Pilot Jet

Im installing a JD jet kit and noticed I had a #45 pilot jet in there. Is this normal?

Kinda helps if I know what bike you ride, but the factory jetting on my '07 at least calls for a 42. A 45 is used in low altitude, cold temperatures.

I live in Hawaii, low alt, 70-90 degrees. I have stage 1 cams and a high comp piston. 2007 crf250r


Just got the JD jet kit:


red needle clip 5th

185 main jet


 I haven't had a chance to ride it hard yet, it takes a bit to start but seems to kick easy once its warm 

Get yourself a 42 and ditch the 45.


Do you have the manual with your JD kit? It'll tell you what main jet and needle clip position to use. Your piston won't affect the air/fuel ratio nor will the cam, so do as the manual says. If you don't have the manual, I have one and can go look for you. Shooting from the hip here, but I'm pretty sure you'll need that 185 and the clip in position number 4.


How many turns out is your fuel screw? Should be about 2 1/4 out from seated.

Edited by trozei

JD instructions say red needle, 5th clip 185 main jet. I just ordered the #42 pilot, thanks for the tip

Edited by sloc88

Try that and let me know how it feel. Don't forget to read your spark plug afterwards to see if you're rich or lean. If so, adjust, ride, and check the plug again. Repeat as necessary.

Try that and let me know how it feel. Don't forget to read your spark plug afterwards to see if you're rich or lean. If so, adjust, ride, and check the plug again. Repeat as necessary.

Thanks for the tip. Put in the 42 and she fired up second kick. After I adjusted the fuel screw. She fires up first kick! Dialing in the carb is a PITA. Time to go ride... 

Well I just got back from my ride and I have a hell of a time starting the bike mostly after a fall but sometimes just after killing it and keeping the bike upright. When its idling the bike runs at 1700 rpms(going by the tach) but once i have to kick it feels like it wants to turn over but its doesnt go. Sometimes, right when it feels like its going to turn over, I give it a blip on the throttle and it will start. Almost feels like its not getting enough gas when starting. This is super frustrating because like I said earlier, the bike was doing well around my house but seems to do worse when its super hot. Any tips for me?

Finally got around to putting the clip in the 4th position and dropping to a 180 Main. Still hard to start cold but kicking over first kick once warm at my house. We'll see how she does on the trails tomorrow

Rule out valve problems by checking your valve clearances, then if ok start dialing in the slow speed circuit.  You say that it is hard to start when 'super hot', are you using the hot start?  You want to get the bike up to operating temperatures and then start adjustments on the fuel screw.  Start by turning it out to richen it up.  As you turn it out the idle should increase and you should turn down the idle screw to compensate.  Use small increments - 1/8 to 1/4 turns.  Blip the throttle after each adjustment and if it hesitates coming off zero throttle turn the fuel screw in, 1/8 turn increments, until it doesn't.


After adjustment the bike should start relatively easily when cold, using the choke.  When hot, you should have to use the hot start.  If none of these adjustments work re-install the 45 pilot jet and re-adjust.



Bike Started and ran great, I think im getting really close. My issue now is that the bike hesitates hard at Wide Open Throttle for 1 second, then accelerates. Its almost like a bog. Should I go bigger or smaller on the Main Jet?

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