I have an 85 ATC250R and it has recently been rebuilt. I rode it for a while and it fouled out almost instantly, I dropped the jetting down 2 sizes to a 135 and it fouled out after about a half gallon of gas (32:1 mix). Should I try a smaller jet (I dont have a set, i have to buy them individually) or could that lean it out to much? Where are the needles and float supposed to be set?

I havent had the jetting right in this piece since I got it. I enjoy the 10 minutes of riding I get at a time, the thing absolutely flys; Im just wanting a bit more than 10 minutes at a time without swapping 3 dollar a pop plugs.

 

try 50:1 dealer recommended.

 

Oh, Ive always thought 50:1 was absolute minimum. Im runnin cheap oil should that make a difference? I have synthetic AC oil but I dont really wanna use it in this thing cuz its 30 bucks a gallon.

 

Yes keep going with a smaller. A smaller pilot jet should help because the hondas come stock with the jets too big. It wont hurt a thing for you to keep going smaller on the jets.

 

UUUH It wont hurt a thing going smaller on the jets??? how bout a blown piston?? jeezus.. Does it seem to "load" up on the low end? Maybee check where you Needle and Clip is set at, and your piolit, also check your air-screew, its probobly not your main jet.

 

It wont hurt if hes only dropping down a size at time he can still go down a couple sizes without worrying about blowing up there dude.

 

yea, but fouling plugs usually isnt because of a wrong size main jet, and he said it runs fine, so i would say its the piolit jet.. OR wrong Gapped sparkplug, or wrong heat range.

 

Try replacing the needle jet set. The jet needle, and the needle jet may be worn, you can't see it, unless you have a new needle next to the old one looking at them with a magnifying glass. Same way with the needle jet.
Like I say, replace them both, don't just pull out your throttle slide and drop a new needle in expecting the problem to be solved. Remove the main jet and replace the needle jet also.
Sounds to me like this is what is happening, with both components worn, it is way out of calibration from 1/8 to 7/8 throttle opening causing the plug to foul.

I believe factory jetting was a 150 main jet and a 48 pilot jet, just for reference

----- Gimpster -----

 

Thats what i said was pilot jet you should read what I type before tellin g me im wrong

 

on the tank of our 83 act250r the sticker says 20:1 mix
i pulled it out today to ride it and i LOVE that freakin bike!!!!!!