CRF 150F cuts out past 1/4 throttle
  • Boneman818
    Posts: 3
    Joined: Sun Oct 08, 2017 7:37 pm

    CRF 150F cuts out past 1/4 throttle

    by Boneman818 » Thu Oct 31, 2019 7:30 pm

    Hey everyone, I purchased a new 2016 CRF150F for my son. He got one ride out of it bone stock. I then went thru the power up process: removed airbox snorkel, removed exhaust baffle, purchased from CRFs Only the needle, installed it on the 4th notch, new fuel screw, new pilot and main jet. No matter what position I set the fuel screw in the bike bogs badly past 1/4 throttle. It starts and idles like a dream and I can ride in 1st gear into higher RPM I just can't crack the throttle past 1/4 without it cutting out and wanting to die. Anyone know what the heck I am doing wrong? I confirmed everything is nice and clean inside the carb, I can see light thru the jets and the jets are brand new.
  • Aussiecrf230
    Posts: 1964
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: CRF 150F cuts out past 1/4 throttle

    by Aussiecrf230 » Fri Nov 01, 2019 1:31 pm

    Hi Boneman818 and welcome to the site.
    We just need a bit more info about the bike so we know what we are trying to diagnose.

    Was it running OK before you did the jetting and other changes?
    So when you say new,do you mean brand new or just new to your family?
    If you gently open the throttle past 1/4 does it run OK? There is no accelerator pump on these carbs.
    When you say 4th clip is that from the top or bottom?
    If it is from the bottom then move the clip down to say 4th from the top.
    What main and pilot jets are installed?
    What height above sea level are you, it can make a difference to what jets are used.
    Awaiting your reply.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas
  • Leardriver
    Posts: 462
    Joined: Wed May 05, 2010 10:33 am

    Re: CRF 150F cuts out past 1/4 throttle

    by Leardriver » Fri Nov 01, 2019 6:58 pm

    I agree with Ray's advice. A general rule of mechanical service is to undue the last thing you did, in the case the needle and main jet back to stock temporarily.

    But first... ride it with the choke pulled out. Better or worse? Checking for a fuel starvation issue on the mid and main circuit.
    Also, take the gas cap off for a second right before you pull away. Put it back on first, of course. Checking for a plugged gas cap vent.
  • Boneman818
    Posts: 3
    Joined: Sun Oct 08, 2017 7:37 pm

    Re: CRF 150F cuts out past 1/4 throttle

    by Boneman818 » Fri Nov 01, 2019 9:20 pm

    Pilot: 42
    Main: 108 (currently) also tried 115
    Needle: 4th slot from the top. I also ran factory needle that has only one slot.
    1000 ft elevation
    Purchased bike brand new, only has about 1 hour on it which was with the full factory setup. Ever since I touched it things have been bad.
    Unfortunately I can't reinstall the exhaust baffle or the air cleaner snorkel as I threw them away. I got tired of a garage full of old factory parts so tossed them before testing the bike (I know, dumb). I first started with the just changing the pilot and main jet not the needle. It never ran so I then purchased new needle, pilot, main, and adjustabe fuel screw. I read that removing the snorkel and exhaust baffle you must rejet and ajust the needle so I thought this woud fix it but no such luck. When you pass the 1/4 throttle mark the bike flat out chokes. If you are standing it will throw you over the bars. It doesn't die but spits and coughs. You can open the throttle wide open and it just keeps coughing and never cleans out. The bike does not like to run with full choke at all, 1/2 choke has the same behavior.
    From what I understand the first 1/4 throttle is pilot screw, the 1/4-full is the main jet. I soaked the carb, sprayed with carb cleaner, blasted with 100 psi air.
    Thanks for your help guys. If I can't figure it out I can always take it to a dealer just hoping I could save the time and some dollars.
  • Aussiecrf230
    Posts: 1964
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: CRF 150F cuts out past 1/4 throttle

    by Aussiecrf230 » Sat Nov 02, 2019 4:14 am

    From what you have described it sounds like it is too rich as it transitions from the idle jet to running on the needle, normally about 1/4 throttle.
    If it was lean I would expect the engine to cut out altogether.
    Stay with the 108 main for the moment and move the clip up a slot or two. This will lean it the mixture a bit.

    Just make sure any breather hoses aren't crimped or blocked as this can produce weird issues as well.
    Obviously check the passageways in the carb both fuel and air.

    Lets us know how you go.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas
  • Leardriver
    Posts: 462
    Joined: Wed May 05, 2010 10:33 am

    Re: CRF 150F cuts out past 1/4 throttle

    by Leardriver » Sat Nov 02, 2019 8:07 am

    The main jet only kicks in at full throttle in the upper rpm range. The needle has everything to do with just off idle through 3/4 throttle. The pilot is good for starting and idle, and just off idle, nothing else.
    You description sounds like a needle issue.
  • Boneman818
    Posts: 3
    Joined: Sun Oct 08, 2017 7:37 pm

    Re: CRF 150F cuts out past 1/4 throttle

    by Boneman818 » Wed Nov 06, 2019 7:57 am

    I did one more cleaning but this time let the carb soak with carb cleaner for about 20 minutes. I blew everything out. This time I also pulled the hoses off the air cut valve and blew air thru the valve. Not sure if this did anything or not. I also realized that I was missing the rubber O ring on the adjustable fuel screw. I put everything back together including the missing O ring and it's running great.
    Thanks everyone!
  • Aussiecrf230
    Posts: 1964
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: CRF 150F cuts out past 1/4 throttle

    by Aussiecrf230 » Wed Nov 06, 2019 11:49 am

    Great, your son will be over the moon.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas

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