[NvrDwn]

I've got a 300 fourtrax. I'm mechanically capable of doing about anything, but as the title says me and carbs don't know each other very well.

I have taken the carb apart and cleaned it. Not very well I guess, as there is some varnish but all the passage ways are clear and I got a carb rebuild kit. Everything seems to install one way with the exception of two pieces. The idle mixture screw (I understand this) and the needle. What does this needle do, and how does positioning it differently change the power?

I'm also thinking of changing the exhaust and modifying the intake for better flow. I've read that this should be rejetted, but not one thread I've found has given an exact answer. I'm not even sure how to tell if I'm running lean or rich. I'm used to plugging in a "programmer" and knowing so please excuse my ignorance.. I'll take a shot in the dark and say I'd need a 128 and keep the stock 40?

While I'm here another question.. The atv seems to stumble or sputter during partial throttle. What could cause this?

Yes I've searched. I've lurked around a lot recently. ?

 

[NvrDwn]

Thanks. Yes that needle. I replaced it when I got the rebuild kit and it was / still is in the middle. So if I raise or lower it maybe my part throttle will be fixed? I'm right at 1k elevation. Where I'm taking it at the end of the month will be up to or higher than 2k elevation. Should I raise or lower it? Thanks for the help.