Piston clearence

[Reinhoud]

Gents,

 

Anyone knows what an appropiate piston - cylinder clearence would be? (JE pistons)

I measure 78.12 on the piston, and 78.26 in the bore..

That should be more than enough, I think, may be even too much? But I have marks in the  cylinders, and that got me thinking..

 

Bike only did about 3000kms on these cylinders, but during adjusting the carbies she has been running too lean for a while.

It's a GS1000

 

So, what would be good?

 

Thanks

 

 

[Gixer1460]

Wiseco recommend 3-4 thou  or in metric 0.0762 - 0.1016mm. But that will take a bit of running in and is generally considered a bit tight if the engine is to be 'used' ! Around 0.007" or 0.1778mm is the happy medium . . . . . race motors may go bigger but they get more maintenance so. . . . 

[Reinhoud]

Ah, thanks, so mine isn't too bad..

[Blower1]

I have JE pistons in my supercharged EFE (1327cc). Piston to wall clearance is 0.05mm.

I once had EFE cylinder block with Hayabusa pistons & 1127 liners, bored to 0.10 clearance.

It had bad piston slap before the engine temp was really high.

Fuel was/is E85 which is burning cooler than normal fuel.

[Reinhoud]

I got my new pistons in, put one of them in a cylinder, put the lot in the oven on 150 degrees, piston had quite a bit of resistance when I moved it up and down...

Edited August 16, 2019 by Reinhoud

[Gixer1460]

Not surprised - you've used one piston, in an un-restrained block and heated it 'uniformly'. Done this way the cylinders can move around and all of the piston is heated whereas when operating, its primary heat source is only through the crown so the skirt should be somewhat less and maintain its clearances. I'm guessing it's why IC engines are only 30 - 40% efficient - too much mechanical drag!