Piston scrapes

I pulled the top end off my 80 Kz550 and found this. It had a little knock at idle.. Sounded fine at higher rpm.
The bike has 81000 on it. The cylinder doesn't look that bad. just a hone job maybe.

What does this mean? And what do I do?

Thanks







Post edited by: cnyl, at: 2006/10/01 16:39

Dirty oil ??
Running lean on that cylinder ??
Worn compression rings ??

81k miles check the bores and skirts per the manual.

worn piston and bore will increase clearance causing the piston skirt to slap the bore.
this is likely the sound you were hearing.

oil coated piston skirt slides in bore much like a plain bearing.
if the skirt is galled up, it will continue to rub the cylinder wall.
at the very lease, replace galled pistons and the rings.
used is fine.

if the bores are WAY out of spec and you have the $, get some oversize pistons and rings.
bore and hone to match.
if tight $, scout for a good used block and pistons.

81k miles, I would check oil pump and replace valve guide seals while working on it.

what harry said is possible too but with those miles, i'd go with wear.

-Duck

Thanks guys. So I won't have to split the case? :whistle:

if you're worried about the big end rod bearings making that noise, wiggle the rods gently and see how they feel
real tight or real loose = trouble

That sleeve might look OK, but it is hurt.
Probably time for a 615 kit:P

Jay

Thanks Duck, They feel ok but the pistons feel loose to me wiggled side to side.

615 kit? Hmmmmm. What is that? What do I have to do to install it?

I would look at that piston real close, something has caused it look that way, I would think that the piston is not to size at this point, check the bore , replace the piston and rings, ride the heck out of it

What do you have to do to install a 615 kit? Remove check book and start writing! BWHAHAHAHA

FIRST! LISTEN TO DUCK... rod bearing wear won't go away with a piston kit. SECOND! measure your pistons per your shop manual with an accurate caliper and measure the piston bores per your manual with tee bore gauges... measure in several orientations and depths PER YOUR SERVICE MANUAL to determine not only bore diameter but roundness. Looks like piston slap to me but it is REALLY HARD to gauge looking at photos.

If you measure the pistons and bores you will soon find out if the clearance is within spec and the bores are round. The rod bearings may need to be replaced. I THINK there are ways to check them other than wiggle them if you reference your service manual. I think they may have clearances that can be measured with PLASTIGAGE.

Just tossing money at an engine is usually not a great idea without actually figuring out where the money had best be tossed.

81 thousand miles? I would just about guarantee the bore is out of round at this point. I checked five 750 four cylinder blocks, all with less than 40k miles on them, and every one was out of round.

Cheap fix. Used block/pistons/rings IN GOOD SHAPE i.e. low miles and no scratches in bores. Get the wrist pins and clips too. Label pistons to go back in the same holes.

Would be real handy if you can find someone who has rebuilt a few of these and ask them what to look for and watch out for. Well worth the effort of scouting for that person and if local, taking them out for beer and dinner will be $ well spent.

Thanks. I'll measure this comming weekend. Need to go get some tools..