I have a yard machine mtd660 with engine 42a707. I went to start and it just clicks. I replaced solenoid , battery and starter and nothing helped. I tried to bypass the solenoid and cables and hooked a direct cable from battery to starter but all I get is firework sparks. Its as if I have a grounding problem or my ignition switch is bad?? Help please.

Hi,
I would say the pinion on the starter is damaged and wedged in the ring gear of the flywheel. The solenoid is what is clicking and since it is new that would indicate another problem. Try turning the engine counter clockwise by placing both hands on the flywheel screen, pressing down and turning. Then try and see if that changes things. If ii will not turn, that may be a bad omen or the pinion is really jammed.
Peace,
Clarke

Nope-I mentioned the starter and solenoid are new-I can observe the pinion and it does not move. It acts like all the old stuff I just pulled off.

Hi,
I gather that you are saying that all you hear is the click of the solenoid. If there is the click and the pinion spins but never rises to meet the ring gear, it means the battery is connected backwards.
You should have sparks if trying to jump to the starter as it is a high current/low resistance motor.
Please go on!
Peace,
Clarke