Re-built Yamaha V4 rattling

[senza170]

Hi everyone again,

I've just got my 140A running properly again, after a complete re-build. I replaced one piston, all rings and bearings now there's a rattling noise coming from the powerhead. When it's stopped, you can grab hold of the flywheel and get it to knock from side to side. It's only a fraction of a millimeter and I was wondering if I've used too much sealant between the two halves of the crankcase. Has anyone come across this sort of thing before? Maybe?

Any Ideas? Rodbolt have you seen anything like this before?

 

[rodbolt]

Re: Re-built Yamaha V4 rattling

I have seen the sealent act as a shim. on that V4 it wont matter on the upper but will on the middle and bottom mains.
if you used the primer it may be an issue,if you did not your most likly chasing a ghost.
did the bottom bearing get replaced?
did the crank get carefully measured and inspected for damage?

 

[senza170]

Re: Re-built Yamaha V4 rattling

I replaced the bottom bearing, even though the old one didn't seem worn. I must admit that I didn't check the crank for run-out, but there were no visible signs of wear.

The re-build came about because the motor wouldn't throttle up above 2000 rpm, so I took it to get it serviced and while it was running in a tank you could hear a knocking noise. Nothing like the noise I have now. I think it was #3 cylinder which had scuffed badly and was picking up, which is the piston I replaced.

Sorry Rodbolt, what do you mean by Primer?

The sealant I used was Threebond 1104.

Thanks