Ive recently rebuilt my top end and after starting it this morning I have a rattle? Or a metal knocking? It's bizarre as I put everything back as it came out albeit replacing gaskets, piston rings and bearing
The piston is the right way, f and arrow facing the front of the bike etc. the power valve and piston havent touched cos its still at standard size. 56mm which I measured. Perfectly matches the old piston and didn't rebore cos guy said it wouldn't need doing as it hast got any score marks or anything. Tried to get a video but my phones being a bellend. It's the usual sound though, that others have said. The power valve is in the same position as before so?
sounds like strip and check time if you only undo the cylinder base bolts when you whip it off you wont need to replace the expensive head gasket base gaskets can be re-used in my experience any knocking/metal sound aint good
I've ripped it all to shreds again and the piston has no score marks, rings are fine, bore is fine. Isit worth putting the old small end bearing back in? Its slightly wider than the one I have, and fits the small end better? Could it be that?
I've ripped it all to shreds again and the piston has no score marks, rings are fine, bore is fine. Isit worth putting the old small end bearing back in? Its slightly wider than the one I have, and fits the small end better? Could it be that?
Almost definityl. There shouldnt a different size in little end bearing. If you ever have play in the bearing you should replace it so if its a different (smaller) size then you will get a rattle.
Yambits stock 2 different small end bearings at the same price. I assumed it was an error on there part and it would be the same part. So ordered the other one. It is slightly narrower than the one that came off. I can't explain the rattle. Almost definitely escalates when I rev the bike though.. So sounds to me like bearing
YOU ONLY NEED A bit of over wear on the bore tho for it to rattle, then soon as it warms up and expands theres even more spave to rattle
did you check the ring end gap with the rings in the bore top and middle
bores never wear true they ovalate twards front and rear
my guess is that the bore is out of spec for a std size piston put the bare piston in the barrel on the bench and wiggle it about check the cylinder to piston clearance with feeler guages to manual spec, u really need a bore guage to check it proply top,middle,bottom/side to side
when checking the top ring gap push the ring down about 10-15 mm past the lip at the top of the bore
Well. The bikes did again. To piston ring smashed into pieces, peppered the dome and top of the piston. Took it into Yamaha and he says it's the piston, was **** and so are the rings. Good old yambits. I'll be ordering a mitaka piston now, getting the bike bored to the next size and matching the piston to the bore now. ****ing waste of 45 quid. I'll post pics later
Yambits are good but I wouldnt use anything but Mitaka or genuine Yam piston kits, I've heard too many bad stories. You can get a mitaka kit from Yam bits for 45 quid delivered through ebay so would be cheaper on their site i believe.
if you only undo the cylinder base bolts when you whip it off you wont need to replace the expensive head gasket 
base gaskets can be re-used in my experience 
any knocking/metal sound aint good 
