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I've noticed a tinny rattle comming from thr top end of my GP200 of late which is most noticeable on the overrun and gets louder when warmed up. I initially thought the flywheel cover was being rubbed by the flywheel because it is a very similar sound. The compression is good and it virtually always starts first time. I'm thinking it might be the little end bearing, does anyone have any suggestions as to what else to look for?

Let's hope that it is not the big-end death rattle that I normally convince myself that it couldn't be.... just before it goes

Adam

I had a cursory look and the noise seems to be comming from the top end. I'll strip the top end next weekend and have a proper look.

I remember about 12 years ago we were riding to Brighton on the Sunday and the day before I thought my engine sounded noisier than usual. Popped round mates and said try my scooter around the block and see what you think. When he came back he told me it was in his opinion far quieter and better running than his !
Next day half way to Brighton the big.end bearing broke up and deposited itself throughout the cylinder walls !!

On the brighter side, last week I saw a loose tool box door fitted with wrong pin emit the similar worrying noise.

Keep your left hand hovering over the clutch..

Beat me to the toolbox door thing, my T5's toolbox makes some odd noises that has me pull over and check much to amusement of other riders lol

^... (lol) yeah, I've experience of the toolbox rattle too!

sounds like it's pinking to me.

It was set up on a Dyno and set on the rich side and the engine was only rebuilt 1500 miles ago with a PM crank. However it did nip up due to an airleak about 1000 miles ago, and whilst I cleaned up the piston and bore I didn't replace the little end bearing.

I thought pinking, what colour is your plug?

Brown

IT'S PINKING.

You need to either look at the jetting or your fuel/oil mixture ratio now.


If it's starting to rattle once it gets warm and particularly under stress, IE: climbing steepish hills etc then it's going to sound like somebody rattling marbles in a can or more like oil boiling in a tin can. You need to rectify this ASAP before you seriously damage anything further.

agree

There is no noise under load but rather when closing down the throttle especially when going down the gears when approaching junctions etc. The noise definitely doesn't sound like the metallic irregular tapping of pinking but much more like the flywheel rubbing on a loose flywheel cover. However it still makes the nose with the cover removed. It is harder to replicate the sound on tick over, but when the engine is warm and revved up and you snap the throttle shut you can hear it from the top end as the rev's reduce. I'd rather not pull the top end apart but I think it's the only way to solve/cure the problem.

Could it be a head gasket leaking if not the little end or maybe the U bend catching on a fin or a stone caught therein?

I checked the cylinder head and base gasket and there was no evidence of oil seepage.

I'd be very interested if you manage to find the source of the rattle. My SIL 200 has had a very similar sounding issue from when I bought it a few years ago.

Over time I have renewed the crank itself together with crank, mag & little end bearings but the rattle is still there.

Mine sounds top-end and from the mag side and is audible on tick-over and through the gears but gets no worse under load so I doubt it's pinking.

I've run without flywheel cowl and dust cover but no change.

The only other thing I can think is that the flywheel has a loose part on it which gets agitated when in motion?

Regards,
Simon.

Whats the tolerances on your Piston to Bore is it piston slap ?

^... good shout

Look carefully at the crown and see if there is a slightly raised edge.

Have you changed your petrol lately.

You say it nipped up a while ago, do you reckon the piston skirt may have got damaged and is now slapping on overrun?