'56 G80CS Bum numbing Vibration??

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Matchymarty
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Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: '56 G80CS Bum numbing Vibration??

Post by Matchymarty »

Thanks Don.
In a not so nice revelation this morning... I may be on to something, which will require another test ride prior to pulling it down.
Long story short, my father in law flogged the bejeezus out of my '55 G80CS on the weekend, trying to prove that there is 'nothing wrong with the maggie' and cheerfully exclaiming that he sat on indicated 80mph for some time! and.. "I flogged it up and down those hills and it never skipped a beat! There's nothing wrong with it!" Except of course, that when he handed it back to me, there was no oil in the tank, and it was spitting and pouring out of the timing case between Crank case and timing case. Great.

Anyways, he had flogged it that hard, the loctite'd fixings had shaken loose and worked out separating the cases! So I fixed that and rode to work this morning at my normal 55mph, and guess what! A very similar vibration has appeared in the '55 as what I have in the '56!

So riding along the motorway, I felt the engine for vibration... nothing significant.... tank was buzzing like a chainsaw, handle bars similar, seat, painfully vibrating, and yet, if I decel to 50mph smooth as silk, and even accel to 60mph, much better also.

Then, I went in search for the vibes.... reached down to the Crank case, ... nope... head? ... no, but it's transferring thru the frame?! ... then I put the side of my foot on the chain case where the clutch is, and BOOM! Vibration a plenty! finger test on clutch area confirmed massive vibration, and, similarly on the RHS of gearbox... bad vibration... So... quite likely ... clutch related!

Will test the '56 tonight and see, but looks like it'll be wobble or something in the clutch. Wear in the main bearing race centre or something....

To be continued....
Matchymarty
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Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: '56 G80CS Bum numbing Vibration??

Post by Matchymarty »

Finally fixed a gearbox leak and decided to put the '56 back together and ride it on the road again to test my theory about the clutch etc.

The vibrations coming from the clutch area are similar to that of the '55, so, nothing untoward there, although, something that did vibrate more than the '55 ( I think) was the chaincase at the engine sprocket area. Indicating something not so good there.

At any rate, Molly the '56 seems to be burning a bit of oil, running a bit rich, and probably ... ugh I dunno. The Fuel tank is leaking again in the same place that it was before I 'got it fixed'. So tired of people not doing their job properly.

Back to the shed....
Matchymarty
Member
Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: '56 G80CS Bum numbing Vibration??

Post by Matchymarty »

Update:

I just weighed my +0.020" piston. 646.6g complete. According to Don the Guru, his piston ( +0.040" if I'm not mistaken) was 6.02.6g complete. So my piston is 7-10% heavier than it should be, which I imagine is considerable, considering Don's is a +40. Quite possibly, that's not doing any good for my vibration issues.

Time will tell, as I'm going for a full rebuild now.
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