93 XP no start, coughs and backfires.

[davebolo]

I got a 93 xp from a guy real cheap. He gave up on it and bought a newer ski. He never got it running, and suspected coil as all he would get was a cough and backfires. So now it was my turn. The first thing I did was check flywheel position and key. all good. Next is I took off rotax and checked the timing. right at 130 degrees. Had a spare coil, and replaced that too... However, I am having the same issues. I can get a cough and then big backfires.... suggestions on next thing to check? thanks in advance for your input...

 

[seadoodle]

Check the compression

 

[Cheflen]

I got a 93 xp from a guy real cheap. He gave up on it and bought a newer ski. He never got it running, and suspected coil as all he would get was a cough and backfires. So now it was my turn. The first thing I did was check flywheel position and key. all good. Next is I took off rotax and checked the timing. right at 130 degrees. Had a spare coil, and replaced that too... However, I am having the same issues. I can get a cough and then big backfires.... suggestions on next thing to check? thanks in advance for your input...

I would double check the rotary valve timing as that would be what usually makes it cough and backfire

 

[davebolo]

did that took it off had degree wheel, right on 130 mark

 

[Jeffspx]

Just a dumb thought, but your sure its the right valve in there right? I believe it should be a 147 degree valve. If it's right and your sure of timing, maybe its rotary valve clearance.

 

[davebolo]

double checked specs and says 130 for BTDC. I just tried swapping MPEM and same cough issue exisits...Could it be carb related? just trying to start with starter fluid... thx

 

[mikidymac]

First off, never use starter fluid in a 2-stroke as it actually removes any lubrication from the engine parts.

Is the backfire out the carbs or exhaust?

 

[davebolo]

exhaust....

 

[mikidymac]

All of the ones I have seen backfire out the exhaust has leaking needle and seats in the carb flooding the engine.

 

[davebolo]

While I understand that I should not use starter fluid. I wonder if it could be flooding seeing I’m only applying starter fluid.

 

[davebolo]

problem solved, replaced stator and flywheel from spare engine, and ski fired right up...

 

[jpandrews]

Dave, having the same issue with a 93 XP which I bought "cheap" also. Can you tell me if you checked the spark prior to replacing the stator and flywheel? I have what appears to be strong spark, have checked the rotary valve at least 350 times (at least seems like it) and it's the 147 deg wheel set at 130 BTDC. I also rebuilt the top end because it only showed 110 psi on both cylinders. Still shows that so something else may be going on also. Also checked the valve clearance and it's good. Thoughts from yourself or anyone else??