My new to me 250r (250r jetting question)

[wcr400ex]

I bought an 86 250r today

It is bored to a 265, i run 40:1 racegas/oil it has the stock carb paul turner racing pipe and reeds. I put a new plug in and a new Kand N. I am running no lair box lid

I am at a 170 and it sputters at wot.

I am 1.5 out on the fuel mix screw

Middle clip on the needle

Any help or suggestions would be extremely helpful

Thank you
Josh

[velocityatv]

My suggestion.......get ride of the 18 year old carb and get a kiehin air striker. You would definitly notice a lot more performance out of it. Did you check your reeds? Sometimes a weak reed can cause people to think it's the carb. I run a 265 with a 38mm a/s and LRD adjustable pipe w/ K&N and I run a 172 main. Damn, that 170 on a stocker sounds big.

To some what accuratly find your main jet size, your supposed to go up in size until it starts to sputter or even backfire at wot. Then take it back down until it quits, what ever size you end up with should be correct. It probly wouldn't hurt to try and go down a size or two if you notice on plug runs that your running fat.

Also if you just bought it check and see what plug they had in it. And remember always stay with a 8 heat range never go hotter. most people use a BR8ES (RESISTOR)
B8ES (NON-RESISTOR)
B8EV (V-POWER I BEILEVE)

[QuadRacer041]

i agree 170 sounds way to fat, especially if you have a sputter up top. what kind of compression you got?
if its below 200 there is really no need for race gas.
reeds really only affect performance at the botton or off idle accelartion. i would also say maybe gfo with a bigger carb maybe not a 38mm thats pretty big but a 35 or even a 36mm, just make sure you get a PWK model.
i put a pwk 36 on my woods bike and noticed a differnance all through the board especially throttle responce.

[wcr400ex]

I am running an 8 plug, i ll give a 160-165 a shot thanks for the input.

[wcr400ex]

I put in a 160 it seems a lot better but the axle bearings seized up before i could really tell.


Thanks again!
josh

[Blown 331]

I'm in the same boat. When you say to run a 160 or 165 is that with or with out an air box lid?

I have a stock '85 ATC250R. Stock carb, stock piston. It has a DG pipe and I'm trying to jet for no air box lid. It had a 130 and I'm up to a 150 right now. The best I've got it to run was a 142 with the air box lid on. I don't have any jets between 150 and 180. Should I try buying a 160 or somewhere around there? I'm pretty good jetting 4-strokes but I can't really tell if I'm lean or rich.