90 marathon bad fuel pump?

[racin161]

Heads up !! be sure to install the rings correct they should fit free in the groves and when installing them in the jug no ring compressor needed make sure the ends of the rings are at the pins and you my want to check the end gap first. Coat the piston and rings with a bit of 2cycle oil and a bit in the jug. MAKE SURE the port in the piston is facing the INTAKE!!!! and don't try to rotate the jug when dropping it down on the case alien it as you install the piston in the jug. I preload the piston in the jug first then drop it on the rod and install the pin. Hope this helps


LOU

[Ezgocruiser90]

I don't mean to bump up an ancient post but I'm still fighting this hog I got the new piston and rings in. It now runs alot better but it loses power going up hills and backfires when I let off the gas especially going down hills, I just replaced the secondary clutch because the one that was on it was shot it helped a little but it still doesn't climb like a cart should, but if I feather the choke it will climb like it should any ideas on how to fix this?

[natew121]

Did this fix the fuel pumping issue . As in do you get steady fuel ive been having similar issues on my 1988 marathon honda gx390 swapped 4 stroke. For me my issue is ethier the gas cap which im pretty sure the vent broke in mine allowing the tank to not have enough pressure to pulse. Or its the piston/ rings . Ive done everything to new few pumps , hoses , spark plug
Cleaned the carb multiple times with a torch tip cleaner .. and.yet anytime you cut it off after running you have to blow air into the gas tank to get any fuel to flow

[dan161]

Does it bog down and sputter yet when climbing hills or just slow down going up hills? My 90 marathon slowed way down so I put a high torque spring in the driven clutch and it helped alot but I'm thinking about replacing the drive clutch as its still not where I'm thinking it should be. Another option is possibly a whole new carb for about $80 and then you know nothing is plugging it or causing the problem within the carb.

It sounds like though that if you have to feather the choke some it might be running to to lean so when you close choke a bit it richens up and gets a bit more gas. Sure sounds like a fuel flow issue to me.

[Ezgocruiser90]

It has good fuel flow from the pump, it mostly just acts up going up hills flat land it drives great, minus the backfiring. It just won't hold rpm going up hill unless I feather the choke. I'll probably order a new carb tonight if that's the next best idea

[Ezgocruiser90]

Well the new carb is on and it runs a hell of alot better! Still backfires and sputters a tad no idea what that's about but atleast it climbs decent now

[dan161]

That's good news. Two things to check for backfire that I found were any leaks in the exhaust system which allows it to pull in oxygen and then kaboom. And then the more tricky is making sure your hearing the switch click before the butterfly on carb opens and also then when you let of the gas pedal the carb butterfly closes all the way. I'm still trying to find that happy point where it closes all the way and then yet opens all the way.

[loudgoldwing]

Cruiser, back the idle stop on the carb out a bit. The backfiring on a 3pg is 99% of the time because the carb idle is set slightly open. This allows a small amount of fuel to spray into the hot combustion chamber, even when your foot is off the gas.

You'll blow out another fuel pump if this keeps up... then, the crank seal.

[dan161]

Originally Posted by loudgoldwing

Cruiser, back the idle stop on the carb out a bit. The backfiring on a 3pg is 99% of the time because the carb idle is set slightly open. This allows a small amount of fuel to spray into the hot combustion chamber, even when your foot is off the gas.

You'll blow out another fuel pump if this keeps up... then, the crank seal.

Or better yet remove it all together. It serves no purpose as your not idling the motor.