Maintenance & Technical > KX500 Original
Motor surging issues!! Help!!
Mick:
Oh I've had them WFOT for +700ft on occasion :-D No issues and I can tell you with certainty the carb isn't the limiting factor here. I agree with the logic of those members on the atv site, but I disagree with the cause. I disagree with them because a carb?s size isn't an indication to how large the float bowl is. The 44mm carb's bowl isn't (if any) much larger than your 40. These carburetor manufacturers don't machine all new components for each carb. They all share essentially the same pieces, but the throat or bore of the carbs are obviously machined larger/smaller for each desired application. However, I do see where they are coming from(?) If your float is too low, then you're motor is using the fuel quicker than the gravity fed carb can replenish it. When the fuel gets too low, the air passing through the bore has a difficult time picking it up causing a lean condition. I've seen this happen many times to ill jetted machines. I will say though that typically under these conditions the motor will lean out severely under power, and not when you close the throttle. So that essentially is running the bowl dry, but not because it's too small. The carb just needs tuned correctly.
ID KX500:
--- Quote from: KX5Zuki on May 26, 2009, 03:18:08 AM ---What about running the bowl dry? I am a member over at atvdragracers.com and there saying, with my 700ft full throttle run, the 500 can suck that "small" 40mm carb dry in no time, which would explain the surging, as its starving for fuel, and even hanging up a lil. I am still going to do a leak down test on the motor, but in the mean time I am going to be looking for a 44mm carb to deal with the long full throttle run. And also run dual fuel lines to the carb. Anybody else run there 500 full throttle that long? This is mostly a drag bike.
--- End quote ---
That sounds like you're on the right track I get surging when I leave the gas off,,, so maybe check fuel flow and ventilation from your gas tank,,, to be sure enough gas even gets to the carb.
KX5Zuki:
Hmm, well, you are probably right. I need to find out how and to what specs I need to set my carb up to. If anyone has a site on the set up of the Mikuni carbs please share. I will also check the pintle valve in the tank, and the vent up top. It might be a while until I am able to tell for sure. Dont have easy access to the quad whenever. Thanks for the help, and I hope I can get this thing set up. Banshee Eater! HaHa
cbxracer30:
I would like to start off with a little bitch, would like to see you put some rear fenders on that machine . I watched a guy with a honda 250 get out of control , run over his foot then his leg got sucked into the rear sprocket , that dug about to inches into the meat on the back of his thigh. The only good out of it all was his helicopter ride he didn't get to enjoy. Ok then if you decide to go with a 44tron make sure it has an alcohol float valve because the stock valve is only good for 300ft WOT. A mikuni 3.5 works well when tapped to fit.CBX
Polar-Bus:
cracked/dry rotted intake boot?
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