After market air filter causing idle issues on atv

[kartkid11]

Ive hade this 90cc 4 stroke chinese quad for a long time. It sat for a couple years and mice decided the wiring looked like a nice snack, so my grandfather rigged something up, it then sat for another 3-4 years. Fast forward to a couple months ago, i decided to pull her out again and see if i could bring'er back to life. After rigging up some wiring I came to the conclusion that the carb was dirty, opened it up and it was pretty much past its due date, so i ordered one off ebay for $10. Now lets fast forward to today, installed everything and it definitely was the issue, but i cant get it too idle without the choke on, it will rev just fine with the choke off, doesnt bog out or anything, just wont idle. I spent a good 2 hours messing with the idle and fuel mixture screws and got it close with the fuel screw all the way in, but just cant seem to get it to stop dying on me. The carb came with a k&n style cone filter to replace the old air box, so what im thinking is they didnt upgrade the jets to accommodate the amount of air thats now being sucked in and the engine just cant get enough fuel from the fuel adjuster screw alone. Anyways id appreciate some help, thanks!

- Summit

 

[KartFab]

My best guess is tgst you had leftover varnish/fuel junk in the tank and without an inline fuel filter you just clogged up your carb.

Classic lean condition caused by fuel delivery problems. Also, check to see if you have an idle pilot jet. If so, you would need to clean it.

Here's this link. May be helpful
http://www.iwt.com.au/mikunicarb.htm

 

[kartkid11]

My best guess is tgst you had leftover varnish/fuel junk in the tank and without an inline fuel filter you just clogged up your carb.

I was afraid of that. Well guess the carbs commin off again. Thanns for the help

 

[Hellion]

Agreed on the possible, most likeliest causes.

Don't forget that by its very addition, a less restrictive air filter is going to make the engine run leaner than before on account of all this extra air rushing in.