crf 50 with lifan 125 motor. reving issues Please help!

Hi guys I'm new to the forum I'm having rev issues idles great but won't rev if I crack throttle just wants to die at this point it will ride nice if you easE into every gear like just cruising. But no give it n go.

Hi guys I'm new to the forum I'm having rev issues idles great but won't rev if I crack throttle just wants to die at this point it will ride nice if you easE into every gear like just cruising. But no give it n go.

try cleaning the carb.  is this the PZ 26 that came with the engine or a different carb?  either way, take the carb apart and clean the jets, specifically the smaller pilot jet.

Only thing I see is a 5 in bottom of bowl on inside and on side on the outside of carb it says PD and jing ke. I cleaned it revs okay now but still not right . pops n breaks up a little maybe I didn't clean good enough I know some is tough to get. What are settings for both jets ? In bowl there are three removeables. I removed n cleaned all n should all three be just snug. What are settings for all three and as for idle n air screw. I trued setting to stock specs . was idling before I cleaned carb but not much rev at all without breaking or bogging now its not idling on its own fires right up with 1\4 throttle n revs decent better then before fore sure but like I said still breaking n bogging on higher end revs.

Please help

Hello, I am going through some of the same issues myself. I have the same motor and exhaust. Most of these engines come with a 22 millimeter Mikuni clone carb. Factory jetting is usually a 15 pilot and a 95 main jet. Those jets are too lean for that motor. I got mine to run decent in the summer but now that its super cold here it ran like crap. Far too lean for cold dense air. I don't know your exact setup or where you live but that could be a possible issue.

It would be helpful if you could figure out what your carb is a clone of

Search VM22 for Mikuni comparisons

Where do I measure on carb to determine this. I wanna get this figured out as soon as possible I I can figure out what size n tell you maybe we can figure the problem out. Thanks.

I'm getting just shy of 22 mm where throttle goes in up top and where filter goes on in getting 30mm . I put needle clip all the way on top notch. Now its like coughing gas out of carb didn't wanna rev clean. And it was acting different before when clip was one from bottom. What should I do . It will idle with choke on and rev okay , but with choke off it just wants to cough gas out carb n die out until I let off again n it idles nice with choke on and with it off idle rises. I'm so baffled. Haha. Just wanna get her to its full potential. Thanks

Try posting up a few clear pictures of the carb, so everyone can see what you're working with.


Carb size is measured from the engine intake side where the carb throat meets the venturi area, just in front of the slide throttle.

The carb might have identifiable engravings on it if you look closely.

Does your carb have an adjustment screw on the bottom side located by the intake?

 idle issues are usually air leak related for the chinese carbs.  run a test and spray carb cleaner on and around the carb while it is idling/  changes in RPMs indicate a leak somewhere.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By RCWSO
      I have an 07 CRF70 that I have done the filter pod modificaiton by cutting the extension tube off and I have drilled a couple of holes in the end of the exaust per some instructions on a thread here at TT.
      I have recently had some problems getting the bike to idle consistently. I am wondering if I should try and rejet the bike at all or get a needle from an older carb that is adjustable. I do have a unifilter that I can put in as well with the stock pod that I cut.
      It is not that the bike wont run or start, it just seems to only idle if I turn it up significantly but as soon as I turn it down even 1/8 of a turn it dies. But the idle that I set to keep it running well is too fast as the bike will move forward if in gear and no throttle is applied.
      Any suggestions? Jetting, needle, air screw change with an older carb?
    • By the-new-kid
      hello guys I'm like really new to this, like extremely new but I was going to buy xr-70r from a friend and drop a Lifan 125cc engine in it (here's the link: ). Now the site says its a 4preed trans with normal gear set up (1-n-2-3-4), and manual front clutch, I'm wondering if I need to buy the clutch lever, perch, and cable then connect it all. Then secondly, what pip should I be looking for I'm not sure if the header would have to be a different style or what exactly.... please be patient with me I'm doing the best I can to learn... thanks
    • By anger806
      hi im new to the forum and i am running a stock 2005 crf 50f with pro tapers but no engine mods what size carburetor should i be looking for to get a little more pep out of my motor?
    • By HondaRacer37
      Hey everyone.  Darn glad to have found this forum!
      Just bought my son a 2009 CFR70 (first bike - 8 years old) and the first thing I'm doing is scrapping the factory air box for a UNI pod filter.
      I'm looking for advice on how I can open up/modify the factory exhaust for more performance.  I heard about removing the screen and drilling some holes but have not found those posts. Any specific advice would be greatly appreciated. (Found only a couple performance aftermarket pipes that were very pricey.)
      I'm thinking after the air filter change and pipe opening the main jet size may need to be increased. It's a stock 13mm Keihin carb.  What size is recommended?  Haven't looked at the stock size yet. 
      I assume the needle is adjustable on the slide (but don't know if this would do any good or be necessary anyway) and hope there is an air mixture screw somewhere because it seems the carb could use a bit of adjustment now.  Although next to the idle screw it looks like a brass cap or plug rather than a screw. (See photo attached.)
      Thanks for any advice.  It's great to be part of this group.  Ride on!
      Greg in Florida

    • By thousandbuckle
      Hello all, reaching out to you today to get some help with a small project I am trying to do.
      I just bought a 2006 CRF50 for my 3 year old and would like to rig it up with a wireless remote kill switch for those just in case moments. I have the throttle speed screw installed and will limit it that way also but want a back up until she is proficient and I feel confident.
      Since this bike does not have electric start there is no battery. I was wondering if any one has or knows how to rig up a wireless car alarm system to work as a remote kill switch. I know I will need a 12 Volt battery on the bike which I can get. I know there is a product from 3Built that does this but the range is only 250 feet and some say it is even less than that. I was thinking of a car system since the range is usually around 1,000 feet which is overkill but I prefer overkill when it comes to this topic,
      Any DIY thoughts you might have or suggestions would be appreciated.