90 marathon bad fuel pump?
 

Just picked up my 1990 marathon, I knew it needed some work getting into it. Cleaned the carb new belt and oil injection line, when I drive it or have it on a stand it will take awhile to pick up and move then will gain speed like crazy then bog back down. I've found that if I feather the choke while I drive it it seems to run decent. Bad fuel pump? Or am I missing something?

Re: 90 marathon bad fuel pump?
 

You can check the pump easily by disconnecting the fuel line going to the carb, then turn over the motor and see if it is pumping fuel. Could be bad crank seals, or a float adjustment. If it starts good, likely the crank seals are ok. Another thing to check is the vent on the top of the gas tank. Make sure the vent is not plugged. Check the rubber carb boot for cracks.

Re: 90 marathon bad fuel pump?
 

Checked the fuel pump, it seems to be good. I changed the fuel filter and ran the cart out of a gas can of good fuel. It still does the same thing where it bogs down and dies until you choke it but seems to be a little better. I checked the crank seals by spraying carb cleaner around it while it was running there was no change. Any ideas on what to do from here?

Re: 90 marathon bad fuel pump?
 

air/fuel ratio ? has then been messed with or bumped?

Re: 90 marathon bad fuel pump?
 

Had a similar problem when I got my cart took forever to figure it I out but the previous owner had put the incorrect plug in
New correct :roll:Plug and she ran like a dream
Might be worth checking :thumbup:

Re: 90 marathon bad fuel pump?
 

What plug should be in it? I know the guy i bought it from just changed the plug right before i bought it

Re: 90 marathon bad fuel pump?
 

Changed the plug still no change

Re: 90 marathon bad fuel pump?
 

If the oil-gas mixture was off would it cause this problem?

Re: 90 marathon bad fuel pump?
 

The mixture shouldn't cause this issue. I'd take a close look at the carb. Tear it down and clean. While doing this, pay close attention to the needle/seat area, as well as the float. Float should be parallel with the bowl mounting surface. At the very minimum, you'll have a clean carb when you are done.

Re: 90 marathon bad fuel pump?
 

I'm tearing down the carb now for the 3rd time I'm kind of at a loss at what's going on here, anyone know of any aftermarket 4 stroke motors that will drop in and use the factory clutches? I'm gonna get away from 2 strokes if I swap motors I think.