How thoroughly to clean BB before re greasing/assembling.

[Spifff]

I've read a bunch of tutorials (including the sticky here) and the only part i'm unsure of is how thoroughly one must clean out all the old grease before regreasing and reassembling.

I've wiped everything down and it is reasonably clean. Wondering if that bit of grease stuck in the bearing ring will contaminate and ruin the new grease or if a bit of mixing doesn't matter and the cleaning step is just mentioned out of completeness?

And a secondary question would be what product to use to clean them. i don't currently have access to any solvents so i'd be buying something and just want to not end up with something overly harsh/dangerous or custom/expensive.

Also doing the rear hub with coaster brake. This is a kids 14" bike. I assume the same question applies there.

Any thoughts appreciated

[DaveM]

A bit of old grease likely won't hurt anything, but old grit or debris trapped in that old grease could. Since you've got the parts opened up, I can't see any real reason not to take the extra couple minutes and get them fully clean Old grease residue could also be covering up damage to the parts themselves that you'll want to see. If the old grease is so hardened up it doesn't wipe out, try using the end of a plastic spoon or something similar as a scraper. Just use something soft enough it won't scratch the metal parts.

You don't need anything too harsh for cleaning normally. Simple Green, window/surface cleaner, rubbing alcohol. Even dish soap will help. The key to is make sure to get all the cleaning solution out before you reassemble. A few drops of any cleaner will destroy the new grease.

[Painkiller]

Engine degreaser from the auto parts store (spray can) works well too and gets the job done fast. Spray let set a couple min. and rinse with water, then dry. It is always better to remove all grease. I find this method even adds an extra sparkle to many parts also. like derailleurs and such. Safe for use on plastic too.