Piston/Bore Clearance Question

I just received a set of Wiseco 1135 pistons and a "freshly bored" KZ1100 cylinder block which I plan to put onto my M2.

When I tried to fit the pistons into the cyls just for a quick check, it seemed REALLY tight to me. Almost too tight to get the pistons in.

So I took out my bore gauges and micrometer and did my 24 cylinder measurements. Also measured the piston skirts.

Sure enough, the piston/bore clearances came in at .01mm to .03mm. According to the KZ manual, minimum standard clearance should be .043mm to .070mm.

So my question is this. Is this something that a good honing would take care of? The cyls look like they have already been honed after reboring. But I could hone some more. How much bore is normally gained with a standard hone job? Would I need to be somewhat aggressive with it?

Thanks.

Take it back and tell whoever did it you want .0015 / .002"

Jay

I would have to agree with jay, they are way too tight.

not only does it need to be made larger but make sure it is true top to bottom

APE Jay wrote:

Take it back and tell whoever did it you want .0015 / .002"

Jay

I bought it from a M/C shop on Ebay. I talked with the guy and he said a good honing should take care of it. He is willing to refund some of the money to compensate. But what I need to know is can enough additional clearance be obtained by honing, or does it need to be re-bored?

The measurements top to bottom look good and true.

I have, with the right equipment taken .020 out of cyls before, it is a long and slow process, even smaller amounts take some time due to heat from the honing process.
I would not have any issues in rehoning the bores, but make sure whoever does it knows what they are doing so you dont end up with junk jugs

BSKZ650 wrote:

I have, with the right equipment taken .020 out of cyls before, it is a long and slow process, even smaller amounts take some time due to heat from the honing process.
I would not have any issues in rehoning the bores, but make sure whoever does it knows what they are doing so you dont end up with junk jugs

Thanks.

I contacted a local shop that was recommended by another machine shop I have dealt with in the past. He seemed to know what he was talking about, and offered to clean out the bores to the right size for a reasonable cost. I'll take it down to him tomorrow.

AAHHH!!!! E-Bay machine shops... Where all the good deals are:P :laugh: :lol:

APE Jay wrote:

AAHHH!!!! E-Bay machine shops... Where all the good deals are:P :laugh: :lol:

Yeah, yeah, I know.

I took it down to a local M/C machine shop today, and he did a quick cleanup hone and measured the cyls and pistons. He said the clearance is sitting at 2 thou. So I should be good there. He didn't charge me anything. I've found a new best friend.

I think I got a decent deal from the Ebay guy. The Wiseco 74mm 10.25:1 pistons are brand new, and the bored out 1100 block is in decent shape. I ended up paying $220 for the whole thing.

Okay, now I need some advice on ring gaps.

I read the ring end gap document from Wiseco ( wiseco.com/PDFs/Manuals/RingEndGap.pdf ) which said I should have a top ring gap of 4 thou per inch of bore, and second ring gap of 5 thou/inch.

So with 74mm pistons (2.913"), that means I need a top ring gap of abt .0012" and 2nd ring at .0015" right?

So I measured the gaps and got a *tight* 12 thou across the board both top and 2nd rings. In other words, my 12 gauge went in, but it was a tight fit.

How important is it for the second ring to have more gap than the top? If I need to file the ring to gain more gap, is that something I can reasonably do myself without a special ring grinder, and without screwing it up?

Post edited by: Skyman, at: 2007/12/15 13:01

12 is fine, the tighter the better, except for valve guides that that can be purchased on ebay that actually are the right size and not under size for whatreason ill never know,but ahhh the deals.

.oo4 per inch is right and it is fine for both top and second ring, you dont want it to be much tughter than that or the rings will not rotate in the bore

now the fun question, install dry or wet?
I have always installed bikes dry, I am sure the conersation will start

BSKZ650 wrote:

now the fun question, install dry or wet?
I have always installed bikes dry, I am sure the conersation will start

Yes, I am aware of the controversy. The Wiseco installation manual says the following:

Lightly oil the cylinder bore to prevent oxidation and assist with piston installation.

So, I'll probably go with their advice. Sorry.