Author Topic: Vibration from the engine or is it?  (Read 1559 times)

Offline BSA500

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Vibration from the engine or is it?
« on: 14.01. 2012 17:03 »
A little while back I had issues with some crank shims breaking up. Sorted it out and for a while every thing was ok in the BSA world. Then it reappears but different only at certain revs unlike the shims which was all the time and horrible. Mister paranoid here thought shims again so took off the sump plate no derbis, took off the primary case no play in the crank strange?. So I checked the clutch no in and out play but then tried up and down oh bugger there is play. My question is would this be wear in the bushes(i suspect it is as there seems to be no movement in the gearbox sprocket) and how easy are they to sort I think there is two bushes in there. Never ending is it when you use these to do 150 miles a week but she did pass the MOT today,oh and on the electrical page my woes continue with a dead dynamo.
Andy
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Offline muskrat

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Re: Vibration from the engine or is it?
« Reply #1 on: 14.01. 2012 21:20 »
 G'day Andy,
                 might sound obvious but my first inspection would be all the engine/gearbox/mounting plates bolts/nuts. Then ignition timing (same both sides).
How much up & down play is there? I would consider 1mm at the end of the shaft ok but 2mm too much.
Cheers
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Offline BSA500

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Re: Vibration from the engine or is it?
« Reply #2 on: 15.01. 2012 12:06 »
I have checked all the engine mounts and timing. Its difficult to judge the amount of play beyond thinking thats alot of play when I tried it. I repadded under the petrol tank that helped the secondary vibration alot but I am still getting a fair bit through the footpegs at certain points in the rev range. I think its the sleeve gear bushes as I noticed some play when trying to stop a gearbox oil leak and discovering the oil was leaving the box down the mainshaft. I am sure the play has increased since then.
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Offline wilko

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Re: Vibration from the engine or is it?
« Reply #3 on: 15.01. 2012 19:26 »
I've never seen a brit clutch that didn't wobble? Check your primary chain for broken rollers or adjusted too tight.
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Offline A10Boy

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Re: Vibration from the engine or is it?
« Reply #4 on: 15.01. 2012 20:19 »
The clutch will move 1/16 or so and that is normal IMO. There is movement designed into it when you consider the clearances is the sleeve gear bush etc.

I would check the timing side main bush just to be on the safe side.

HTH
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Offline BSA500

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Re: Vibration from the engine or is it?
« Reply #5 on: 15.01. 2012 23:01 »
I recently had the bottom end apart to replace the shims - less than a month ago- and everything was fine besides the shims of course. I also replaced the drive side bearing while inside the engine. There was no play in the timing side bush so thats out of the equation. The clutch when assembled does not actually wobble its quite stable it only moves about when the clutch lever is pulled in as you would expect. The movement is up and down not side to side wobble and as I said alot of oil escapes the box down the mainshaft esp as my A7 is always parked on the side stand.
It just feels wrong and I think I feel the clutch causing the vibration I am not sure though so any suggestions are welcome. Its very annoying as i travel 30 miles a day to work so the massage to my feet is getting to me *conf*
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Online chaterlea25

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Re: Vibration from the engine or is it?
« Reply #6 on: 16.01. 2012 09:51 »
Hi All,
If there is 1/16th play in the sleeve gear bushes it means there is something seriously WRONG *eek*
there should not be more than a couple of thou
Have you checked that the clutch centre is tight and fitting the taper properly?
I have found a couple of times on various A's that the gearbox mainshaft is bent *ex*
this causes a clutch wobble and the primary chain runs tight/slack
Operate the kickstart with the clutch pulled in and see if the chain tension alters
HTH
John O R
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Offline A10Boy

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Re: Vibration from the engine or is it?
« Reply #7 on: 16.01. 2012 13:42 »
Just for the avoidance of doubt, I didnt say there was or should be 1/16 play in the sleeve gear. What I said was that the clutch will move 1/16 or so and that is normal IMO. There is movement designed into it when you consider the clearances in the sleeve gear bush etc.

The sleeve gear bush will have clearances as will other components which make up the clutch assy and obviously, these added together they allow the clutch to move.

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Andy

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Offline Topdad

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Re: Vibration from the engine or is it?
« Reply #8 on: 16.01. 2012 15:10 »
Andy, my gearbox was completely knackered with some symtoms as you describe, oil p****** out of the sleeve bearing , VIBRATION but only at times and  I thought initiallyy at the time it could be the clutch out of line etc. It wasn't on striping the box everything was worn out.when rebuilt and ridden again ( only 2 weeks ago ) absolutely amazed at the difference really smooth. Also be interested to hear how things pan out re Johns comments re a bent mainshaft ,the abuse these things took in there early years beggars belief. Best wishes BobH
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Offline BSA500

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Re: Vibration from the engine or is it?
« Reply #9 on: 16.01. 2012 15:41 »
The box is in pretty good condition. The cluster is from a C12 and nearly unworn a newish main bearing etc but the only thing I have not attempted to replace is the sleeve bushes and I have owned her for over twenty years so perhaps I should now:)
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Online KiwiGF

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Re: Vibration from the engine or is it?
« Reply #10 on: 18.01. 2012 05:35 »
I've done the sleeve bearing job, a bit fiddley drilling the oil holes in the bushes-which I did before pressing them- but not hard to do the job with some 10mm studding a vice to press the bushes in with and spacers of right diameter

The odd thing was that immediately after fitting the new bushes the mainshaft was a good fit with just enough clearance which I thought was great but a week later the bushes had shrunk and needed to be reamed a couple of thou bigger

I guess there must have been some stress left in the bushes after pressing them which relieved over the week and caused the gear to shrink if you see what I mean
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Offline BSA500

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Re: Vibration from the engine or is it?
« Reply #11 on: 18.01. 2012 16:52 »
I have a spare sleeve gear so I will press the new ones in and measure them against a spare mainshaft I have as well. Then I can see if mine shrink as well. I think I ought to repharse my original question and ask would worn sleeve bushes cause vibration?
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Online KiwiGF

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Re: Vibration from the engine or is it?
« Reply #12 on: 19.01. 2012 05:30 »
In my opinion I think any vibe from worn gearbox bearings would be small compared to that from the engine and also quite a different sort of vibe I.e more related to road speed than engine speed

The size of the rotating parts in the box are much smaller than the engine and the gearbox rpm is also much less

Just my opinion!

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Offline BSA500

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Re: Vibration from the engine or is it?
« Reply #13 on: 19.01. 2012 12:59 »
I feel the vibration is more to do with the whole clutch asembly being able to move around due to the worn sleeve bushes rather than the ball bearings. Its driving me mad because last night it was awful I could of sworn the bottom end was going to drop out!!. So I checked the sump plate etc for what I believed was destroyed shims again and that was clean no debris. This morning it was fine ish still some vibration but no where near the level last night what the hell is going on????
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