Just bought a T4 how should I adjust the air/fuel screw for the 250EX?

[TRFOXX]

Bought a T4 for son 250EX and its back firing a little, I did not rejet yet and I know that it would take care of the problem, but he was wanting to ride today and i wanted to see if I could adjust the air/fuel screw so many turns? It runs really well without even jetting, just has a slight backfire. Thought that messing with the air/fuel screw might make it a little better. Should I turn the screw in all the way and turn it out 2 1/2 turns or what? I know that a 1/2 turn is considered a whole turn. Stock air box lid on with stock filter, but if you guys have any advise for me I would greatly appreciate it!
Whats the stock setting of main jet and piloit jet? Ill probly go up a size on each. Thanks

[RUFIO]

Originally posted by TRFOXX
It runs really well without even jetting, just has a slight backfire.

The same thing happend when i put an E-series on my 250ex with a Twin Air & Open Box..It ran amazing and it felt like it gave it gains everywhere (Without Re-Jetting)..I just tightend the air screw up and opend it just under 2 turns and i never rejetted it which probly wast a good thing to do but it ran great so i left it alone. It back fired once in awhile as well.

[TRFOXX]

OK, the manual dosent show where the air/fuel mixture screw is.
Is it on the left side of the machine? Do you have to take off any plastic? I check the spark plug after riding it a bit going up and down the road and it was a little white. So that means that it needs more fuel right? I have the stock air box lid on with no holes in it. what should I do at this point? Sorry I havent messed with machine much until now, unlike my 400ex. a little help would be great!

[White_Knuckles]

The fuel screw is under the carb on the front or engine side of the float bowl pointing straight down. No need to remove plastic. You may reach it with a stubby driver at an angle. 1/2 turns = 1/2 turns, the 2 1/2 setting is for the idle circuit only and will help correct the let-off backfire, (mine is out almost three full turns).

The white plug may indicate a lean main jet condition. This needs to be addressed as ping or pre-ignition and excessive heat may damage Mr. Motor. The best combination is a Keihin (Honda dealer) main jet from 102 - 108 when a high flow filter (UNI / K&N) and airbox mods such as lid removed, 4-6 1" holes drilled in lid and, or the intake snorkle opened up from the size of a quarter to the full oval shape. More flow from the pipe means add more fuel (main jet). Increase the air flow to take advantage of the larger jets. Cheap mods and best use of the pipe.

If you leave the stock filter/airbox, re-jet the main to 98-100. In both cases adjust the fuel idle mixture out to 2 1/2-3 full turns.

[White_Knuckles]

Stock main on the 250EX is a 95 the Pilot is a 38. No need to raise the Pilot only the main. Leave the stock needle clip setting. The White Bros. disc system is way different than the straight through style T-4 so go with Pro Circuit's recommended jetting I posted above. A larger pilot (40) will drown it, trust me the stock is fine.

Look at the 1" UNI pop-in filters that insert into the airbox lid. They cost $5.00 for 6 and work great!