Hey all. I have a 94 Polaris 300 2 stroke that I bought back in the summer. Since then I've had problems with it running. If and when it decides to run, it starts up on the first crank everytime. When it wont start it acts like it's not even trying to start. Doesn't backfire..spit and sputter...just doesn't do anything but crank over. I went through the carb and everything looks good. I've sprayed carb cleaner at the boots from the air cleaner to the carb and from the carb to the head and didn't find any vacuum leaks there. Its getting fuel and spark (I can smell fuel and I checked spark with a spark tester). Someone I talked with mentioned the crank seals being bad? I don't know but I can't figure it out. Hope someone can help. Thanks

 

Welcome! First thing on a 2 stroke is to check compression. If 115 psi or lower then could be time for a new top end. Seals can also be a problem,which can also cause a low compression reading. That's why "IF" compression is the problem,I'd have the cylinder and piston checked,bored over to next oversize that will clean the cylinder bore up plus replace the seals and be done with it. Then it would run for several more years. OPT

 

Ok thanks for your help I appreciate it. Is there anything else that could be the culprit?

 

Compression and/or possibly the crank seals are the main culprit items, "IF" you're positive the carb is clean,no leaks around the intake adapter,head or base gasket,plus have good spark. The only other thing I would do is to remove the black wire from the reverse limiter module at the circuit board as they will eventually fail and can cause starting problems if they do.Look here under "electrical" on your model for the location of the module and circuit board. http://parts.polarisind.com/Browse/Browse.asp Plus make sure the thumb throttle doesn't have more than 1/8" slack or the etc switch contact points can touch in the throttle housing and cause problems. This engine is fairly simple and you should be able to track down the problem. OPT

 

Thanks for the info OPT. I checked compression and I'm at 110 psi. Would you take the head off or replace the crank seals first?

 

You'll have to have a clutch puller(to get to the left crank seal) and pull the flywheel to get to the one behind the stator on the right side. You have to pull the head then the cylinder(you can do it in the frame) to check the piston out. 9 out of 10 times it's piston damage/clearance problems that are the cause of low compression,but like I said earlier I would also replace the seals since they've taken a lot of abuse also. OPT