first I will start by saying it is all stock. I never had a problem with it until this winter, my wife and I went to start it and it ran lack crap. backfiring and not idelling. after an hour or so it ran great, then it went into limp mode with the belt light on. I reset belt light and inspected belt it is fine, when compaired to a new one we bought, no wear at all. (only 60 hours on her) replaced spark plugs, cleaned and oiled air filter. drained carb bowls, inspected tank vent, and carb vents. there is nothing blocking my air intake, and when I go for a ride it seems to run really well, and all of the sudden it acts like it is getting choked out when trying to accelerate, bogs really bad. we cant hardly get it home. (I am not talking about belt slippage and it seems to run fine at 1/4 throttle), just wont rev very high. it is not going into limp mode and the 2wd and 4wd works fine. I am at my wits end here, and have very little money to work with. I am very intimidated by the twin carbs, I can barely handle the single khein on my crf450r without having to worry about sinking carbs and such. I have never had a problem with this machine and it has been maintained very well. this just came on all of the sudden and has been going on now for 4 months. I use dry gas so water in the fuel is not an issue. the only thing I am considering is changing the fuel filter and cant seem to locate it(but if it was a filter wouldnt it do it all of the time). if any one can offer me help I would greatly appriciate it. note this only happens after a while of riding, it may work well for 20 minutes, then all of the sudden it starts bogging and I can hardly get her back home. i looked through 137 postings and have not found one that is similer to mine.

 

When mine 650 did what you are explaining it was the needles in the carb had little teeth marks and they were worn out. this can not be your issue with only 60 hours! I'm wondering about your key if it's working properly. You did alot, also if you are in a cold environment you might want to inspect the air vent for your gas tank... next time see if there is pressure by opening your tank. Also check your tip over sensor on the rear right side... good luck. great machine only when runnig right.

 

i did check the air vent on tank, but where is the tip over sensor and how would i identify it and check it. it may be related to the atitude of the quad, ie going down hills seems to trigger it sometime

 

down hills shouldn't trigger it side chabers and up hills and doing wheelies is where I heard/had problems. small little black box that doens't have fins on it is the flip sensor. atitude of the quad I would think the machine would work like crap from day one. and you would know by dirty plugs.