FJ1100 won't turn over when under compression.

Low compression, bent valve, jumped timing from a bad belt or worn timing chain, or fuel injectors. Check out all these places

Hi Mark
Sounds like you are doing all the right things.
We used to Load Test a Starter Motor by putting it in a Large Vice and connecting a known good battery with solid fat jumper leads.
When the solenoid throws the cog forward to engage we would use a 2 by 4 block of wood levered against the cog to try and stop the starter from spinning. The wood burns up under load but it quickly proves the Starter is functioning under load. Without using the engine.
Also you could try removing the spark plugs on the engine to allow the compression to escape. Make sure NO sparks around to ignite any fuel vapor.
The engine should spin over easily like this and you can hear & see if anything is binding up.
Hope this Helps!
Good luck!

Check the alignment of the starter gear when it engages the flywheel. It may be going in too tight, or at an angle. It could be binding the starter.

Could try the crank sensor, that is where I would start. Next would be the timing & compression.

From your description it seems that the starter is not engaging to turn over the engine. First ensure all the connections of the thicker cables to the battery, starter and tractor frame are clean and tight. If starter motor is turning but still not engaging it will mean that the pinion on the starter motor is binding on the shaft. You can buy a new starter pinion gear from your local B & S agent.
To replace pinion, remove starter motor from engine, remove old pinion and put on new one and reattach starter to engine. If fuel & spark are right you should be up amd running.

Would be the starter solenoid or relay. Try Yamaha parts or Amazon.

Intake: .004-.006"
Exhaust: .006-.008"


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