1979 KZ750 Scrambler Build

Ran into another issue with the bike last week though, noticed white smoke coming from the pipe and plugs are real black.
I did a compression test and got 90PSI cold and 110-115 hot. Bike odometer says its got 18,XXX miles.
I'll search around on the engines forum but hoping the leak and bad compression are coming from the heads Ive got some viton seals in the mail.

Might just pull the entire engine to work on the heads and rebuild the starter clutch while its off and then I can repaint the frame

Any advice on how to diagnose the issue? I dont have a compressor for a leak down but could ride it to a shop to get checked out.