what are allowed cylinder-measurement tolerance?

So here's what my situation is -- the cylinder, after I honed it, I'm getting a 0.3mm (!) piston-to-newly-honed cylinder clearance -- that's measuring the old piston and the newly-honed cylinder.

Now, I never had this one running, I got it non-running so it must've been knocking with mighty loud piston-slap when it last ran.

A 0.3mm clearance, converted to inches, is 0.0118 inches of clearance.

Sounds like I need to bore it to the next oversize *after* buying a new piston set.

Can I get by with just the top end or do I need to do the bottom end too? Could get real expensive.

Ok. Your bores are buggered and need new pistons and rebore.

Going by your user name you have a kz1000 ?
These are bullet proof and unless it has had serious neglect the bottom end won't need touching.
While you have the exhaust off etc i would pull the sump and check that oil pump pick up gauze is clear of obstructions.
Good luck.

Okay good deal, yep this is not the first kz1000 I've owned, I think they must be over-built as modern California police bikes use basically the same engine 35 years on with some upgrades, glad to hear about the bottom end.

I will have a look at the screen -- if memory serves me correctly, you can pull the oil pan off the bottom without removing the engine, I'll get in there with some kerosene or something and flush it out.

Yep!
When the end of the world comes all that will be left is cockroaches and KZ engines :lol:

Theres no magic formula that Im aware of for figuring what a kz motor needs without opening it up and actually checking it.
Ive seen motors with 30,000 plus on them still look surprisingly like new inside if they were taken care of,but at the same time Ive seen motors with 10,000 on them that I was shocked at the amount of wear inside! :sick:
Check oil pump/cam chain and related stuff while youre in there

wireman wrote: Theres no magic formula that Im aware of for figuring what a kz motor needs without opening it up and actually checking it.
Ive seen motors with 30,000 plus on them still look surprisingly like new inside if they were taken care of,but at the same time Ive seen motors with 10,000 on them that I was shocked at the amount of wear inside! :sick:
Check oil pump/cam chain and related stuff while youre in there

Okay will do, I'm hoping I find a clear oil pump pickup screen and no metal in the pan.