74 kz 750 twin

Won't turn over with starter or kick start the engine will turn using the 17mm nut on the crank but it is very stiff any ideas

Rusty cylinder walls/rings. Rusty, crusty tranny bearings. Gouged cylinder walls and pistons. Only way to know is to remove the engine and break I down. If you got the knowledge tools, $$ and parts, anything can be fixed.

From what I can see through the sparkplug holes the cylinder walls look good I poured oil in the cylinders and finally got it to turn with the kick start thanks

Just an FYI:
If it's a 74 Kawasaki 750, it's either a two stroke triple, or possibly a four cylinder Z2 (Not clear on years of Z2). The first year for the Kawasaki 750 twin was 76.