79 or 89 yamaha dirt bike

[GANK]

how much compression do these things have I had one dropped off and it wont run even if I spray in gas with a spray bottle not even a back fire. it has spark. I am betting it needs rings and a cylinder. its a 2 stroke and I dont even know the cc. guy said it ran funny then quit. any best guesses? I am getting 40 psi cold with a crappy gauge but its within 10 psi. on my hardest kick.

 

[looneyrod27]

might as well pull the top end off. Most if not all 2 strokes will need in the area of 120 psi cold with the throttle wide open while kicking it over. 40 psi I would have to think the ring is stuck into the piston and quite possibly cylinder damage

 

[CountryRider]

how much compression do these things have I had one dropped off and it wont run even if I spray in gas with a spray bottle not even a back fire. it has spark. I am betting it needs rings and a cylinder. its a 2 stroke and I dont even know the cc. guy said it ran funny then quit. any best guesses? I am getting 40 psi cold with a crappy gauge but its within 10 psi. on my hardest kick.

I got a 1981 kdx 250 running at 135psi... runs strong... U might have a pe something either 175 or 250 or even a yz.... Check the registration plate....