Hello: I helped a friend of mine build his 440ex with a Wiseco big bore kit. It has the stage 2 hot cam, and an HMF muffler. Everything else remains stock. The bike run great for 40hr, with a dynojet 150main, needle in 3rth position, and fuel screw 3 turns out. Did a plug check and had a brown color.
Yesterday, we were out in the woods and suddenly he started having problems. The quad would not accelerate, like a super rich condition. If the throttle remains static (at any position ej. 10%, 50% or 80% throttle) the motor runs, but the problem is when it accelerates, it hesitates and loosses power, and you can see black smoke coming from the exhaust. Checked the spark plug and it was black.
So I closed the fuel screw all the way to 1 turn out, main jet all the way down to 135 (dynojet), but the problem is not gone!!!
What happened? The place we ride yesterday is the same we always ride, so alttitude did not change, neither temperature or weather.
Any help would be appreciated.
Thanks

 

Check and make sure the float is not stuck. You said you were running a 150 mainjet? That sounds a little lean. 135 would be way to lean. Change the plug first (that very well could be the problem). Good luck!!

 

Thanks Hondanutcase, yes, 150 seemed a little lean to me, but that is what the quad liked (155 would sputter on WOT). But maybe it did because it already had a float problem. Do you know where, and how much to measure in the float for adjustement? (stock carb)
Thanks again.

 

Not sure but, Ive always found that the local Honda dealer service dept. is very helpful.

 

same thing happend with my frind 440ex but than he got the 450r carb like i had and everything was fixed



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99 440ex
84 250r
few mods