Following is transcription of same quetion posted on another thread and the answers to it. Hope it helps.
AFM

Q
Can anyone tell me what’s the name of the red epoxy that is used in modified Engines crankshaft, or what type of product is it....any help will be appreciated……Gambo94
A
Hi-temp RTV Silicone, gasket maker (ultra black) by "Permatex”…..Wad
Q
But does that RTV silicon get hard like epoxy when dry???
i don’t think so, I have never seen a silicon that can get
as hard as epoxy when dry..... Gambo94
A
Myself and a few other use Permatex Red RTV without any problems for more than a year.
The stuff doesn't have to be hard, it has to stay put……Stefan
A
Oh, and btw, you know what the real reson for this stuff in the JP cranks is?
JP bores out the crankshaft towards the fron (clutch) to make it lighter and the putty is used to seal that hole, or it would change gas flow and crankcase volume negatively…….Stefan