New member seeking help

[Noti95]

 

 

Hi everyone i am coming from Europe and looking forward to join this community. I'm currently riding Kymco mxu300r which is the same bike as Brute Force 300 just different plastics.

Recently i came to a problem with this atv when accelerating near full throttle it suddenly lost power like i quickly released throttle but i kept throttle lever in the same spot. Since then it pulls off fine until you are past first 1/4 of throttle and then starts stuttering/misfiring. Same behavior when revving in neutral or riding. Cleaned and gapped spark plug but no better.

Could this sudden symptoms be from bad ignition coil and cdi or dirty carb? Carb was never cleaned before but i used stabil in gas when atv was not in use. Atv has 1000 miles carb on it is Keihin cvk32.

Sorry for longer post and thank you in advance.

Edited October 20, 2024 by Noti95
Added video of the problem

[Gwbarm]

I would start with the carb and see if it helps. Are you using ethynol fuel in the carb? If so it can form a jelly like substance in the float bowl when not used for long periods of time. Did you check you have good fuel flow to the carb, there could also be a problem with the petcock.

[Noti95]

The problem is you can't buy non ethanol here in eu, all gas fuels contain 5% etanol but i used stabilizer over winter when not using it regularly.  I'll start from checking the petcock and cleaning the carb. 

[Mech]

Yup, check the fuel flow from the tank, then at the drain screw on the carb. If that's ok then take the carb out and strip it entirely, clean it carefully, and it will probably come right. I doubt it is going to be spark, and if it is it's going to be tricky to diagnose. The fuel system is easier to work on, but you have to be thorough and when the carb goes back on you have to know it's right/clean. Otherwise, if you don't know it's all real clean, and been blown through every jet and drilling, you are going to be back to guessing whether it's fuel or electric..  Make certain the fuel system is operating first.

[Gwbarm]

Well, your gas is a little better than ours here in the states, it is 10% ethynol, but non ethynol gas is available but its about 1.00 per gallon more. I would do what you are doing if non ethynol was not available.

[Noti95]

After carb cleaning atv works like new.

There was no visible gunk or contaminants but cleaning with carb cleaner and blowing all jets with compressed air obviously did the trick. 

Thanks for your help with troubleshooting.

[Mech]

Good work. Thanks for the feed back.