| Did you jump it via the battery connections or directly to the starter motor? If you connected to the battery then it's doubtful the solenoid or the connector Dibble speaks of is the problem.
The sprag clutch is a "one way" bearing. When the starter spins up it turns a gear on the back of the flywheel that has the sprag mounted in it. The sprag grips the flywheel and turns the motor over. Once the starter is disengaged and the engine is running the sprag just sits there.
Your sprag clutch could be on the way out. The extra boost from the jumper battery could be enough to spin the starter motor faster and cause the sprag to grip harder and hence start the engine. It works like a centrifugal clutch............
It's not easy to check as the LHS engine cover needs to come off. Try a new battery. It may be enough to spin the starter fast enough to engage, but it may well give up in the future.
I don't have a reason for it, but especially on hi compression motors, the sprag sometimes plays up on cold engines. Once warmed through and for a few days after they work fine. Leave them for a while and they misbehave. Proabably down to thickened oil??  |