G1 turns over without plug, barely with plug in

[clockdaddy]

I have a G1 I recently resurrected from a junk yard (long story!). The engine is remarkably clean (original) so I concentrated on the miscellaneous problems like missing ignition switch and carburetor. I finally decided to crank it over and see about the engine.
Before turning the key, I pulled the plug and dropped in a few tablespoons of Marvel Mystery oil just in case the piston was stuck. When I turned the key on and pressed the peddle for the first time, it cranked very well. However the next time I pushed the accelerator, the starter locked in and attempted to turn then abruptly blew the main fuse. I tried putting in another fuse and cranking it backwards, in case some rust had it in a bind...still no luck.
I pulled the spark plug and hit the accelerator. The motor cranked over like it should with No problem. After cranking the starter forward and backwards several times, I put the plug in and hit the accelerator and the starter tried to turn over but abruptly blew the fuse again.
Any help, guidance, or advice is greatly appreciated~!!!

[smokindawg]

Possibly liquid locking due to taking up the air space with the liquid of the mystery oil? How's the charge on the battery? Could even be the starter going bad and with the added compression struggling to turn over the engine and shorting internally. Those are my initial thoughts, all of which could be wrong as they are just guesses.

[camaroluvz28]

Agree with smokin, start with battery voltage under a load...if that checks out try tapping the starter with a hammer while its trying to turn over to make sure one of the starter brushes isnt sticking...

[clockdaddy]

The Marvel oil wasn't really enough to stop the piston from moving normally. Remember the engine turns over without the plug in. A thought just occurred to me. What about the exhaust valve? I know from lawn mowers that a valve that doesn't open sufficiently causes a pressure lock. When the valve was given the proper clearance, the lawnmower would turn over normally. Would this same principle apply to the motor in the golf cart?

[camaroluvz28]

Yes it does, The cart utilizes a butterfly valve or "exhaust valve" in the exhaust system to reduce the irregular combustion at low speeds inherent in two stroke engines. When the engine runs under a low load, the butterfly valve is slightly opened so the exhaust flow is restricted.

[paulhut]

The one thing that catches my eye here is that the fuse is blowing. There should not be a fuse between the solenoids, the starter/generator, and the battery. Check the wiring diagrams in the sticky thread.
If the 10A main fuse is blowing when the starter is under load then there is probably a short circuit between the heavy gauge starting wires and the thinner gauge wiring. This might be inside the starter, in or on a solenoid, or it could be damaged wires. Check all of the thick wires that run between the starter, solenoids, and battery and make sure they are connected properly and that the insulation is not cracked or damaged as this can cause a short circuit.
You might also try unplugging the thin green and red wires from the starter and see what happens.
The motor turns over without a plug (I.E. with no load) so the solenoids are working properly in forward and reverse but you should probably verify that they are wired properly anyway. My G1 had some strange wiring issues when I picked it up including an improperly wired reverse solenoid.

[DOOmsman]

Maybe a huge mouse nest in the exhaust system??????

[clockdaddy]

OK, I found the reason for the fuse blowing. The exhaust butterfly was frozen in the closed position, A few squirts of penetrating oil and it's flapping away and the engine now turns over without burning fused. The back pressure of the closed butterfly was the culprit.
Unfortunately the engine still will not run. I have good fire on the spark plug, and when a bit of gas is put in the firing chamber the motor briefly tries to start (very briefly) There is no vacuum! The fuel pump operates with a small amount of vacuum. I took it off and checked it and it works perfectly. I even hooked up an electric fuel pump to attempt to get fuel to the firing chamber. Finally got some fuel to the plug but cart just turns over and never starts! Plug is good, lines are all tight and sealed, ....I'm lost!

[clockdaddy]

Doomsman, you win on this one!! I pulled the exhaust of and the motor started all be it somewhat! As long as I was careful putting pressure on the accelerator, it would run fairly well. Any extensive pressure on the pedal and it would quit running and pop putting out a puff from the exhaust and the carb. Any ideas from here?

[nota]

barbeque