. Fortunately it was fine, I had got it the right way round.

The timing chain tension is an unknown until the case cover is back in place (when it's too late to do much about it). I still think it's too slack, but there's not a lot that can be done, basically I think it's time for a new chain (well, maybe one day).

So it was time to time it. I put the mag in place & got a thin piece of fag paper in between the points. As it's an external impulse I was able to stop it activating quite easily, otherwise I would've just done it backwards (I don't like timing them to TDC on impulse, never seems quite so accurate to me, but it is a good way of checking timing afterwards). Fortunately there is a proper TDC tool in the workshop, which helped, but there are also marks on the flywheel. But these marks must have lined up with something on the generator side of things. So, after putting the flywheel back on temporarily, I got it to TDC with the tool & put a hacksaw blade in the vice on the bench next to the engine. I lined this up with the flywheel TDC mark & used it for my timing. Seemed to work a treat.

Once I was happy with it I carefully tightened up the crankshaft tapered sprocket nut by hand, then, to avoid losing the timing whilst tightening, I put a socket on it (the actual size works for this engine, but often you need one slightly bigger) & gave it a few taps with a hammer, this locks the taper on so you don't lose your timing (you'll find the nut goes loose, then you tighten it up again & give it another tap to make sure the taper's locked). It's a trick my dad taught me to deal with timing up Villiers flywheel magnetos, & it works every time.

I then gave the joint faces on the timing case a good smear of Blue Hylomar, I just hope it seals on the left hand side where there's been some previous damage (mentioned before).

I checked the shimming on the bearing caps & was reasonably happy with it, so they went back on, as did the starter handle spindle assembly.

I decided to put the cowling back on whilst the engine was still on the bench, as well as the carb & the mag. The cowling did have one or two missing fixings, not that they really matter, but I have filled all the gaps & put anti-vibration star locking washers all round (one thing I have noticed about these is their tendency to shake the cowling fixings loose, & I notice a lot of castle nuts with split pin holes everywhere else, most of which now have split pins or wire through them (all except the fixings for the crank case halves, none of which I could get to line up!). So I'm reasonably now that it won't rattle or shake any fixings loose.

Last thing I did before retiring for the night was to bolt it back down to it's chassis & put the flywheel back on (hopefully for good this time), another tap with the hammer & socket here also satisfies me that the taper is locked & I'm not loading it all on the key.

I also lined up all the carb throttle linkages somewhere during all of that. that's not a job I particularly want to repeat, as I'm not exactly sure how I did it, I just seemed to fiddle around & it all came into place.

Just the exhaust to re-fit tomorrow & hopefully I can give her a test run. Oh yes, & I'll need to get some oil for the chain-case before I run her up. I'll just get my usual £3.99 per litre cheapo multigrade I use on all my engines, it's a fairly basic oil & a damn site cheaper than the single grade oils. (but I don't want to get back into the oil debate, it's not reared its' ugly head in a while now, which is nice).

All good news from you Nuts, glad it all went back together with out to many problems lets hope you got the timing right as it's a lot of work involved to re-do it again.
I thought you were going to get it off the bench before adding anything else to the engine or have you a job for when Ian calls round

I don't understand what your going at about? the oil discussion!!! is there some problems with the choice of oil to use just wait till you've been around this forum as long as I have and the same things (like oil) keep popping up

Stu.

Well, she runs! I got her started on the 3rd pull & ticked over very slowly, I shone a torch into the carb & saw the throttle was wide open so knew something was wrong. I gave the mixture knob a twist & she accelerated into life!

If anything it's running a bit faster than before, but there seems to be slightly less mechanical noise than before, although I can still hear the odd whip of the chain against the case on deceleration.

I've decided to try a weaker spring. The last time I tried this it was too slow, so I'm looking for an intermediate spring. The only one I have to hand is my soldering iron stand, so that's going to be butchered for the greater good.

Will keep you all posted how I get on.

