91 3pg running issue

[DIESELGREEN]

Hello all, My name is Gary and I'm a new guy here. I'm fairly new to the golf cart hobby, and I am getting to know my little Robin 2-stroke in my new-to-me '91 Marathon. I've been a diesel technician for 10 years, and know my way around the toolbox. Anyhow, after my short introduction, my cart will run for a short while and stumble and shut down. I can close the choke and then it will start and run at about half throttle, but only in reverse. The fuel pump is working, I have already pulled and cleaned the carb, barbecued the muffler, and cleaned up all the main electrical connections. I have ordered a new coil and correct plug wire for it. I have a new wire on it now but it's a makeshift from autozone for now. I am going to check the compression when I pick up a new test set tonight. Any suggestions would be great to help me along. Thanks in advance!!

[kyerik]

If it runs good until it gets hot, then I would guess that the ignition coil or some other electrical component is bad (maybe the igniter). You might want to double check the fuel pump output while it is hot.

[sockethead]

sounds like it's starving for fuel.. do you have a fuel flter installed? perhpas it's clogged...

When mine did that, it was a clogged main jet but you said you already cleaned the carb...
how long is "a short while" ?

[DIESELGREEN]

That's my line of thought too. I have a new coil on the way. I got my new compression tester today, and she's holding a strong 150 psi (score!). I pulled the plug after running it a short while and it was wet. Think I am losing spark. Still find it strange that it will run at part throttle only in reverse with the choke closed almost all the way after it dies out going forward.

[1989Marathon]

I would check the crank seals.

[DIESELGREEN]

They don't seem to have an issue...how detrimental to the operation of the engine is a good crank seal with these?

[1989Marathon]

The fuel pump works off of the vacuum pulse from the crankcase. As the motor heats up, the seals can start to lose their ability to seal the crankshaft, thus losing vacuum in the crankcase.

[DIESELGREEN]

That's the key I'm looking for. I have checked for fuel flow after engine was hot, still pumped strong. I was considering installing a small electric fuel pump to do away with the possibility of a failure of that nature. Looks like I could just cap off the fitting at the crankcase. Any negatives to doing this? I would think it would perform better than the pulse pump.

[DIESELGREEN]

I have a friend with a 2pg that chunked the stock pump for an electric one and it runs strong

[jcurrie69]

Sounds like crank seals if you have to hold the choke on while driving. They tend to wear out over 20 years and are vital for proper operation in those 2 strokes.