NickelPlated sleeve?

[DieselBoy]

My friend was saying you do not need to hone/bore a nickelplated sleeve in the new CRF/YZFs ever. is this true, i find this very hard to believe if you have scratches/out of round/taper

what advantage does this have ?

[ryanh250ex]

if i'm thinking it's the same as the Nikasil (sp?) cyls, i'm pretty sure they are not to be bored. IIRC alot of bikes in the 80's used nikisil cylinders, i'm pretty sure the tecate 3/4 used them as well.


they last significantly longer than normal cylinder sleeves, the disadvantage is that you have to i'm pretty sure resleeve it every time you do a rebuild.

[GPracer2500]

Cylinders that have a hardened coating don't have a sleeve. The coating is a super hard surface treatment that makes the aluminum of the cylinder not require a steel sleeve.

Typically, yes, you don't have to hone them. The surface is so hard that you CAN'T hone them without special diamond tools that most machine shops don't have. If your plated cylinder is damaged than replating is usually the only option. But you don't have to worry about that much because the coatings are so darn durable.

[DieselBoy]

so say if you sucked some dirt/debris in the intake, would it still scratch like that of a steel sleeve?

[GPracer2500]

Originally posted by DieselBoy
so say if you sucked some dirt/debris in the intake, would it still scratch like that of a steel sleeve?

I think it will, but not as easily as a sleeve. The same reasons that make it impossible to hone with traditional methods are also the reasons it's less likely to be damaged through normal wear and tear.

One thing that I didn't mention is that the coatings are very, very thin. Although with special tools and techniques they can be honed, I don't think it's advisable on most coated cylinders. Removing any of the material is almost like removing ALL of the coating. That's my understanding.

Nikasil and other similar coatings can be deglazed. That's similar to honing except your not actually removing any of the coating. You're just removing steel (from rings), aluminum (from the piston), and other deposites that have bonded to the surface of the coating.

One advantage of plated cylinders is their superior heat transfer--they move heat out of the combustion chamber and into the cooling mechanism better than a sleeve.