Is it my crankcase seals?

[Chuckwag]

Hey folks,

My 91 Marathon with 2-cycle gas has been impossible to start since right after I bought it a few months ago. So I finally got around to tinkering on it last night.

I found leaky and cracked fuel lines, which I thought explained why no fuel was making it to the carb. So I replaced all the fuel lines, cleaned out the fuel pump with carb spray, then tested the fuel pump by attaching it to a single line from the crank case...it clicked like it was working, so I put everything back together to check it out.

Still no start after a minute of cranking, and still no fuel to the in-line filter. So I took the line from the crankcase off the fuel pump and attached it to a pressure guage to test the crankcase pressure...only two pounds, but at least there was something.

So I reattached the fuel lines and tried again. After a few minutes, I finally got some fuel to the filter, but still no start. So since I know I've got fire, I sprayed some starting fluid into the carb while cranking, and bingo! It started, and drove with very good power except for slow buildup.

I drove it around it for twenty minutes, and it got better the longer I drove it. But tonight, we're back to the beginning...it won't fire.

With my searches on this site, I'm guessing the crankcase seals are shot, causing the low pressure to the fuel pump. Is this my problem...or do you have any other ideas? If it is the crankcase seals, how hard are they to replace?

Thanks for any feedback,

Chuckwag

[tonyton]

Rings and/or crank seals will cause that problem. Test the fuel pump with real fuel and be sure it pumps and not just makes noise. The cranks seals can be pulled from the out side and put back in. You may need to remove the motor for that.
As the engine heats up, the rings and piston will expand and seal better, Thus, more power when hot. Blow by from the rings or leaky seals will stop the pump suction.
You could test the rings with a dry, then wet compression test. If the pressuire is 10 or 20psi higher,wet, the rings are bad or it needs bore. Then you always replace the seals.
Good luck

[Chuckwag]

Thanks for the reply tonyton.

Assuming this thing needs rebuilt, what other options for engine swap might I have?

[tonyton]

Unfortunately, The two cycle rear end has no reverse. The timing in the engine is retarded to make the engine run backwards, like old 2 stroke outboards. You need to stay with a two stroke that has the capacity to spin both ways, or, a rear end with a forward and reverse gear. Newer 2 cycles (boats) don't retard to get reverse, they have transmissions. It's one of those things. a fresh 2 stroke runs good....

[Chuckwag]

Yep, I'm thinking a rebuild is in my future. I've worked on car engines, but this will be new for me. Thanks for the thoughts.