What on Earth is going on with my Yanmar 1GM10

[Jake N Eggs]

At higher engine speeds the push rod can potentially come out of the rocker due to the increase in tolerance caused by the exhaust valve being held open. If the push rod catches the rocker in an area outside the push rod pocket it can open the valve too far and potentially make contact with the piston. Bent valves, bent push rods and broken pistons could occur. Decompression is used for slow speed turning, usually for hand crank starting.

 

[Michael Bailey]

Thanks for the information. So why won't it start now. My guess is that motor oil is a poor fuel and there may be lots of deposits left. First do a compress test. You may want to pull the head and have it all checked out. At least it is a small engine so things are small and light. Also winter is coming up so this is possibly a good time to go thought every thing. If there is very little room to work, it may be best to pull the motor and work on it in the shop. Good Luck!

 

[Tally Ho]

At higher engine speeds the push rod can potentially come out of the rocker due to the increase in tolerance caused by the exhaust valve being held open. If the push rod catches the rocker in an area outside the push rod pocket it can open the valve too far and potentially make contact with the piston. Bent valves, bent push rods and broken pistons could occur. Decompression is used for slow speed turning, usually for hand crank starting.

Thanks for the explanation, Good to know!

Greg