[mustang]

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.

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 !

[Cappy]

Just rejetted my sons 2006 150F
MOds:
target altitude: 5000-7000ASL
Open air box
Twin Air filter
Spark arrester back pressure plate removed
Main Jet: 150
Idle jet: 40
air screw: 1 3/4 turns
needle clip pos: top ring

[zak13]

Just rejetted my sons 2006 150F
MOds:
target altitude: 5000-7000ASL
Open air box
Twin Air filter
Spark arrester back pressure plate removed
Main Jet: 150
Idle jet: 40
air screw: 1 3/4 turns
needle clip pos: top ring

really
wouldnt that make it run very lean

[Cappy]

Well at anything under 5000' I'd say yes, but in a 5000-7000'ASL area it runs perfect with very little popping.

[Cappy]

OK...the 150 was a misprint, we were actually using a 130. However, it began to cut out on the top so reducing to a 42 idle jet and a 120 main cleaned it right up.

[zak13]

whered you get the 130 from

[Cappy]

I had it on hand from some other application but it is just a Keihn standard 130 main jet.

[T Man]

I rejetted my sons 05 150f as suggested, and removed the air box snorkel. 115 mj and 42 pj. The bike has a pro circuit pipe.

A friend suggested I should adjust the fuel mixture screw. Any suggestion for best setting?

[mustang]

start at 1 1/2 turns and try opening it a little , you are looking for a "HAPPY " sounding idle speed

[kpotratz]

Mustang

2008 crf 150
Im @ 2000'
temperature 50-70 F
what would be the proper set up to do .

Thanks
Ken

[MOSPEED]

The power-up kit worked perfectly! My 150 starts instantly now. Thanks Mustang!

[kyle7683]

What should the fuel screw be set to?mines at 3.5 turns out now and I still get some hesitation when full throttle applied at idle and while riding

[saefabri]

I used the JD kit on 2013 CRF150RB
Now bike starts easier
No hang on idle
Did not have to remove the carb though.

[Cameron Clontz]

If I just bought a 2004 Honda crf 150f and I want to put a pro circuit t4 full system what do I need for do to the air box and carb?