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help!!!
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Posted by: dns1764

i went riding today. my 300ex ran fine, but i shut it off after about 45 min. when i got back on, i could not go past half throttle. if i did the bike would die and backfire a few times in the process. there was also a bit of black smoke.

Posted by: sd1

Did you pull your plug and see how rich it was running?....Did you check your air filter? is it backfiring past half throttle or just bogging out?

Posted by: dns1764

the plug was black. as for air filters i'm running a k&n knockoff which is fairly new. i think its backfireing past half

Posted by: sd1

hmmm..could be quite few things....first i'd pull the plug....clean the air filter......also pull off the carb bowl and make sure there is no dirt in the carb...also make sure your air mixture screw is set properly......after everything is cleaned up ...pop in a new plug and see how it runs...

Posted by: dns1764

ok i'll try the plug tomorrow. thanks for the help

Posted by: dns1764

i tried the plug and connections by the rear brake pedal. it still cuts out at half throttle. it almost shuts off once i go past half, not sputtering like full throttle in reverse. i have no clue what it could be

Posted by: sd1

only reason it sputters at full throttle in reverse is because of the reverse rev limiter....it still sounds like a fuel issue to me...what color was the plug when u took it out?

Posted by: dns1764

it was black. i think the plug went. i havnt had a chance to put a new one in yet. by the way what type of plug wrench do you use. i had a hell of a time getting mine off

Posted by: sd1

well if it was black your running way to rich.....you really need to clean and dial in your carb.......for the plug its a standard 5/8 plug socket with a 3/8" drive ratchet or swivel with ratchet....you think that plug is hard...try taking a plug off a ltr450 or kfx450....just take your time on this...clean your air filter big time and reoil and remove the carb and clean and recheck all the settings on it...if you dont have a manual their is a thread in this forum where someone was nice enough to link a manual for free

Posted by: dns1764

i rejetted it after i figured it was running rich. i think the plug was still black from when i had the 128 in there. i figure the plug went while i was riding. i'll give the quad a full tune up when i get a day off. thanks for all the help

Posted by: Austin81

make sure your choke is completely off too

Posted by: dns1764

that was the first thing i checked. i learned from a bad experience. i shut the choke off my brothers 400ex after it was warmed up. he thought it was still on and turned it to the on position. after riding for about 15 minutes he started adjusting the carb and screwed up all the settings.