Carby jnmotors racing carb HELP!

Discussion in '2-Stroke Engines' started by battery, Apr 1, 2014.

  1. battery

    battery Member

    I bought this racing carb from jnmotors and it is running very lean. I only see two screws on it one for idler which I adjusted the other I have all the way unscrewed. It seems to be running lean. Engine gets hot and it its over revving for 20 seconds after I let off the gas! Due anyone have any info or can help me adjust this wabron carb? Not walbro, but wabron...

  2. battery

    battery Member

  3. Fabian

    Fabian Well-Known Member

    If you only purchased the Walbro style diaphragm carby, you wouldn't be having these problems.
  4. jaguar

    jaguar Well-Known Member

    you unscrewed the idle air jet which makes it run lean at zero throttle
  5. battery

    battery Member

    I agree fabian. Im an idiot for buying this. but have the idle screw (b) correct. I run around town at full throttle 95% of the time. its screw A that I am having trouble with. it seems to do nothing at all. I was running with it all the way unscrewed and it ran lean. I screwed it in tight and saw no differance. my engine ran really hot and had trouble slowing down. if I pull the clutch the bike would over rev unless im off the throttle for about 20 seconds. I think Im going to toss it. I put the stock nt back on.
  6. Fabian

    Fabian Well-Known Member

    I could be wrong but "screw B" appears to be an air bleed screw, possibly for idle air/fuel mixture adjustment.

    Screw A appears to be a throttle slide idle speed adjustment. I have no idea what all of the other hose fittings control.

    After trying a Genuine Delorto SHA and a clone Delorto SHA, i found no throttle response or power improvement over the NT, so i went back to the original NT carby as i found it to be more user friendly when jetted correctly.

    The most significant improvement was the Walbro style diaphragm carburettor, because it has external jetting screws, making air/fuel mixture adjustment a very simple and mess free job.
    A diaphragm carburettor just runs properly and stays clean, as it doesn't suffer from air or fuel leaks.
  7. Fabian

    Fabian Well-Known Member

  8. battery

    battery Member

    I dont want to dump too much more money into this bike till I get another for getting around town as I know it is getting impounded one of these days. I think the best route would just to be to re jet the carb. the one thing I like about it is that it has a bigger intake. but I am fairly disappointed in jnmotors for selling such crap. makes me question what else they are selling. I will certainly check with you freinds before making any more stupid decisions. as my bank account has run dry due to my stupidity.
  9. Fabian

    Fabian Well-Known Member

    So long as you can get a circuit diagram of how the "racing" carburettor works, it shouldn't be too difficult to set it up to meter air and fuel correctly.

    It's just a matter of emailing JN Motors to find out how the circuits work, then making the necessary adjustments or corrections.
    Once that's done, the carby should work reasonably well.
    battery likes this.
  10. HeadSmess

    HeadSmess Well-Known Member

    the screw does nothing.... in other words, either the circuit is blocked, the sounds of it, the pilot circuit is too lean.

    get a bigger idle circuit jet. or a set of microdrills :)

    or unblock the jet. iunno.
  11. butterbean

    butterbean Well-Known Member

    I'm curious as to why you felt you needed a "racing" carb for "getting around town". Perhaps this has something to do with why you're "sure your bike is going to get impounded one of these days"?