On my '04 650, when I get to 30 mph in high I get a miss, a blurp for a second. If I keep on the throttle, it will sound like I'm losing a cylinder through the exhaust, clear up and miss again on and off all the way up. My top speed is 52 mph. I'm all stock and ride at 3000 ft. Runs great below that 30 mph. Any suggestions?

 

What mods do you have?

Try some Sea Foam in the gas, that is where I would start.

How about your sprark plugs, and wires?

Air filter clean?

 

What is Sea foam? I have only 700 miles on this thing. tried new plugs, I looked for spark leakage, none found. Rear plug running a little lean, but the dealer told me this is common. I have the stock 122 mains still in. Removed the plunger for the gas vent, so that's clear, air filter is clean. Drained the bowls, checked all jets, checked floats. With the air cleaner off, it will hardly run, is that normal?

 

I am no machanic, but I think it is normal for it to run hard when the air filter is off.

Sea Foam is a fuel additive that cleans the fuel system. It works great, it also takes out water and is a fuel stabilizer. It is safe for all engines, gas, diesel, 2-stroke etc.

This is about the extent of my knowledge, sorry. You can try the ATV technical section HERE as there are a lot of 2004 650 owners there that know the ATV's inside and out. They will hook you up. Good luck to you.

 

did you try cleaning the carbs yet? almost sounds like you could have some dirt inside the carb. and at 3000 feet are you sure you don't have to rejet? and catterman is right they will barely run with the airfilter off.

 

The system is designed to run with the air cleaner on. You remove it and it leans out, bad. You can burn a hole in a piston or the valves if you run without an air cleaner, without a rejet. Rear plug lean, how lean? Just very, very light tan and pure white or whatever color? Lean is not good and this is not normal with a seperate carb for each cylinder.

 

The rear plug is on the way lighter side of good tan plug, it's lean. I'm going to jet it fatter. I can understand the air cleaner being designed to restrict air flow, just wanted to make sure this was normal. What really gets me is the consistancy of the miss at 29 to 31 mph.

 

what gear are you riding in?

 

I ususally ride in low, haven't had a chance to change jets yet. But the problem happens in both L and H. Once past that 30 threshold it happens every 4 to 5 mph past that while being on the throttle.

 

well if you take yours over 30 in low gear often you may have effed something up. L is for 0-30 and H is for 30+. hope you didnt ruin it.