wr250f hesitation

ive recently baught an 05 wr50f and the bike doesnt seem to be running correctly.

im not sure which jets are which but i wrote down the sizes when i was cleaning the carb out.




the engine is stock but it has an aftermarket exhaust. ive been told its a yz exhaust but im not sure so here it is for you to decide...


im from the uk and ride between 0-500ft and the temp here is pretty cold at the moment 0-15 degrees.

ive set the fuel screw at 1.5 turns out and smoothed the idle out with the idle screw. it starts and ticks over fine but if you rev it fast it will bog down, also in the low rev range the bike is jerky to ride, kind of like a missfire in a car.

ive also noticed the bike sometimes holds the revs up when you ome to a stop and it will slowly come bak down to idle.

its pretty obvious something is wrong and ive only got the bike mot'd yesterday so ive only ridden the bike about 10 miles. im going to pik up an adjustable fuel screw tomorow as its taking ages to rotate the carb to alter the fuel screw at the moment.

im very new to all this, this is my first proper offroader and my first 4stroke.

any adice is greatly appreciated.


I have a White Brothers pipe, opened air box, gray wire disconnected, and the o'ring trick also. But i still have the bog. I have not re-jetted anything yet. I feel the jetting is the problem. I was riding in some thick mud the other day, and bike almost didn't bog at all with the choke pulled out when up to temp. Seems like it needs more fuel. What are the trick numbers?

Did you check the AP timing? Did you check the leak jet (what size is in it), condition of the AP diaphragm?

You probably ought to pony up for a James Dean jet kit, a Merge Racing fuel screw and a 50 leak jet (James Dean can supply it in the kit if you ask nice).

can anyone tell me what exhaust i have on my wr from the pictures above?

i purchased an adjustable fuel screw this morning and ive managed to smooth the bike out alot better, although not perfect. ive had totake the fuel srew out about 2 5/8.

does this sound ok or am i going to need to change any jets in the carb?

thank you


No, 2-5/8's is in the range of acceptability.

thanks for that.

does anyone know what exhaust i have on my wr as i havent a clue what its from.



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