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Lister knock

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Lister knock

Post by callum12 on Mon Jun 02 2014, 19:12

Hi all,
firstly please excuse the smoke, it was after i honed the bore so it was all still bedding in. It cleared soon after i recorded the video.
anyway, i took my lister to a rally a few weekends ago, in which it ran fine, but because of the rattly trolley i couldn't hear the this knock. Now that i have fixed the trolley rattles the knock is clear.
I dont understand where it could come from, there is absolutely no lift or float in the main bearing and no play in the big or small engine. it is definitely a bottom end knock and almost definitely the bearing or flywheel knock. speaking of which i suppose it could be a loose pulley or flywheel? if so, how can i test this without getting them off and redoing the jib key? or maybe the bearings are pitted? but surely this would be a rumble sound not a knock.
here is a the video to show you what its like (click picture to watch):

any help would be gratefully received since i've got numerous rallies planned!!

Callum Very Happy

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Re: Lister knock

Post by Villiers on Mon Jun 02 2014, 20:21

That is key knock I reckon, can you get the pulley off? If you can then take the pulley off, give the flywheel key a good tap with a hammer and try that, or take the plug out and turn the engine over slowly, if it is a bearing you will hear the "Knock"

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Re: Lister knock

Post by callum12 on Mon Jun 02 2014, 20:29

I haven't tried getting the pulley off, but i will give it a go. It's held on with a square head bolt and a normal bolt so i'm sure i could get it off, though i don't have a puller.
the pulley seems to butt right up to the flywheel so either the pulley has been designed to slot over the key head or the head has been cut off, If it has i will make a drift.
there is no knock when turning the engine over with no plug so i reckon your right.
thanks for that,

callum

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Re: Lister knock

Post by Darryl Ovens on Mon Jun 02 2014, 21:07

Have seen many pulleys with a slot in the hub to go around the head of a gib head key,  for instance many Bamford pulleys are like this.
Another possible source of a heavyish knock in the bottom end is crankshaft end float.  This will vary depending on how level the engine is.  
Easy to check, just give the flywheel/crankshaft a good shake axially (end ways), and see what you can feel and hear.  This knock will often go quiet if the engine has a lean with either the flywheel high or low.  Try it briefly, sometime, when the engine is running, and see if the knock goes quiet.  Take safety precautions to prevent; entanglement or the flywheel touching the floor, (or it will suddenly cease to be a "stationary" engine)     Embarassed

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Re: Lister knock

Post by callum12 on Tue Jun 03 2014, 12:49

i've loosed the set screws with ease so i now need a puller to get the pulley off. I tried a piece of wood in-between the pulley and flywheel but there was no way that would move it.
I have checked for crank shaft float and i have found 0.20mm (0.008") of float on the timing gear side. there is nothing on the flywheel side. where the crank is, you have the piece that engages with the crank web on the timing side, there is a bit of play in that. I know it is normal for it to have play where it engages, but is it normal for it to wobble where the bearing/bushing is (inside the crank)? i think i've explained what i mean Very Happy 
anyway, if anyone knows what the tolerances are for timing side crank end float and the other bit i sort of described.

thank you very much,

Callum

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Re: Lister knock

Post by callum12 on Mon Jun 09 2014, 23:20

the pulley is off, it came off really easily. this made me think, could it have been the pulley thats knocking? because though i needed the puller to get it off the set screws were easy to get off.
i've given the key a whack and it hasn't seemed to have moved, I haven't test run it yet to see if its made any difference. i'm reluctant to do so in case i do more damage. I don't think i will though since i cant find anything wrong.
thanks

Callum

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Re: Lister knock

Post by Villiers on Tue Jun 10 2014, 06:39

Run it, you will never know until you do...

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Re: Lister knock

Post by callum12 on Tue Jun 10 2014, 11:51

yeah, Ive got to fill some water butts for watering the garden today, that involves pumping water from an underground tank. it won't load the engine much but its a good excuse to get her going and test my fiddling!
thanks
callum

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Re: Lister knock

Post by callum12 on Tue Jun 10 2014, 17:16

I ran the lister today, I had to reset the timing as the points had to be gapped again ( their very worn). when i was doing that i noticed that the chain was very slack making accurate timing difficult. when it came to starting the engine I cranked the engine up to speed, took the starting handle out then brought in the fuel incase it kicked back. it didn't start the first time so i tried again but this time it kicked back but i think it was because i didn't crank the engine fast enough before compression.
anyway the knock persists, but i did notice that while running the mag chain actually hits the side of the engine because it so stretched. could this be the cause of the knock? the sound could be being amplified by the crankcase making it sound like its coming from there.
I've already got three shims in-between the mag so i will be getting a new chain, I heard SEP chains are too thick for the sprockets?? if so i will get a old, little worn one. or try and take a few links out of the existing one as i do have a chain link removal tool (for a push bike though).
so i'll sort out the chain some way or another and give you an update,
thanks,
callum Very Happy 

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Re: Lister knock

Post by Foden on Tue Jun 10 2014, 17:32

I don't think that removing a link will help, you need to remove 11/2 links and that will usually be too much. Once the chain is badly worn, as your one obviously is, you will not get a decent tension on it anyway. Much better to get a new one, you need about an inch of slack halfway down the run and rotate it a few times to check for tight spots. You need slack all the time or you will put pressure on the small bearings in the magneto and destroy them. Also make sure you have the closed end of the split link clip facing the direction of travel and that the mag and bottom sprockets are dead in line, use a ruler or straight edge to adjust the magneto position.

Pete.

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Re: Lister knock

Post by Darryl Ovens on Wed Jun 11 2014, 01:44

Plus if a short chain has stretched that much it's pitch no longer matches that of the sprockets and causes the chain to ride out on the sprockets and wear the tips of the teeth.  
In NZ we can still get imperial pitch chain from the engineering supply shops, I would guess that would be the same for you.

Cheers
Darryl

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Re: Lister knock

Post by callum12 on Wed Jun 11 2014, 17:17

Hi Darryl,
I knew that with cycling bikes a worn chain will wear the sprockets to the new pitch of the chain meaning that when a new, correct pitch chain in put on the worn sprockets the pitch of the chain and sprocket will no longer match and will cause the chain to jump. so i hope that this isn't the case with my lister.

you can still see the machining marks on the sprocket teeth tips so i don't think their worn.
I'll have a look for imp chain, machine shops are/have died out here though.

thanks
callum

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Re: Lister knock

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