Hey everyone have 400ex that has bad idle, played with the idle adjustment turn the idle up a lil
bit too keep it running but it's just dies after min or 2 of runing or if I rev it and let it the Rpms go back down it dies.


I already cleaned the carb,check and did a value adjustment, spark plug, oil, oil filter, fresh prem gas.


Freind said i should up my main jet?


Please help guys I'm going to BUSCO BEACH in a week and half!!!!!!!!!!!!!!!!!!!!

Thanks!!!!!!!!

 

Also it's all stock!!!!

 

Check to make sure the fuel line has good flow coming out of it if you take it off the carb. Then, make sure the carb is very clean. It doesnt take much to cause one to run bad. A glowing headpipe is a lean condition. If you are sure the carb is good and clean, then I would start adjusting the pilot screw out maybe a turn at a time until it is running much better, then fine tune once it is close. Does it rev ok, but just idle bad? If it revs pretty good, then the main jet should be fine.

 

Yes,it runs and revs fine it just dies out. The pilot screw you are talking about Is under the carb a flat head screw?

 

How old is the unit? This is a recent development? You may be able to go up on the pilot, but if it has run well in the past I question what may have changed. Possibly you have a small air leak.

 

In unit you mean how old is the atv? It's 1999 and yeah it started this season. The bike did sit over winter, but when I got it out for this season it wouldn't even start thought it was a plug change it with new gas, still wouldn't start we cleaned the carb it started but now I'm stuck here where it just idle for a min and dies

 

And also along with the other prosedures I listed before.

 

I would start by checking for any small air leaks on the carb. The best way i have found to do this is take a can of starting fluid while its running and lightly spray the carb and boots.

 

Thank you for the options guys!!!! I'm going to clean the carb really good and do the air leak test will update on how it goes and how it runs.

 

What do you mean very clean carb? did you disassemble carb an vat it out an then reassemble? If you did that then should be fine. if atv run good last season an you have added any new add ons then mixture and carb setting should be fine..carb setting or jetting doesn't change just by sitting up..Need more imformation thanks just trying to help understand whats going on.