I have 2006 Honda 250ex that is having carb issues, and it has had me chasing "gremlins" for the last week. Everything was running fine till I adjusted the valves and yes, they have been done correctly. After reassembly it was running lean so I cleaned out the carb to no avail. I've now gone through the carb two more times and everything is clean. It currently is running so rich at idle (with the idle screw turned to the lowest idle setting) that almost any amount of choke kills the motor even when cold, and it runs so lean as you rev it up that the motor won't exceed 4500 rpm (CDI limits it at 7500 rpm). Once moving if the choke is applied it runs almost as normal, but it still has a little hesitation and won't quite hit the limiter. As far as I can tell there are no air leaks in the intake system. The atv does have a preformance exhaust system, better ignition coil, and a modified air intake. Is this a sign that I need to re-jet the carb or is it more serious and am I going to need a new carb? I am at a loss on what is wrong, and I would greatly appreciate it if anyone can give me some advice.

 

Needing choke to run is a sign of lean, not rich. It sounds like it is not pulling gas from the tank. Have you checked the gas line and the screen filter in the tank? How about the gas cap itself? The cap needs to breathe from the hose. Loosten the cap and see if it runs.

 

I've check the lines, cap, and screen fliter. They are clear. I kinda thought that at first, but if that were the case, then I'd figure that if I let it sit and idle, letting the carb bowl fill with gas, then it should run fine when floored till it emptied the bowl. The gas in the bowl will get the atv an 1/8 of a mile.