gap

[murdock]

So I guess it will be like that, the 0.0254 millimetres is 0.25 millimetres, a quarter of a millimetre, 0.0010 inches.

[murdock]

I'm sorry, between the language and the units of measurement this is a mess, would it be 0.58 millimeters? a little more than half a millimeter

[fogrider]

The Honda chart shows a piston to bore difference of .oo1", which is .ooo5" per side.  (half a thou). That's hell of a tight fit ,but that's what the chart says and I believe people have had that done.
How they don't seize up when the piston heats up I don't know .

Careful running in required  !

[K2-K6]

The Honda chart shows a piston to bore difference of .oo1", which is .ooo5" per side.  (half a thou). That's hell of a tight fit ,but that's what the chart says and I believe people have had that done.
How they don't seize up when the piston heats up I don't know .

Careful running in required  !

It's correct, and core to Honda design right from early years. Raised silicone aluminium alloy that gives very low heat expansion rate and matches that of the bores.

We had a good illustrative thread on the subject for a forum member's RS 250 single that the engineer shop insisted boring at larger clearance, producing consistent failure and worthwhile searching for.

[Nurse Julie]

The Honda chart shows a piston to bore difference of .oo1", which is .ooo5" per side.  (half a thou). That's hell of a tight fit ,but that's what the chart says and I believe people have had that done.
How they don't seize up when the piston heats up I don't know .

Careful running in required  !

1 thou clearance on these Hondas using Cruzinimage pistons is perfectly safe and plenty of clearance given OEM Honda pistons the clearance is  . 8 thou inch, or even less.

[Nurse Julie]

So I guess it will be like that, the 0.0254 millimetres is 0.25 millimetres, a quarter of a millimetre, 0.0010 inches.

Correct but your engineer that is doing the rebore should know all this.
Edit, just to clarify, I am responding to your drawing above, where you are showing 0.0254mm piston to bore clearance. But I must reiterate, your engineer should know all these measurements and what they mean.

[Bryanj]

Julie is right, they SHOULD know thatthe clearance is 1thou but a lot f old school engineers insist that is too tight and will sieze. If they try and tell you that go elsewhereuntill you find one who will do it right or you will burn oil.

[murdock]

I doubt that the machinist of the places where I can go are even engineers, so I insist on the measurement in millimeters, since the imperial measurement is not handled in Spain except for plumbing,
If I have that measure, I will insist on that, and if something happens it should be under my responsibility and not that of the machinist

[philward]

So I guess it will be like that, the 0.0254 millimetres is 0.25 millimetres, a quarter of a millimetre, 0.0010 inches.

I feel that we are confusing murdock with our imperial measurements - just to clarify murdock that for your country you should concentrate on the 0.0254mm (which is not 0.25mm unless) measurement

[murdock]

https://www.hondatwins.net/threads/maximum-piston-cylinder-clearance.1976/

[murdock]

creo que ahora si lo he entendido

If the clearance between the wall and the piston is the total clearance, what clearance should I request from the machinist, considering they are aftermarket pistons, 0.001 or 0.002? sounds like the thickness of a hair to me

[Nurse Julie]

creo que ahora si lo he entendido

If the clearance between the wall and the piston is the total clearance, what clearance should I request from the machinist, considering they are aftermarket pistons, 0.001 or 0.002? sounds like the thickness of a hair to me

You are getting yourself so confused for no reason at all. It is the piston to bore clearance which should be 0.0254mm. It really is as simple as that.

[philward]

I think what murdock is confused about is:- is the total bore size 0.0254mm bigger than the piston size (or is that 0.0254mm the clearance at each side of the piston)
(I'm playing the devils advocate for the sake of translation here)

[Bryanj]

You need the hole (bore) to be 0.0254mm bigger than the piston NOT 0.0254 per side but total

[fogrider]

Correct, that's what the Honda charts show - piston size and bore size, the mean difference being .025mm (.001"). That's the dimension  Murdock asked for  with his original drawing. But as has been pointed out, check with Cruzzing, are they happy with that clearance for their particular piston material ?

Hope Murdock has stopped scratching his head now after all this up and down (side to side ?) discussion !

Now, let's start again with ring gaps !!!!