Crf 250 jetting

[Ron Hamp]

I just did some more testing on the dyno this is what i have for jets on the stock 08 crf 250 with pump fuel 172 main jet 45 pilot jet #40 leak jet the needle set 1 step richer than stock make sure you readjust the idle mixture screw and you may have to adjust the pump actuator screw under the cable cover . the bike now makes over 1 hp more for a 3000 rpm spread it went from 19.1-19.4 pounds of torque and from 34.9- 36 hp you will still nned to test @ the track to see if it works better .

[Honda_250f_rider]

cool, thanks... So for 2100 feet do you still recommend a 168 main and a 42 pilot? And how about the needle position?

[mototoad]

RHC,

If one of your customers try's your jetting and they swear by it please post and update. I'm a michigan rider and would be happy to have you duplicate to my 2008. But I haven't ridden the bike yet.

Thanks

[See-Are-Ef-Too-Thir-T-Ef]

How does honda suck that bad?

[Ron Hamp]

i deliverd the bike back to the honda shop yesterday and the shop owner rode it in the parking lot and said it was considerably better than the new stock 08 they had sold the day before .it takes all the trottle quikly we will know more when its tested on a track off the hard jumps but i beleive its going to be good .

[rob450thumper]

i deliverd the bike back to the honda shop yesterday and the shop owner rode it in the parking lot and said it was considerably better than the new stock 08 they had sold the day before .it takes all the trottle quikly we will know more when its tested on a track off the hard jumps but i beleive its going to be good .

Ron did you do the same kind of test on a stock 07 model? If so what did you find works best?

[oabike]

Ron - I tried your jetting today just for kicks. I think the 172 main is spot on but the pilot and needle are way too rich. My track is at 1000' and it was about 72 deg today. I have also dyno'd the bike with stock jetting at sea level on a 60 deg evening. Your jetting ran ok up and down the street but I think that is more a result of the main jet. I had my best results on the track with a 42 pilot, 2 turns out on the fuel screw, needle on the 2nd clip down, 172 main. I'm still up in the air on the leak jet and pump screw as I still get a bog with a fast application of throttle. Since the leak jet is not practical to change at the track I may go with a "merge" or "r&d racing"adjustable jet. On the dyno the stock jetting ran very rich throughout the entire rpm range. I will test my jetting on the dyno in the next week or so and let you know how it works.

[Ron Hamp]

after richening the needle 1 notch i thought the pilot @ 45 might have been to much but like you said it ran great on flat ground .and thats why we have to check them @ the trackthank you

[455]

Even though you both were using pump fuel, (I assume), the blends differ across the Country. Pump fuel changes season to season and in high population areas for polution control. Not to mention all the different brands/blends on the market. Thats why I always use race fuel and buy it in 5 gallon pails from VP. Jetting is hard enough work, not to have the difference in pump fuel blends messing it all up.

[Jimbo45]

Any track tests with your jetting yet, Ron?

[Honda_250f_rider]

I used a 168 MJ with a 45LJ, and it seems to be working good for me at 2100ft.

Pulled the sparkplug to check, and the end of the electrode looks brand new and the metal thing above it has a very light tan color, so I think I'm right on the money... 4.5 hrs on bike.

[Jimbo45]

I used a 168 MJ with a 45LJ, and it seems to be working good for me at 2100ft.

Pulled the sparkplug to check, and the end of the electrode looks brand new and the metal thing above it has a very light tan color, so I think I'm right on the money... 4.5 hrs on bike.

Great! Stock needle? What clip position?

With my '08, I think I need to be on the fatter side, at lower throttle settings, nearer to what Ron has going. It is cold here for now (30-45 degrees) and I'm at 875 feet. Mine is definitely not rich with stock jetting, on the low end, anyway, in this weather.

I have a collection of main and pilot jets on hand, and am going to order some leak jets tonight. I think I will start with a 172-175 MJ, 45 PJ, stock Needle on 3-4th clip, and a 45 LJ (at least until Santa brings my JD jetting kit).

Ron, what conditions/elevation did you perform your dyno tests to come up with that? Indoors I take it? Any chance to track test that jetting yet?

[Honda_250f_rider]

All I changed was, putting in the 168 main jet, installing a 45 leak jet, and a zip ty fuel screw... It has the stock pilot jet, needle, and needle position...

The 4.5 hrs (on the meter), was from the 3 rides I could do before the snow came here ... And the temp was around 40* deg F or 5* or so C.

The jetting seems to be working perfect for me... No abnormalities that are bothering me... Only thing is the hard starting I have been having, but I am convinced that it is temperature related, and when it is warmer, it will start easily... and if you wack on the throttle real fast on the landing of a jump, sometimes, it will hesitate for a split second, I'm thinking thats more of a "weather" and fuel screw tuning thing, again because its pretty cold when I could ride...

[Hondafmf]

what would your recomindations be for a 2005 CRF 250 full Dr.D system power now, port, polished head 13.5:1 piston, twin air air filter, Twin air backfire screen remover, and boyseen quick shot. i also run 110 race gas. i'm below 1000 ft probably about 300 and the temp normally is anbout 80 in the. every thing is new i havent even had a chance to run the new engine yet and the exhaust has been repacked with running yet also. thanks alot

[sly69]

ive got an 08 crf and im at 45pilot and 185main the top seems fat a little and the bottom seems lean but still is running very good just worried about the starting i noticed i went to 2.5 on the fuel screw and it seems to start worse so im going to try a 48pilot and 1.3/4 on fuel screw bike has 16 hours and valves are in spec,

[packman]

• Ok folks so what about here at sea level in the uk .... im running a larger pump bowl  and a recluse clutch ... tappets are in spec but sometimes a right pig the start ...  motor has 10 hrs on new everything Pro built ... 

Edited December 2, 2015 by packman

[HancockMX546]

I have a 2008 crf250r I am re jetting. I have a JD jet kit, but I didn't have the foresight to also purchase pilot jets. It has a keihin 68 in it currently?!?! I am at 5000 to 6000 feet in Wyoming, it kind of varies where I ride. What would yall recommend for a pilot jet? I have a keihin 175 main with the stock needle and clip position in the carb. Thank you.

Edited November 13, 2016 by HancockMX546

[Garrett McCasland]

I have a 08 crf 250r and am rejetting it and I have no idea what size to go to, I just moved to Oklahoma from Colorado and currently have a 182 main, a 45 pilot and a 68 idle jet. Old elevation was 5,312’ and new elevation is 610’. Thanks in advance!

[mlatour]

23 minutes ago, Garrett McCasland said:

new elevation is 610’

Use stock settings as a starting point.