help me out jetting this 07 crf250

shimming my valves so i thought id check my jetting

main 178

pilot 48

leak jet 70

slow jet 68

not sure on the needle yet didnt check that.

only mods are powerbomb header and white brothers pipe

the bike runs good but does bog down low if i dont keep the rpms up and just hammer it it will die. hot starts can be a pain sometimes

elevation is 900 ft

what are the stock jet sizes? temps right now are in the 80s and 70s

Should be a 42 pilot, 172 main and a 45 leak jet to get rid of the bog. The plug should be close to black when you pull it out the way the jetting is set up. In NE Ohio, I set them all up like this unless the head is ported, then I'll run a 38 or 40 pilot jet. Start with this jetting benchmark. I'm sure it will run a lot better.

While we're on the subject, I pulled apart my newly acquired 06 CRF250 to check the jetting too.

Pilot 42

Main 175

Leak 70

Didn't check anything else. I'm running stock piston/ HC stage 2, and dual Yosh exhaust. Mine is kind of a pain to hot start too. I'm just south of Cincinnati a bit. I plan on ordering a new leak jet, but should I get a 172 main, or will it make much difference?

ok thanks alot ill get those jets ordered and on the way. are you still running the stock needle?

ive been looking for a 45 leak on the parts finders and cant find one anywhere. where do you order it?

ok thanks alot ill get those jets ordered and on the way. are you still running the stock needle?

Yes the stock needle in the 4th position. I've had better luck getting leak jets from a Yamaha dealership.

While we're on the subject, I pulled apart my newly acquired 06 CRF250 to check the jetting too.

Pilot 42

Main 175

Leak 70

Didn't check anything else. I'm running stock piston/ HC stage 2, and dual Yosh exhaust. Mine is kind of a pain to hot start too. I'm just south of Cincinnati a bit. I plan on ordering a new leak jet, but should I get a 172 main, or will it make much difference?

The way the weather is right now, the 172 may help a little. I'm in Lexington right now and it's pretty hot.

Thanks, I'll try a 172. It is pretty hot today. What kind of jets do you guys run during the winter?

Thanks, I'll try a 172. It is pretty hot today. What kind of jets do you guys run during the winter?

Usually bump the pilot to a 45 and move the needle clip down 1 notch. Unless it's below 45 degrees, you can leave the main jet alone. 175 any colder than that. Of course, adjust the air/fuel mixture screw before changing the jetting around.

installed a 172 main 42 pilot and moved the needle to the fourth position from the top. still waiting on the 45 leak so im still running the 70. now the bike bogs BAD twisting the throttle. it will almost die every time. and the fuel screw has no effect at all on it. any ideas?

smaller leak get the 45~!

Try a 45 pilot jet. I use a 45 pilot and a 172 main in my 09. Head is ported. I tried a 42 pilot in mine and could not get it to start. Runs great with the 45. Im also running a 70 leak. Haven't had a chance to try a smaller leak jet. Mine doesnt seem to bog. Also running an NCYS needle with the clip 3 down from the top.

my 08 likes the 45 pilot 1 turn summer, 1 1/2 in winter, 172 main, stock needle and clip, 45 leak ( this does wonders for the bog), mine will also stutter with a 42 pilot, lots of starting issues with the 42 pilot

Have you checked your acc. pump diaphram? It could be in bad shape, and not drawing in enough fuel when you crack the throttle quickly.

im having trouble with the accel pump leaking fuel now. could it be bad? with the 42 pilot in the bike it starts wonderfully, just bogs. until i get the 45 leak its hard to say what its actually doing. i should also note the bike has a high comp CP piston

You have a damaged AP diaphragm. Time for a new one. Easy job, carb on bike. Ethanol fuel ruins them

Try a 45 pilot jet. I use a 45 pilot and a 172 main in my 09. Head is ported. I tried a 42 pilot in mine and could not get it to start. Runs great with the 45. Im also running a 70 leak. Haven't had a chance to try a smaller leak jet. Mine doesnt seem to bog. Also running an NCYS needle with the clip 3 down from the top.

Keith,

I can't believe you're running that big of a pilot. My kids 08 has a serious porting job and I was running a 38 in the summer when it was 80+ and a 40 when it was under 80. Winter was a 42 for unheated indoor tracks and it was on the verge of running a little flat. Air/fuel screw almost all the way in. With a ported head, the jetting should go down. (Should) With the 45, it may make it easier to start, but it can't possibly run nearly as strong on the bottom with that big of a pilot. Of course, there are many varibles that may dictate that type of jetting, but it's strange going that big with a ported head.

Keith,

I can't believe you're running that big of a pilot. My kids 08 has a serious porting job and I was running a 38 in the summer when it was 80+ and a 40 when it was under 80. Winter was a 42 for unheated indoor tracks and it was on the verge of running a little flat. Air/fuel screw almost all the way in. With a ported head, the jetting should go down. (Should) With the 45, it may make it easier to start, but it can't possibly run nearly as strong on the bottom with that big of a pilot. Of course, there are many varibles that may dictate that type of jetting, but it's strange going that big with a ported head.

I think I may need to take what I said back. I rode last night and the bike was bogging a little and just seemed sluggish. I tried my 42 earlier in the spring and it didnt want to start or run worth a crap. Seemed way too lean. Its starting to get hotter here. I turned the fuel screw in to about 1.25 open and it got a little better but not that good. will try the 42 again next time out and play with the fuel screw. Hopefully it will relieve the sluggishness. It was driving me crazy. Couldnt ride worth a damn. Im also going to try a 45 leak.

I think I may need to take what I said back. I rode last night and the bike was bogging a little and just seemed sluggish. I tried my 42 earlier in the spring and it didnt want to start or run worth a crap. Seemed way too lean. Its starting to get hotter here. I turned the fuel screw in to about 1.25 open and it got a little better but not that good. will try the 42 again next time out and play with the fuel screw. Hopefully it will relieve the sluggishness. It was driving me crazy. Couldnt ride worth a damn. Im also going to try a 45 leak.

The 45 leak jet does wonders. I think you'll be happy with it. If it still boggs, something is wrong. Are you dealing with a hard landing bog also?

The 45 leak jet does wonders. I think you'll be happy with it. If it still boggs, something is wrong. Are you dealing with a hard landing bog also?

I've got a 50 leak jet ordered. Hope that will be close enough. Cant really say about the hard landing bog. I don't ride aggressive enough at this point to really experience rough landings. If I do I probably wont be riding away from it anyways. lol My other problem is the previous owner took the plate out of the carb bowl that covers the leak jet. Do you think this is going to be a problem?

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