Crankcases Turned BLACK!

houseowax · Post by **houseowax** » Sat Nov 17, 2012 10:26 pm

Well, not BLACK exactly, but..
I just tore down my CB77 crankcases and submerged them in water and engine degreaser. I scrubbed them with a brush and after about 1/2 hour of elbow grease they looked almost like new. Until I took them out of the bath - as they dried it became apparent that they'd oxidized pretty badly and they had turned a dull battleship gray.
I was pretty disappointed as I had visions of bright silver. I tried just about everything ( albeit kinda halfheartedly as I was running out of wrenching time) but nothing had the desired effect. Best I could do was Simple Green BBQ Cleaner and a soft brass brush then directly rubbing with vinegar. It got them acceptably brightened, but not what I'd hoped for and they're still pretty uneven and spotty.
Maybe someone has had a similar experience and has an easy remedy? Baking soda? OxiClean?

Ford Guy · Post by **Ford Guy** » Sun Nov 18, 2012 8:27 am

I cleaned mine with aluminum wheel cleaner. THere are different types I used the wheel cleaner just for aluminum and not clear coated aluminum wheels. It was simply spray it on scrub the tough spots and rinse. One needs to be careful mixing all kinds of cleaners it can be dangerous.

48lesco · Post by **48lesco** » Mon Nov 19, 2012 9:34 am

If you have the crankcases apart, most here including me would recommend glass beading with round glass beads to bring back the factory finish. Same for all aluminum parts on the engine that aren't painted or brushed, i.e. crankcase halves, oil pump, cylinder block, head, head cover, side covers, and maybe the cam chain tensioner and carb bodies and bowls.

It's important to clean everything in some kind of solvent first to remove all of the grease and oil that the glass beads might stick to. Glass beading should be performed on CLEAN, DRY parts. I use lacquer thinner in a big tupperware tote because it dries quickly and leaves little residue. After glass beading, wash everything thoroughly with soap and water, flushing all of the oil passages. You may find a local shop with a big solvent tank and glass bead cabinet that would do the whole job for you.