Boring cylinders

[Mitch81special]

Hi all
I have the top end of my 81 apart at the moment to change the cam chain guide as I was getting alot of noise. I took the head and cylinders to be checked out at a machine shop and sure enough I need to bore to first oversize. As I'm new at this I have some questions. Would these cylinders be coated? Do they still need to be honed after boring? And has anyone had experience with pistons and rings from Mike's xs?

 

[jay760]

No they're not coated, normally a good machine shop would hone them as part of the boring process,

 

[Ratranger]

If you only go 1st over, they won't bore. They'll use coarse stones, then switch to finish stones once they are within .001 or so of finished size. Now if you go big bore, the boring setup will come out.

These seem to be well liked pistons. https://www.cruzinimage.net/2017/08/17/yamaha-xs650-0-5mm-oversize-pistons-set-447-type/

 

[hovel]

Worn cylinders requiring even a first oversize refinish are not likely perfectly round any more and honing will not correct this. The machine shop will bore to within a thousandth or so and finish to your clearance specifications with the honing process. Consult both the factory service manual and the piston manufacturer for clearance specs.

 

[Ratranger]

Honing will straighten a cylinder. They aren't using a flex hone, or ball hone, most likely a sunnen hone. Starting with coarse stones and switching to finer stones for finishing will actually true a cylinder and get it to size fairly quick. I've done it at a few different machine shops, it's surprisingly quick even in heat treated stainless.