Try using a different brand of fuel with higher octane. Don't use any gasline antifreeze or other additives in that tank. Sounds like severe detonation going on inside. If it persists get it in for a timing check or see how much carbon is on the head/piston causing higher compression and retaining heat. let us know what you find. Had something similar happen to me here a few years ago. Turned out SuperStore uses BARRELS of methol alcohol in their winter gas for our -40 temps. Check your plugs when it happens for color
mxzx, if you have not had the recall done on the carbs, I would as soon as you can. The siphon tube in the carbs are set too low and it will cause a lean condition in the mid-range. The DPM will not compensate for this problem. Doo said that the engines will burn down if the recall is not done.
You might want them to pull the head and see if there is any damage done.
The carbs on the sleds with DPM whent through another processing line during assembly. Somebody on that line was slacking and did not get the tubes set to the right hieght. The carbs for the Legend 500 with out DPM also went through the same line and those are also recalled.
When you hear the noise, stop the sled and look
at your plugs. Are they white? Flecks of aluminum?
If not, and they look black or brown, then I
would check the clamps around your pipe. Maybe
by putting on the choke, you are changing the
vibration of the engine (different RPM's) and
the shield stops rattling. Just a thought.
If it is a squealing noise rather than rattling noise it would be belt deflection or clutches out of alignment. I would have it checked at the dealer. That way it can be a warranty issue. mxzwfo is a dealer and knows of what he says.
Seems like you've covered all the bases on the engine itself. Whats left?
the clutch/ is it torqued properly? Are the springs weak behind the clutch sliders letting them rattle?
engine torque arm/ is it loose?
exhaust/are the sheilds tight? What about ALL the springs? Any streched/missing?
What year and model of machine is it?
I had a similar problem with my 02 800 X . I am not sure about the choke, but I had a bad rattle in my engine and it was the O rings behind the sliding pucks . This problem drove me crazy until i found it. I also found this same poblem on a 01 800 as well. I hope this is all that may be wrong with your sled.
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