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Thread: Pro 15 carb ?'s

  1. #1
    RC Racer
    Join Date
    Mar 2020
    Southern Illinois

    Arrow Pro 15 carb ?'s

    So I have a few 15 carb ?'s. I stall my engine every time I accelerate at full throttle, after replacing the crankcase on my engine. I figured, well, I ought to re tune. So I figured I'd set everything to factory settings. When everyone says 'flush with the throttle arm' how many turns out is the screw? How many turns out from all the way in should the screw be, to be 'flush'? Also, is an aluminum header and tuned pipe (#4485) worth the $50 from the LHS?
    I'm not afraid of my fellow man.

  2. #2
    RC Qualifier nebulous.cow's Avatar
    Join Date
    Feb 2012
    Seattle by summer, AZ by Winter
    The needles when flush with the throttle arm are not a specific number of turns out from closed. Due to manufacturing tolerances, it's likely to be slightly different across multiple of the exact same carb. One may be 2.5 turns out from closed, and another may be 2.75 turns out from closed.

    It's worth noting that on slide carbs like the 3.3 carb, the low speed needle would need a different number of turns out from closed to achieve the same factory setting if the idle gap is not exactly identical. Now the Pro 0.15 is a rotary carb, but the principle is the same. This is why almost every factory setting for a low speed needle is "Flush with _____" instead of a number of turns out.

    When setting the needle flush, use your eyes and look as closely as you can. Sometimes metal straight edge to hold over the needle screw can help you figure out exactly where "flush" is. But it shouldn't need to be EXACTLY flush down to the micron, just as best as you can do should be fine.

    As for the pipe, I actually use that pipe on one of my touring 0.15 engines, and it's quite good. Not sure how it would compare to the stock pipe on your motor, but that pipe isn't too bad for general purpose use. The Pro 0.15 isn't exactly a powerhouse of a motor, but a good pipe can boost you a little bit. I wouldn't expect night and day differences though, but if you want to try out something new, can't hurt.


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