Vibration at throttling off.

[Danbretta]

Hi All,
Just came back from a ride out and noticed a vibration through handlebars and frame when throttling off and tick over. Cant really feel it under load. The engine has sounded a bit deeper tone the last time out. I have just re done the timing and can get no less than 21degrees BTDC (the stator has no more movement in it).
Could the vibrations be down to the flywheel or maybe a crank? I did replace the piston and rings (all allowances within tollerance).
Didnt know whether the deeper hollow sounding tone is normal for a standard 150 LiS.
Any advice much appreciated before I start stripping it down again.
Thanks.

[Nigel. S]

Is vibration accompanied by a rattle sound? If so maybe small end bearing. do you get it when you throttle off to change gear?

[Danbretta]

I think there could well be a rattling sound, whether its link to throttling off I dont know , I'll take it round the block tomorrow and check.

[HxPaul]

Elongate the gaps that the three bolts sit in on the stator so you can get the stator to move more.Before you do this just check your exhaust hasn't come loose at the manifold.

[Danbretta]

HxPaul, I think you were right with the exhaust. Stripping it down to take the cylinder off the exhaust nuts didnt need much to loosen them. By the look of the cowl it appears to have been blowing soot out theres traces in the flow areas at the front of the engine.

I have taken the piston and cylinder off just while I was at it. The piston looks to have some rubbing mark's on the side (piston slap?)

[Danbretta]

I'll check the play in the crank later, does anyone know the tolerances for this? Side to side play. There is no movement forward and backwards on the crank so I'm hoping that bearing is ok.
Maybe a reborn and nw piston/rings required?

[Danbretta]

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