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The CRF150F comes from Honda very lean in the idle circuit and this makes starting a cold engine very difficult .
The following change to the bike will give you a mild boost in power as well as a much better running 150F , that will start easier and actually IDLE without stalling .
and it will only cost you about $40
You will need the following items :

-99103-KPT-0420-Slow jet (42 being the size, stock is 40)

-99113-GHB-1150-Main jet (115 being the size, stock is 98 )

A good hi flow air filter like a twin air or no toil or uni , etc , etc.

You need to start by removing your seat from bike .

1. Remove the rubber snorkel from airbox , just grab it and yank it off .

2. Remove the baffle from the end of the exhaust pipe , drill a few 1/4 inch holes in the solid steel plate on the inside end and reinstall it in bike , Now it will breathe a little better and you will still have a quiet bike .

3. unscrew the cap where the throttle cable goes in the top of carb .

4. pull the cap and slide that is attached to the cable staight out .

5. now you can change the needle , but you really don't have to change it just move the clip to the fourth notch from the top of the needle if it isn't already there at the fourth notch.

If you do want to change the needle use part number -16012-KPT-921-Needle set (on the middle clip) .


6. unscrew the band clamp on the air boot at the rear of carb , remove the two 10mm nuts that hold the carb to the intake manifold .

7. now you can remove the carb from bike (make sure to unhook the vent tube from the clip on the frame

8. Turn carb upside down over a bucket and gas will drain out .

9. remove the philips screws from the bottom of the carb on the float bowl , remove float bowl and you can now see the main jet and it has a little plastic pc. around it that has a notch in it for the pilot jet clearance

10. replace the main jet and pilot (don't overly tighten or you will break them off in the carb body, not good)

11. reassemble the reverse of above and you are done except for fine tuning the fuel screw after you get the bike running .

12. Replace the air filter with a new one , like a twin air or no toil etc. don't use the sponge that honda sends with the bike

you're gonna like the way it starts and runs now !

Finnally, a sticky, well done.

when you dump out the fuel over a bucket, does any parts fall out

When taking the float bowl off and dumping the gas from it, just be careful of that little plastic white piece inside it (goes notch off center)...it falls off easy. Me and my carburater have become very close recently, as i did the rejetting to my 230 and had some issues, ended up takin that carb apart about 20 times. Good Luck!

where do you get the jets from and how much are they?

tried this set up and it falls on its face at mid throttle and the plug gets dirty real quick. should i try a smaller main jet ???

It probably wasnt jetted right for your elevation, try asking around in the jetting forum for the correct jetting for your elevation.

looking for input please,
I just bought 2004 150f with dmc alien pipe (load very open,needs quiet kit!),uni filter, snorkel removed. Pulled carb off last night to see what jetting was done because off idle it feels very lean and plug does not have color (thought maybe not jetted).
found:
115 main jet
42 pilot jet
needle on 4th clip up (rich)
idle screw out 2 3/8
pilot screw closed (turned all the way in)

I tried,moving the clip to recommend 2nd clip (leaner)
and turn out the pilot screw. I falls on its face hard if you grab a hand full off idle. if you hold it up off idle and snap it it is better. the bike has very poor low end my son said the front wheel wont come up like the 100r does.
Please respond with any sugestions....

rocketman wrote:looking for input please,
I just bought 2004 150f with dmc alien pipe (load very open,needs quiet kit!),uni filter, snorkel removed. Pulled carb off last night to see what jetting was done because off idle it feels very lean and plug does not have color (thought maybe not jetted).
found:
115 main jet
42 pilot jet
needle on 4th clip up (rich)
idle screw out 2 3/8
pilot screw closed (turned all the way in)

I tried,moving the clip to recommend 2nd clip (leaner)
and turn out the pilot screw. I falls on its face hard if you grab a hand full off idle. if you hold it up off idle and snap it it is better. the bike has very poor low end my son said the front wheel wont come up like the 100r does.
Please respond with any sugestions....

with the pipe you have it sounds like a wide opeen one and on a 150 it will detract from low end torque even worse than the stock pipe for bottom end . sounds like you are to lean all over the range
with the FS out 2 turns or more suggests bigger pilot I would try a 45 pilot and maybe a 120 main (although a 115 is probably the biggest you will find for a 150)
maybe the 230 carbs are the same and you can get bigger , don't know . would put the needle clip back in 4th notch or maybe 5th

what jetting do you reccomend for an xr100r

zak, what have you done to your bike?

Mustang,
I have a quiet kit for the pipe coming that will restrict some flow i'm sure, do you think that will help with the bottom end? the pipe tech guy said i would loose some power with the quiet kit but its going to be a problem anyway, i think he said the pipe is 102db (ouch!)

i wanted to do that on my bike, before I realize that this bike dont worth putting money on anymore cause I am selling it

rocketman wrote:zak, what have you done to your bike?

i always for get that but i have removed screens in both intake and exhaust have a uni air filter and thats about it

well back to the original question, 150f jetting?

Last night i installed a 45 pilot jet (one more size up) Moved the needle back to the 4th slot (rich)
it feels a little better, but it still chokes on it self right off idle, how often do you ride off idle?i don't know. out of the hole it pulls good,rode it down the street to top out and get a little flutter up top 5th gear (maybe rev limiter)

Maybe i expect too much! my 250x hits sooo hard right off idle and i guess i am looking for that?

I am reluctant to go to the next size pilot jet three sizes up sound huge.

What should i expect from idle up?