Yamaha g1

[Rwise]

I have a Yamaha g1 that is a 2 stroke it was working fine and then it just quit it is getting gas and it has a good spark and even when you put starting fluid to it it won’t try or it might backfire a very little bit put new spark plug it it it acts like it is out of time or something does anyone know what the problem might be

[Lochlin]

If you are confident that spark and fuel are good then that's helpful. It can still be a few other things, though, unfortunately.

The first thing you are going to want to do is to check your compression to make sure that you didn't lose a ring or a cylinder gasket or something like that. Compression should be around 120 psi if not a bit more.

If that checks out ok then you may have lost vacuum in the crank case. There isn't a good test for that. The only real test is to replace the seals and see what happens.

[checkoutmyjunk]

Originally Posted by Lochlin

If you are confident that spark and fuel are good then that's helpful. It can still be a few other things, though, unfortunately.

The first thing you are going to want to do is to check your compression to make sure that you didn't lose a ring or a cylinder gasket or something like that. Compression should be around 120 psi if not a bit more.

If that checks out ok then you may have lost vacuum in the crank case. There isn't a good test for that. The only real test is to replace the seals and see what happens.

All great suggestions by Lochlin, I would add that a coil can be good one minute and bad the next, same goes for the magneto

[ronperetti]

I too just recently experienced EXACT same problem and troubleshooting results as Rwise on my 1980ish G1 6 passenger Yamaha. My next step was going to be checking magneto as checkoutmyjunk suggested, however, I checked compression and it reads only 35 psig pressure, when it sounds like it should be 100+ psig. So I thought that's the culprit. However, a friend of mine who is an amateur golf cart fixer-upper told me he recently overhauled an older gas cart that still only showed about 35 - 40 psig compression and that it seemed to start and run fine for him. Prior to my cart recently dying, it would usually start and run OK, but always did struggle and lack power when loaded up with 4-5 adults, especially going up inclines, which having only 30 psig compression would explain. I guess my question is can a cart actually start and run "ok" (just lack power) on 30 - 40 psig compression, like my buddy suggests? I'm fairly certain this forum's subject matter experts are going to tell me to fix the compression problem next, then go from there. I'm trying to determine how much more time and money to put into this task. Hate to give up on the ol' cart; it's been fairly faithful and treated be as well as could be expected ... up till now.

[AUTOMAN]

engines will not run below 80psi REAL compression.
You many be using the wrong comp. gage with check valve far away from the cylinder.
cliff