I have a 2004 Arctic Cat 300 ATV 4x4. Recently, it lost of significant amount of power. Started and ran fine, but just did not have high end torque like it used to. Engine did not cut out or sputter, just little high end power. Revved ok in neutral. I checked compression and it is well within spec (175 PSI with throttle wide open). So I decided to clean the carburetor. Removed all jets and such, sprayed with carb cleaner and blew out with compressed air. Put it back together and reinstalled. Now engine starts fine and idles great, but as soon as I start to open the throttle the slightest bit, it dies. I've tried adjusting pilot screw all the way from about 1.5 turns to 3 turns and no change. Took it back apart. Tiny washer and rubber o-ring at base of pilot screw went missing. I must have blown them out and did not see them. So I bought a kit and installed new ones. Still the same problem. Jets all seem open. I can see daylight through each of them. Still starts fine and idles fine, but just won't let me open the throttle the slightest bit without dying. I am out of ideas on what to look for. Any help will be greatly appreciated.

 

Carb system - Float level?

If you can, push (or jack) ATV's front wheels on a 6" high block and try reving engine again. Then, push (jack) ATV's rear wheels on a 6" high block and rev engine again. If change in engine behaviour when engine is tilted, then its probably from float level setting.

Hope this helps....

 

I know this is an old thread, but did you ever resolve the issue? I am having a very similar problem on my '03 300 4x4.

 

​​​​​​I'd check the jet sizes if you took out the old ones And didn't look at the sizes of the new ones it's possible you mixed them up especially if there unbranded .OEM will have the numbers on the top or side or the jets main will be biggest jet around #128 pilot will be around #35 if you have a secondary jet it's gonna be around#85.air mixture screw should be around 1 1/2 turns to two turns out if it idles fine but is bogging at 1/4; throttle.your pilot jet and probably the main jet is to small or mixed up I've actually done this to myself and it's aggravating trying to figure it out .hope this helps some also if it has a cv carburetor with slide with a diaphragm the diaphragm May have come apart and the slide won't lift with the engine vacuum.cv
carbs are bad for that .​