Hey Hotrod. I don't know much about the 500s, but I posted a similar issue with my 650 v2. All was great until 30 mph in high gear. Then, like you said, totally flat. My issue was the CDI. Replaced it with a dynatek today and it's running like a champ now. Hope this helps.
I soaked the carb in chem dip 3 days blew it all out and reinstalled it and it’s still doing the same this after 1/4 throttle it goes to cutting out and popping and sputtering . Iv tried adjusting the idle air in and out and to the specs per the Manuel . Nothing make a difference. I’m wondering now if the coil is braking down at high rpms of if the CDI box is going bad
So does this happen right away after start up or does it happen once the atv gets hot ... If it's cutting out right away don't give up on the carb buy a rebuild kit there very cheap do you have a dyno jet kit or stock ? .
Does the atv pick up again after 1/4 or does it just keep cutting out ?
There's so many things it could be
Bad spark plug
Incorrect settings on the pm screw
Clogged pilot jet use a tiny peice of wire to clean that one out all the little holes and the main hole is so small any debris can clog it
Check all your vent lines isent clogged with mud
Air box / snorkle not restricted
Does your year have auto choke or manual ? Mine has auto choke I hate it I had to unplug it cuz it was broken and it kept flooding my quad
My advice is to stick with the carb for now until there's nothing left to do with it rebuild it and if after your 100% sure it's not the issue then move on to test coil and stator you can't test CDI unless u swap it out I'm not sure if you can test a voltage regulator or not but make sure the carb is 100%
Sorry about the lengthy reply I just understand how frustrating this problem can be this is the list I went over as well I did end up replacing my coil and rebuilding carb So I'm not 100 percent sure what actually fixed it but it was deff the carb rebuild and or coil you could replace it just to see but I'm leaning toward carb
I have put a kit in it from all balls racing and cleaned all the internals in the carb. Has a new spark plug Iv drained and cleaned the fuel tank and put good fresh gas in it. It has the factory air box and air filter the intake tube has been checked and is good and tight. It has a manual choke it’s not sticking and is working like it should. It will do this from start up and when warmed up . And from 1/4 on it just keeps cutting out .i have noticed that in nutral you can rev it past 3/4 throttle and it won’t cut out but in gear 1/4 throttle is as far as it will go before cutting out .Thank you for your reply !! I’ll take any help I can get lol.
You can't interchange the pilot jet so, that's out.
You can swap the other 2 and it will do as described .... basically crap out when you hit the throttle.
Easiest way to make sure you are good is:
Biggest jet - it is the main jet, goes below needle.
Pilot jet - only fits in one place.
Medium jet (aka starter jet) - well, there is only one other location.
If the starter jet is installed as the main jet, the quad will simply starve for fuel the moment you hit the throttle. Should idle fine forever though.
If it idles fine and craps out on throttle - high likely that it is a lean condition.
As already pointed out, check for dry rot cracks in manifold, boots, vacuum hoses.
Be sure vacuum hose is connected so that the slide needle moves. When I clean any carb, I will blow in and out (with my mouth) through the vacuum port to make sure needle moves up and down.
Make sure your airbox is connected, with filter in place, cover on, intake tube, etc. The airbox provides proper air pressure resistance. Try to run without it, and all will be super lean.
One last thing. Unsure what Cat used for carbs in 2002 but, worth taking a look. I had this happen with a buddy's 2003ish Suzuki Eiger. It was breaking up badly on throttle after 15 seconds or so. We thought is was a CDI problem.
The carb had an internal filter under the needle and seat.
I pulled the carb, float, needle.
There is a small set screw on the seat. Removed that and GENTLY twisted back and forth and pulled the seat out. Found 3 small brass filter screens all boogered up.
This meant that gas would fill the bowl easily during idle but, when you open the throttle and suck all the fuel from the bowl, it wouldn't refill quick enough.
Let off the throttle, bowl would fill and throttle would be great for another 10 seconds.
If you think you may damage the seat during removal, just clean the heck out of the intake path - BOTH DIRECTIONS. Shoot generous amounts of carb clean in both directions - fuel inlet and back from the seat. Generous amounts of air as well.
Ya I'm sorry to say I'm out of ideas mine was doing this exact same thing as yours I completely rebuilt the carb and changed my coil and mine is fixed looks like it may not be that simple for you sorry I couldn't help
When I first got my 2001 AC 500, it did the same thing. Finally I removed the gas tank and dumped it out into a white 5 gallon bucket. Was surprised that so much crud came out. After a thorough cleaning and installing an inline filter, it never bothered again. I hesitated to post this, because I don't think it's your problem. 1 thing you might try= a few different size main jets, try a leaner size or 2 and a fatter one. That might help eliminate the carburetor and point to electrical side. Then when you nail it down, you can still fine tune the main jet size to give maximum top speed. That will be the right one. BTW, the previous owner of my 500 was so exasperated that he sold it to me for $400. I cleaned the tank, ran it for years then sold it for $2,500. Remember the book "Zen and the Art of Motorcycle Maintenance" ? When you figure it out......