P.S. As for the oil debate, I couldn't be bothered going out, so I used what was to hand. A fully synthetic 5w/40 multigrade diesel engine oil! I know it's not right, but it's only a chain & a few bearings, the case is clean & I will be draining it when I get a chance, as I like to flush these things out soon after a rebuild (I did have some flushing oil, but I think it's too thin for this. & why waste my flushing oil when I can waste my dad's diesel engine oil )

New spring has been made (oh well, I never did use that soldering iron stand much anyway ) & she's running a bit slower now. I don't think I want her much slower, although it would be nice just a touch slower. I daren't adjust the length of the spring, so I'll be looking out for a thinner spring of the same length or longer, in the future, as I've got the adjustment screw out as far as it will go.

The alternative is to adjust the throttle to a lower set speed, but that's not much good when it's going to be under load.

Also, I made the mistake of taking the pulley off the flywheel when I had it all in bits. Now it isn't running true, so I'll have to take the flywheel off again & see what I can do. (I wouldn't mind, but there was no need to take the damn thing off, I just wanted to see how it was constructed).

Nuts you get a feeling to how slow or fast an engine should run so until you get it set at that speed you won't be happy.
Also just to remind others that some engines need to run a bit faster as they have no oil pump so need the crank to splash the oil about so the speed is important for those types of engines.

Stu.

stationary stu wrote:Nuts you get a feeling to how slow or fast an engine should run so until you get it set at that speed you won't be happy.
Also just to remind others that some engines need to run a bit faster as they have no oil pump so need the crank to splash the oil about so the speed is important for those types of engines.

Stu.

Also Stu, air cooled engines need to run at a certain speed or faster, in order to keep them cool. If I run this one too slow the fan won't do its' work, especially as this one runs a little differently, sucking air through the cowling, whereas most blow over the fins. These engines were prone to over heating anyway, so I think I'm going to stick to my "intermediate" governor spring for now. If another spring turns up at some point I will get it, but I'm not going mad looking for one. I've slowed it down & the governor is still fully operative, so I'm happy for now.

If I want it any slower I will have to adjust it on the throttle rods, but then the governor will be doing nothing & any load on the engine will not be counteracted by it (so you could, in theory, stall the engine, & it wouldn't be any good for a genny).

I didn't like the "temporary" fuel filter I fitted on this so I bought one of these instead....



I figured I wouldn't use the plastic flexi-hose connectors, I managed to find a couple of brass fittings with the right thread (although the filter has tapered threads & the fittings are parallel, so I used some jointing compound & did them up nice & tight). Basically, I got 2 of these....



I've found some terry clips to hold the filter (although it's so small it could just stay in the line & support itself), & so far I've got this far....





I'm just waiting for Ian to turn up with his coil of 1/4" copper pipe. I would've had enough, but when I fitted the temporary filter & chopped off the wrong end of the fuel line, so the piece I now have isn't long enough. Still, I will hold onto it, it's bound to come in handy some day.

Looks a nice looking filter better then those plastic ones you normally see, but has the tank got that much rust in you need to fit a filter?

Stu.

Trouble is Stu, it's got a kind of sediment trap in the bottom (where a kind of whisk sits, for mixing up the 2 stroke, back in the day), so it's quite hard to get it clean & it's prone to shaking up the crap from this area when the engine is moved about. It only takes a little to get trapped under the float needle & the carb floods.

TBH I would prefer filters on all my engines. None of these old tanks are perfect. Normally I would be happy with the brass gauze soldered onto the tap, but this engine has a different type of tap, built into the tank, so I couldn't do that either.

I've finished it off today & started her up. Really I need to drop the needle again on the throttle slide, as since fitting the air filter she's running a little bit richer. Trouble is I don't know what the original 2 stroke mix was supposed to be on these engines, so I'm running it on 25:1, but it's very smoky. It would probably run on 50:1 but I don't want to risk it as it's not all ball & roller bearings in there, the shaft seals are Oilite bushes.

Anyway, when Ian dropped that copper petrol pipe round last night, he also dropped something else round, so I may be opening up a pretty old thread again with a bit of a follow-up.

Finished off the new fuel pipe today. Took the pics with my new phone, just wanted to see what they looked like really, so here goes....









Just for comparison, here's a similar one taken with the old phone....

Hmm, I can see I need to practise with the settings a bit more.

