I'm going to assume... 'When starting sometimes compression resistance spinning...' means the engine has stopped but the starter button is still depressed. So that means there is a resistance to the starting system, rather than the compression. The compression is a given so not too many fry their battery upon starting. Say this is a for every action there is an opposite and equal say.
New batteries, fully charged, good connections, no other electrical issues of away kind. Is there a test for the comp release system?
Now say the neg flow begins at ground and ends at the posi side on the jobber. I may be wrong but here is where I apply 'for every' flow that begins, it reverts back to the source it first came. That to me says a bad ground somewhere?
So I would scrub my ground at the ground cable to frame, scrub the relay to cable to starter post and scratch in a new contact onto the jobber. The jobbers being the [starter] post and [relay] posts. I have my ground/posi cables with new, clean contact points to the frame, I am not done yet. I take jumper cables and those 4-ends wind up grounding the trans/engine/frame/ to the battery neg side of the battery are now 4 contact points.
I now start the engine and see if the ground goes to the starter this time, not back to ground or the shortest path melting the post down. I want to start the engine twice so when I remove the jumper cables it made no difference. If the bike starts sluggish, I reconnect two cables back on, it starts sooner again, I have a trans to frame grounding problem. I may have an engine to frame grounding problem. This is one scenario on the basics looking for a bad frame/eng/trans to battery post ground.
I can now remotely hook up the trans only and see how well it starts, or the engine only and how well it starts? I am assuming a belt drive and say the primary was not a ground source from trans to engine to frame kind of connect the dots when chasing for a battery post cook kind of grounding issue.
