no power - 91' MArathon

[seahunter]

Pardon me if I ask too many questions but this is my first cart and it has me frustrated to no end at the moment. I have no problems sorting out problems of a 225 HP six cylinder 2 stroke but I can’t figure out this simple 1 cylinder job.

My wife brought home a 91’ Marathon that she got for free from a friend. IT had sat in the barn for two years prior because of an unknown problem. I took it apart and replaced all the fuel lines, cleaned the carbs, etc, and got it running. Compression checks out at 125 PSI. Life is good, or so I thought.

The cart starts with ease but has no power. While investigating the power problem I found oil leaking from the cylinder gasket. I changed out the gaskets, cylinder, head, exhaust, reed box, etc but no change in power. Ran the smoke test on the block and found no leakage that I could tell.

In my mind a now 18 year old fuel pump that sat for 2 years is suspect. The vacuum from motor seems adequate but I’m only getting at best a ¼” of head off the pump at the carb. It seems low to me but I have no experience with carts

The other thing of note. The throttle shaft has considerable play in it. I sprayed ether around it with no change in rpm. It seems suspect to me because you typically pick-up a couple of RPM if the throttle boy is leaking too bad.

The other symptom is that choking the motor has no affect at all. Makes no difference if the choke is open or closed.

What is the Max RPM these motors should run? I’m getting maybe 3K RPM with the belt off. Going up any type of an incline down it’s down around 1K or less.

[scottyb]

Opps

[seahunter]

Update:
Pulled the muffler to remove motor from cart. Fired up cart fo the heck of it. Cart ran very well. Compression dropped 15 psi w/o muffler in place.

Installed new muffler and carb. Motor fired right up and ran well but loaded very quickly. Gas and oil running out the exhaust. Unhook fuel line and it runs well until it runs out if gas again. Carb floats OK. Fuel pump OK.

Checked reed unit and found the reed seats cracked and torn. Gaps 1/32" wide in places. Will a bad reed unit cause this behavior? Anyone know where I can find a reed unit for this motor? Discontinued from EZ-Go

[sccowboy]

sounds like the fuel pump diaphragm leaking....but you said it was fine.

[scottyb]

You have done some great diagnostics I'm not much of a 2 stroke guy.... I know those reed valves are somewhere....Lets see where others are getting them....... A quick google search shows that there are a few used ones out there for sale ....

[seahunter]

The latest:
Checked the fuel pump for the third time, not that. Took the muffler back off, no change. Put the old carb back on and it fired right up. It was running pretty rich but it was running.

Humm.....started looking at the new carb. Checked jet sizes, nothing there. Started removing the jets to check for blockage, etc. Got to the main jet and it was loose by about 1 1/2 turns. Tighten up the main jet and put the new carb back on the cart. Adjusted the carb and away we went.

Still getting some spit back thru the carb from the less than perfect reed unit but at least it's finally running. Get a new reed unit in the thing and it should good to go

[scottyb]

Thanks for the follow up~ keep us posted on the reed valve replacement

[sccowboy]

with your diagnostic skills.......you sir will be a tremendous asset to this family! good job!