81' GS750E slow to turn over when warm

[Guest]

hey fellas, first post! long story short, I bought this bike with a knock in the motor, turned out to be a bad rod bearing. I tore this motor down over winter and it is now running great. It seems I have worked out all of the bugs except for ONE THING!! The bike cranks very slow when it is warmed up. starts perfect when it is cold. I replaced the starter, and ran power (and ground) straight to the starter from a good battery to make sure it isn't a electrical issue. I have narrowed it down and I believe the problem is in the motor. I also turned the motor over by hand (socket wrench on crank) and it turns over easier than when it is cold. ANY ideas???? I'm stumped. btw this problem existed before I tore the motor down.

[60ratrod]

going to my extensive knowlege about small block chevy engines and slow to crank conditions, it's usually do to a heat saturated starter. heat and electronics do not get along, and when you change to headers on a car, all that heat radiates to the starter and is absorbed. now with it turning easy by hand cold is because metal shrinks when cold and tolerances loosen up a tad, making things turn easier due to the slight extra clearance. did you use a brand new starter when you replaced it or a used unit? one thing that can cause this is dirty and/or corroded electrical contacts as well.

[tom203]

Since you tried different starter motor and have same issue, and wrenching it manually finds no problem, might have something to do with starter clutch or intermidiate gear (the one between starter motor and flywheel gear) binding when cranckcase gets hot.