Cooling System Cleanup

[kelsorat]

Since my engine is already apart, a flush is out of the question. Are there any safe products for cleaning out the water ports in a Nikasil cylinder and head? The ports have a film of what looks like lime or calcium deposits, and they are not thick. I just want to clean them out.
I do not use tap water, I usually just use Maxima Coolanol or in an emergency I'll use a 50/50 mixture of auto radiator fluid and distilled water. The bike is a 1991 model so there must just be buildup that happened over time.

 

[Rcannon]

I used straight windex with fairly decent results. I wondered about the stuff they sell for automotive use, but I chickened out.

 

[KrackerRacin]

I used SNOBOWL toilet cleaner and it ate the crap right up

 

[Peer Lovell]

A shot of oven cleaner and a scrub with a baby nipple brush works o.k.

 

[kelsorat]

Well, I tried all those suggestions, and these work on everything but the Magnesium Case.
I'm baffled, how in the world does this corrosion come off magnesium?