Different reasons a 2PG runs lean?

[JeffHWV]

I bought an early '89 2PG Marathon with the motor locked up. I tore it down and it looked like it had been in a flood and screwed up the crank bearings. Luckily the crank pin and rod were up and above the very visible water line so they looked good. I did a complete rebuild, 3 new SKF crank bearings, new seals, new piston and rings, (jug was good and in spec), new base and head gaskets, grey Threebond on the crankcase halves, green loctite around the outside of the seals.

The motor ran great for the first tank or two. It still runs good, but every time you come to a stop you have to give it choke to start again, which typically means a fairly significant lean conditon. I have a lot of experience with chain saws and have done several complete rebuilds on 372 and 395 Huskys with no problems so I'm not exactly a beginner with 2 stroke engines but I am not so experienced with the the reed valve type. I went through the Chinese "Mookini" carb with a fine tooth comb, even went as far as to spring $18 on a new one just to make sure. Made zero difference.

Was wondering if a leaky reed valve could possibly cause similar symptoms?

Has anyone had trouble with aftermarket cranks seals? I used the seals that the previous owner had bought. They did not look to be very high quality, but appear to be the same seals that every supplier that posts a picture seems to sell with that same greenish-gold sealant on the outside. I'm not sure but I don't even think that they had a garter on them. I actually went to the trouble of finding a Chicago Rawhide equivalent that would work but was not sure if they would hold up to the rpms and gas, so I went with the ones made for it. I am always careful putting them, learned the hard way long ago, I and am almost positive I didn't screw them up putting it together.

Also, are there any other common causes of vacuum leaks on these motors, something that I am overlooking? I don't really want to try to pressure test it if I can get away with it. I'm going to try the WD40 trick but don't have any at the moment. If it isn't the crank seals not sure where else I should spray it.

I also have another '88 Marathon that does the same exact thing. It hasn't been rebuilt although it is a low hour, extremely well take care of cart. It even has the original Mikuni on it. I can't help thinking the same thing is wrong with both of them as they act exactly the same. Any input on this would be greatly appreciated. Sorry for the long post. Thanks

[cart around]

The fuel pump has a black plastic spacer under it. That could be cracked, or the gasket could be bad.

It goes "o" ring under the pump, spacer, and then gasket at the block. It's a shot in the dark, but you never know.


The only adjustment on the carb is the low speed circuit, but that really doesn't sound like it.

What about fuel line being chafed through somewhere? I just worked on an 83 where the rubber had holes at each end of the steel line.