1976 All Other Makes Recreational Vehicles yamaha gs300 snowmobile

OLDDODGETRUCK

MEMBER
1976 ALL OTHER MAKES RECREATIONAL VEHICLES
200 MILES

I have a 1976 Yamaha GS300 snowmobile (one cylinder, 2 stroke). It sat for about seven years (my uncle owned it and gave it to me because he didn't use it). When I tried to start it two years ago it would run off starting fluid, but not the gas. I took apart and cleaned the carburetor and it ran fairly well for about a day, and then wouldn't start. I cleaned the carburetor again and again it ran about a day, then wouldn't start. I got tired of working on it, and put it back into the barn. Now this year I am trying to start it again. I bought a used carburetor that I was told was good, and put it in. It still wont run. I have a good spark, my compression was 75, but I put some oil in the cylinder and got it up to 90, fuel is going to the carburetor (I put a primer bulb on it and a fuel filter) but it wont start. I adjusted the screws on the carburetor after it flooded a few times and fixed that. After it flooded I would torch the plug. After I torched the plug it fired a few times then quit. It wouldn't even fire on starting fluid. I am out of ideas. Any advice?

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,289 POSTS

Hi:
We only deal with car issues here. However, I have several snowmobiles and had to try to help. First, 75psi compression is a bit low. It went up to 90 with the oil, so that tells me there is a good bit of wear on the rings.

I have a couple questions. First, is the fuel in the fuel tank new? If it is a couple years old, it most likely won't run the engine. Next, are you sure the plug isn't fouled? If it won't start with starting fluid, something tells me there could be an ignition problem. Make sure the spark at the plug is a good hot blue snapping spark and only sparking at the electrode.

If you have good spark, the plug isn't fouled, and it won't start with fuel or starting fluid, I have a feeling it needs a ring job. I had an old Yamaha SP 292. It had around 125 psi compression.