Cylinder size

[tschisi]

Hi!

I have had my cylinder sent to the UK for replating (i live in austria, no replaters here).
Got it back and checked the diameter with the caliper, and it seemed small to me.
I gave it to a bike shop and they measured the diameter at three points.
85,50 - 85,52mm instead of the 86 that it should have.
I died.
I tried my old piston to insert it to the cylinder and it fit without any problems.
So, if my old piston was worn enough to fit a too small cylinder, shouldn?t it be too big at least at the side flanks?
Could the size of my cylinder be ok?
The smallest piston i can find to buy is 85,94.

thx

[tschisi]

I bought a piston to find out if the measurements were crap, and they were! 
It?s a Kawasaki piston.
The dealer couldn?t tell me the size when i ordered it, there?s only one size to order in europe. 
I got it today and it?s a size B piston.
It fits into the cylinder.
I measured the gap with the piston in top position.
My 0,05mm feeler gauge slides into the gap with moderate resistance.
The only thing i?m worried about is the thought to run a B piston in an replated cyl. 

[tschisi]

I played with the feeler gauge again and don?t think the gap is big enough.
The gauge slides in easily until it reaches the piston skirt (?).
Then the gauge can be still slided in, but it?s close to the bend.

Do you think that?s ok when breaking it in carefully, or should i look for a size A piston?

[Polar-Bus]

Hi!

I have had my cylinder sent to the UK for replating (i live in austria, no replaters here).
Got it back and checked the diameter with the caliper, and it seemed small to me.
I gave it to a bike shop and they measured the diameter at three points.
85,50 - 85,52mm instead of the 86 that it should have.
I died.
I tried my old piston to insert it to the cylinder and it fit without any problems.
So, if my old piston was worn enough to fit a too small cylinder, shouldn?t it be too big at least at the side flanks?
Could the size of my cylinder be ok?
The smallest piston i can find to buy is 85,94.

thx

Whenever you send a cylinder out for replating you are supposed to send a new piston along with the cylinder so the plater can finish hone the cylinder to exact piston to cylinder clearence. I'll bet your plater simply rough plated the cylinder, and now you need to finish hone to spec...

[tschisi]

I didn?t know that. 
But there is a cross cut in the cylinder already.
I guess the plater just finished it for an A-piston?!

[tschisi]

I gave the parts to a friend of mine who works as a tool maker.
He measured both parts with special tools and said that the total gap is 0,06-0,08mm.
0,03-0,04mm on each side of the piston, so that would be just fine.
So no i?m confused, i?ll just throw the parts in...
(I?m sorry for that needless thread)

[Polar-Bus]

I gave the parts to a friend of mine who works as a tool maker.
He measured both parts with special tools and said that the total gap is 0,06-0,08mm.
0,03-0,04mm on each side of the piston, so that would be just fine.
So no i?m confused, i?ll just throw the parts in...
(I?m sorry for that needless thread)

Good guess by your cylinder plater. They probably just wen't by Kawasakis recommended min and max tolerences.  .0025" piston to wall clearence is right where you want to be with an OEM cast piston, so you are good to go. Run your premix rich (32:1) for a tankfull, and don't load your engine hard for long periods during top end break in. Have fun !