03 Ski-Doo 500 - Why Running Rough at Low RPM's ??

[Turk]

Howdy,

We have an 03 Ski-Doo Rotax 500 that always runs rough, like misfiring, at low RPM's & speeds. Then when it gets up to say, 30 MPH, the engine "instantly" smooths out.

It has new plugs and that didn't help.

Please let me know yer thoughts on what could be causing this...

Thanks!

 

[wileyE]

does it start and idle ok? is it rough accelerating or just at steady speed? how does it compare with other 2 stroke sleds you've ridden? any vibration along with the roughness?

 

[daman]

could be a carb issue,pull and clean,check pilots, blow out
with shop air all jets passages.

 

[Turk]

It starts ok and idles fine. Anything above that up to about 4000 RPM's (it don't have a Tach) is when it runs rough.

Very noticeable, not seen this on other sleds.

Thanks for any help...

 

[daman]

Originally Posted By: tpitcher
It starts ok and idles fine. Anything above that up to about 4000 RPM's

that would be in your pilot and needle circuit.

try cleaning carb..

 

[Brett Miller]

It's a characterist of some 2 strokes with a high state of tune, especially a Rotax.

 

[cmhj]

Many "performance orientated" snowmobile engines will have this issue & it's not a main Rotax trait.

I ran a snowmobile shop for 20 years, worked on and raced snowmobiles for nearly 30, was a Cat, Polaris, Yamaha & Ski Doo dealer for over 15 so I've seen a lot.

It's most noticeable in the 500-700CC engines & more so on the triples with multiple pipes.

However,

This doesn't mean you don't have a problem.

Speculation,

Many times I've seen a sled do what you've described and found it to be a throttle kill switch or slide limit switch being activated. If this has happened after the unit has sat a season "AND" the carbs are clean "AND" the fuel is fresh this is an area to check out.

This issue is mostly Cat related but I've seen it happen on all makes.

Finally,

If this has been a trait since it was new, ride it and enjoy yourself.