Yamaha G1 Only Runs with full choke and full Throttle

[bigstik40]

Earlier, I overlooked the fact that this is a G1. In addition to the reeds, the crank seals, as 750brett also mentioned, could be bad. In a 2 stroke, the crank seals are a very important part of the fuel/air induction system. When they leak, they suck in additional air causing a lean condition. If not corrected, damage (burned) could result to the piston top. Good luck - RAY

[TRP]

When I was looking for an air leak in my 64 t-bird, I used starting fluid. With the car idling, I would spray the starter fluid in or around the area where I suspected a leak. I found the leak when the idle / rpms increased after squirting the fluid at the base of my carb. Sure enough, the gasket between the carb and the intake manifold had a tear in it.

Not sure if this shade tree method will work on the crank seals, but maybe.

Best of luck,
Ted

[85.G3]

Do a compression test

[texastom1]

What should the compression be? I know that when I took it for a ride it had no trouble getting up the hill on my street. That made me think that the motor is still strong and so should have good compression. I ordered the Crank Case seal today. The removal tool is high dollar and I have read that some here have used a long bolt and a spark plug... Does this work? If so does anyone know what spark plug to use and what size bolt I need?
Thanks again,
Tom

[hd72m]

WD 40 will work insread of starting fluid,all it does is stop the air leak.

[texastom1]

I got a new crank case seal for it and tore it all down today, but the seal looked brand new. I looked and followed the oil trail to find that it was coming out of the Base Gasket. So I unbolted the top of the cylinder pulled it up a bit and found a hunk about a 1/4 inch was missing. I assume that if the crank case seal leaking can cause it not to run then the Base gasket leaking will do the same thing. So I ordered the new gasket set and it's back to waiting for parts.

[bigstik40]

A chunk of gasket missing could very well be your problem as that would have the same effect as leaky seals. Your response indicates you have checked only one crankcase seal, but I believe there may be two seals. Would be good to check into that while your into it. Good to see you're tracking the problem down. Good luck. - RAY

[texastom1]

I replaced all of the gaskets in the top end. When I pulled the clutch off to replace the seal it looked new. I replace the reed valve gasket as well. But it still runs the same way. It will only run with the choke out at least 1/2 way and at least 3/4 to full throttle. Even when it is running it acts like it has a miss. It revs up good then it starts spitting and sputtering as it goes up against the governor. If you let off of the gas peddle a little it dies. I have cleaned and adjusted the carb. and cleaned the fuel pump. I can't figure out what to check next. I have even used a separate fuel line with gravity feed to see if there was any difference in the way it runs and there was no change. Any of you guys have any suggestions?

[texastom1]

I also cooked the muffle for a good 6 hours and got a small pile of burnt chunks out of it. I think it is louder now. I have unplugged the black and white wire for testing and it will run ok at full throttle but when I let off some it surges and then dies. I am stumped.

[texastom1]

What happened to everyone? When I 1st posted for help I got several replies but as I get farther into it one has offered any help. I am sure one of the old veterans here that has been working with these carts has run across this before...Any help would definitely be appreciated.
Thanks in advance.