Piston and rings

[Guest]

I'm starting my top end rebuild on my 80 850. Got cams out and all cylinder nuts loose with out snapping a single one! I am planning on using pistons and valves from parts bike (see earlier thread) that had only 28,000miles instead of 60,000 like mine. But per earlier thread, the top cylinder cam bolt holes were shot. So I plan to use my cylinder head instead. I'm a little strapped for cash, and have most of what I need except new rings, so wondering if I could use the pistons and rings and bottom cylinder from parts bike on my engine, without creating any problems? I'm planning to deglaze the cylinders, since they look in very good shape. terrylee

[tkent02]

Sure, if the rings are not damaged, and not worn, they should last a long time. Break it in hard just like new rings.

[rustybronco]

As long as they measure within spec , Personally I would use them. I re-did the top end on my 850 which had 33k on it and reused the old rings that came in it. Why should it matter if they are from a different bike? If they're good, they are good.

But, as always, your mileage may vary.

[terrylee]

Thanks for the advice. They look good and even very clean, I will do all the specs on them and see. terrylee

[terrylee]

Everything appears to be within specs. I don't think I can use piston #3 as it has couple of small scratches on one side, one you can feel with your nail. I don't see any scratches inside the cylinder bore though. Hope to order o-rings I need next week and try to get the bike running so I can ride this season, as I haven't been able so far. terrylee

[koolaid_kid]

Can you buff them out?

[tkent02]

Pics of these scratches?

[terrylee]

I think I could buff them out, but not sure how to do it and not mess it up worse. Maybe a dremel with soft wire brush? Or some low grit sandpaper? I'll try to post a pic. later, heading out of town in a while. terrylee

[rustybronco]

Fine grit sandpaper attached to a flat object can be used to remove defects from pistons.

And as said before, pictures are necessary in order to give you an honest opinion of what we would do in your shoes.

[Nessism]

Some skirt scuffing won't hurt anything. I'd be leary of removing material from the pistons if you start sanding on them. At most, knock off any burrs on the edges of the scratches and leave the rest alone.

[terrylee]

My camera does not let me take close up pics. that you can see. I lightly buffed the scratches with 400 wet and dry, very lightly. The scratches are much less and can barely feel when running finger nail across.

[koolaid_kid]

Personally, I would now use 1000 and then use 2000 to get them to a mirror finish.

[terrylee]

Will do thanks! terrylee

[Agemax]

Personally, I would now use 1000 and then use 2000 to get them to a mirror finish.

i would say mirror finish is bad........ oil wont stick to mirror finish, you need splash feed oil to adhere to the pistons or premature wear will occur

[terrylee]

ok, will hold off on that I guess. terrylee