Need to make adjustment to a/f ...running to lean...anyway the screw Im thinking is the a/f screw (in front of bowl) is not a standard common screw, not sure what it is looks like a crescent shape head. Does anybody have experience with this. I would really appreciate the help...sons dying to ride.

 

You said it is "running to lean". The a/f screw is kind of just a fine tuning of the slow (idle/pilot) jet. This will only affect up to 1/4 throtle, so if it is lean in the middle and on top, it will not help much there.

Some nice carb theory: http://www.dansmc.com/carbs2.htm


I have not had to adjust mine on the 250, but usually you would trun the screw in until it begins to run bad, then turn it out (counting your number of turns) until it again begins to run bad. Turn it back in half the number of turns you counted (you are just splitting the difference).

Best to have a service manual on hand, any time you mess with suff like this!

 

i went to the dealer and got one for an 04 or if you can get the stock one out cut a grove in it with a dremal.

use a peace of vacum hole to get it out.

the biggest thing i found with rejetting the 250ex is the needle jet you need to shim it.

after all the money i spent getting everything i needed i should have gotten a dynojet kit it comes with the tool and adjustable needle.

i also put a sparks pipe and K&n filter on it .......total waste of money...didnt see any advantage......and my daughter complained it was to load

also has an AMR revbox and will start in any gear but the backup light is always on

 

Another good read: http://www.thumperfaq.com/mxa_thumper_fuel_screw.htm


I guess we should be calling it a "fuel" screw on the 250.

 

Your are totally correct on "fuel screw" adjusting slow jet...I left out that it does not want to idle, regardless of chock setting. I was thinking before I pulled out the carb to clean, that It might just need a little more fuel in the idle circuit (turn out the fuel screw). Still not sure how to deal with this non common type screw head ?. Thanks for helping !

 

I just read from an entry on thumpertalk that the screw is a D head. The tool is 120$ at the dealer..no thanks. Any advice would be appreciated. Later

 

If it was previously running fine then began not idling properly, you most likely have a clogged up slow jet!

Lots of post about problems like this lately........