I posted this before about the engine missing, and had a couple of responses. I have changed fuel, pulled and checked the carb,checked for air leaks on the intake side., plugs , air chamber, throttle slack adjustment, etc,,,,,,,,,,,,,,,finally I took it to a dealer and the only thing after running it around,(it ran fine) His thought was that these are jetted for sealevel operation and I live at 2700 ft above sea level, runs fine here, but when I take it up into the mountains, ?? at 4000 ft above sea level, it misses and runs really bad.........................Help----Does this sound reasonable. I've had motorcycles before and never had a problem like this happen...............I would like to here some comments on what the dealer said , about how it is jetted> thanks.

 

The air is thinner the higher you go -> less air= less fuel requirment= equals quickly fouled plug. How does your plug look after it starts coughing?

Dont compare a motorcycle with better carbs and stronger ignitions to a quad. In theory they all work the same, in practice, radically differnet.

Try running it on the leaner side and then go to the 4000ft level-> If it runs better or better for a longer period, you have your culprit.

 

actually the plug wasn't wet at all. it looked normal.

 

Actually the important thing is not whether it is wet but what colour is it. Rusty colour is perfect, black is too rich and white is too lean. Too lean is bad, could cause a melt-down.

 

That is very normal as most factories set up machines for sea level operation. The motorcycles you had before were probably jetted better than what you have now. The factory runs these machines rich to keep the risk of engine seizure to a minimum. The higher you go, the richer it will run. So, it makes sense for them to jet at sea-level because if they jetted to high altitude and you went below the high altitude, then the engine would seize from running too lean.