What's up can you not get her set up now? Stick with it you'll get there it's just patients.

Stu.

Old phone pics look better, maybe keep that one as a digital camera and upload them to the computer like I have to do with my camera all the time.

This new phone has a lot more settings (usually a bad sign, generally more quality items have less settings). I just need to find the correct ones for my kind of pictures.

As for the engine, it starts & runs fine, it's just a little smoky, might drop the throttle needle again, weaken the mixture a bit more.

nutgone wrote:Hmm, I can see I need to practise with the settings a bit more.

Oh your talking about your phone/camera, now it's clear what you were saying.

Stu.

stationary stu wrote:

nutgone wrote:Hmm, I can see I need to practise with the settings a bit more.

Oh your talking about your phone/camera, now it's clear what you were saying.

Stu.

Yeah, I was kind of using this thread as a test bed for my new phone.

OK, so the Scott went to her first show under my ownership last weekend & it didn't go too badly.

It was a 3 day show (bank holiday weekend), the first day I ran the engine a bit, but it was smoking quite badly. I thought it was mainly due to mixture, & it partially was, but I now realise a lot of the problem is the old oil residue left in the exhaust system, which either needs cleaning out or burning off. Well, I wasn't about to dismantle the exhaust system, so I decided to just keep running it & burn it off.

I weakened the 2-stroke mix down to 50:1, I suspect people have been running this engine on 16:1 & probably with engine oil (please folks, don't use engine oil in 2 strokes in this day & age ) & I also dropped the throttle slide needle to it's lowest setting to weaken the mixture even more. It seems to like this, & now the mixture screw/air slide thingy actually does something (so it must've been running rich as it never seemed to make any difference before).

So, day 2; I moved the engine up the row a little (we had 4 engines there) to try & keep the smoke away from the neighbours, but the wind changed & I just ended up smoking out the other neighbours this time! Anyway, the smoke eventually died down a bit & she ran for much of the day.

Day 3 came & I went to start her up but there was a strange noise coming from it & she wouldn't fire up. I eventually discovered it was the magneto, it had dried up & the remains of the old oil on there had gone like resin (this was the only bit I didn't touch during the extensive rebuild ). I completely dismantled it on the rally field (much to the surprise of my neighbours), cleaned all the parts with B&C Cleaner & put it back together. She fired up & ran relatively trouble free for the rest of the day.

The only problem I've been having is some major spark plug fouling, so I've decided to go ahead & order a new set of piston rings. I've got one broken one here & have measured it as best I can, but I can't quite remember the bore size & don't know the ring groove depth (don't even know if they will need the groove depth as I think this measurement is pretty standard). I will be using the "Otto Gas Engine Works" in America, their rings are very cheap, they still work in feet & inches & they carry a massive array of stock sizes. They're certainly cheaper than Cox & Turner for most rings. I will see how I get on with them & post something up about it somewhere else (have heard good reports, but like all these things you don't know until you've dealt with them yourself).

When did you work on this, never seen it on the forum before?

Lewis MacRae wrote:When did you work on this, never seen it on the forum before?

I did this one around Christmas time. Abes had the engine before me & he did all the cosmetic work & pretty much all the restoration, he sold it to me as a non-runner (well, shall we say "A difficult starter") but it looked fantastic.

All I did was strip down & rebuild the engine (& scratch the paintwork ). As it worked out I could've just left it after I de-coked the ports & got it running. The only bits I replaced (from memory) was one bearing (which was probably OK anyway) & a pipe-cleaner oil wick. Think there were a couple of other little bits, but nothing major. Someone from another forum sent me some parts for it as well.

Very interesting little engine, but not everyone's cup of tea. It the history that attracts me, as well as the engineering behind it. Also, there is a register of these engines & there are only about 23 known examples in the country, & most of them are missing their exhaust systems. So it's quite rare & I feel quite lucky to own one. Doesn't make it worth any more money though, but I'm not in it for the money, I'm just happy to own it, this one's a keeper .

Nuts I've never seen a Scott that wasn't smokey it could be like most 2 strokes and needs a load to make her work and thus running better and less smake.

Stu.