717 Rotax 717 misfire when throttle open almost full

[micheal3200]

717 Rotax misfire when throttle open almost full
I am not sure whats going on, I have a 96 GTI 717 Rotax that seems to misfire when you get the throttle 3/4 open. We are doing 45 mph on the ski and it seems to start and run fine otherwise, the misfire is only at when throttle opens past 3/4 and its very definite, you back off on the throttle and it goes away, go harder on the throttle and its misfires or sputters, hard to tell. Is there a rev limiter thats engaginging or is it a simple adjustment on the throttle cable thats allowing it to open to far causing this problem, any help you can give me would be greatly apprectated. I have wondered if the timing is off or what, runs perfect otherwise, gets up and goes with no hesitation until you reach the 3/4 throttle point, any insight would be greatly appreciated as I just bought the thing and hoping I did not get taken. Thanks in advance

[Bill O'Neal2]

Re: 717 Rotax 717 misfire when throttle open almost full

I really think you have described a ski that somebody has installed the wrong impellor into.

Your description is though it was geared too low ( not enough pitch on the impellor) causing the engine to rev too high and engage the rev limiter.

Adjusting the throttle cable will have no effect on this problem. You cannot open the carbs too far, they have a throttle shaft stop on them.

The timing is fixed, and probably has nothing to do with your problem.

A remote possibility is that the rev limiter/mpem module is not functioning properly and needs to be replaced, but that would be a rare occurance.

[fedorov5549]

Re: 717 Rotax 717 misfire when throttle open almost full

I've seen the regulater/rectifier cause this symptom also. Maybe try it out?

[schultztec]

Re: 717 Rotax 717 misfire when throttle open almost full

For what its worth, I had this same problem on my HX. It started after a buddy chewed up my impellor by running to close to shore and sucked up a few rocks, dirt etc. After that, the impellor was messed up just enough to over rev the engine at wot, causing the limiter to kick in. Hope this helps

Chris

[Bill O'Neal2]

Re: 717 Rotax 717 misfire when throttle open almost full

Yes the (bad) rectifier can can a high speed miss too. That is definetly a possibility if the pump, wear ring and impellor are in good condition.

[jjsearay]

Re: 717 Rotax 717 misfire when throttle open almost full

Hello, I know it is like 7 years later but did you ever solve your mis fire at 3.4 throttle issue? Mine is doing the same thing. THanks J

[btodd29]

Re: 717 Rotax 717 misfire when throttle open almost full

I had that problem when I was trying to run non-resister spark plugs.