G1 low compression

[ghost1]

Greetings all,

I recently purchased a 1980's Yamaha G1 that runs but is very slow to start and struggles to pull any type of hill. Previous owner has replaced carb and when I got it home, I checked compression which is 90 psi. From what I have read on previous posts, this is low but before I start the tear down, I was hoping someone could confirm that number is low and might be causing those symptoms.. Thanks

[trentofdestiny]

Sounds like you are right on. Since it runs I would recommend checking/replacing the reeds if necessary, before moving to jug and piston.


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[ghost1]

Thanks trentofdestiny... I'm comfortable working on it, however, I've never done anything with reeds.. Is there a way to test, or should I just replace?

[trentofdestiny]

Originally Posted by ghost1

Thanks trentofdestiny... I'm comfortable working on it, however, I've never done anything with reeds.. Is there a way to test, or should I just replace?

If they don't sit very close to the reed block ie there's a big gap then they need replaced. A little tiny gap is ok. I'm not sure the specs. Just replace them if you don't mind the extra $


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[mikeasis]

Originally Posted by ghost1

Greetings all,

I recently purchased a 1980's Yamaha G1 that runs but is very slow to start and struggles to pull any type of hill. Previous owner has replaced carb and when I got it home, I checked compression which is 90 psi. From what I have read on previous posts, this is low but before I start the tear down, I was hoping someone could confirm that number is low and might be causing those symptoms.. Thanks

you need to check the serial number and verify the model year. if its an 82 model year 90psi compression is ok.

[ghost1]

I've checked all around left rear bumper for serial number and can't find a thing. That is where Yamaha shows it being. I'm including a few pictures. Maybe I'm looking in wrong place?

[trentofdestiny]

Mine is missing too. Do you have the plastic tank that says Yamaha on it that goes on the engine shroud? #37 in the diagram. If you have that your cart is 83-89 like mine, if you don't it's 79-82. But that doesn't tell you if you have a 79-81 or 82. Check the number stamped into the jug.




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[mikeasis]

Post better pics of the exhaust. I think I see the cross over pipe so that would make it an 82. J17 would also be stamped in the jug behind the primary clutch

[ghost1]

I found a number stamped on side of engine... J17-002175 ... Not sure if that's what I'm looking for

[mikeasis]

that's exactly what your looking for. The semi bad news is its an 82 aka J17 engine. low compression oddball. it does use some different parts than other g1's. The good news is 90 psi is good compression for that engine.

Don't freak out its a good little engine once all the small things fixed that are common on all g1s. The best thing for this little engine is crank seals if you havent all ready done them. not a bad job to do. $20 ish dollars for the seals and a 20 dollar puller for the primary clutch. this is the source for weird running issues for a 2 stroke engine.


refer to this post for all its differences.
http://www.buggiesgonewild.com/gas-y...g-catalog.html