I just got my head of the spear 4.0 and there is a dark black burnt looking ring on the top of every cylinder. I guess thats where the piston rings stop. Can I sand these down with some fine grit sandpaper? Like 1200 or 2000? Also, I know people polish the intake and exhaust ports, can i do the same to the area behind/above the valves?

BTW what do I use to clean the pistons. Just carb cleaner or brake cleaner or something like that?

Thanks

 

Is it a stain or can it be felt with fingers ?

 

It can be felt. feels kind of like rust only its black and dense.

I'll run down and snap a picture of it.

http://www.flickr.com/photos/9222692...in/photostream

 

The proper tool is called a ridge reamer for this .

 

Those piston holes should also be honed to get sross hatch marks in them .

 

So I cant just sand carefully around the top?

 

If I were to guess, it looks to me like that engine has been burning alot of oil for a long time- this might mean the rings are bad or the valve seals were leaking.

Either way, just clean it up with some industrial cleaner, don't sand anything. If you're not replacing the pistons or rings the lip edge will not harm anything. Everything thing will move the same way it did orginally. If you try sanding it off you could end up damaging the cylinder wall or get comtaminents in combustion chamber. Its not going to hurt to leave it alone.

 

If your not removeing pistons just leave it alone and reasemble it.

 

I am planning on replacing the rings so debris in the chamber is no worry as it would just end up on the basement floor.

 

Ridge reamer then hone cylinders you tube has videos that will help