Pilot screw on yamaha 15

Discussion in 'Outboard Maintenance' started by AfterHours2, Jun 27, 2011.

  1. AfterHours2

    AfterHours2 Stripper in my own Mind!

    A new pilot screw was included in my carb kit and I have done some research as to how to remove cover placed over by the factory per EPA requirements. My main question is should I have removed the old pilot screw, cleaned interior with carb cleaner and replaced with the new one? I know it is an air/fuel ratio adjusment but not too sure if this really makes much of a difference in the performance. I plan on removing this evening by running in the old one gently and counting the turns for proper adjustment. I just did not want to go through this process if it was not going to benefit the performance of the motor... Thx
  2. Brett

    Brett > PRO STAFF <

    I've been told never to mess with the sealed air mix screw,
    and I've been told that without removing it, you can't be sure that the carb is truly cleaned.
    I guess it depends on your confidence in how well you can adjust a carb.
    If the engine runs properly without removing the plug, then leave it alone.

  3. cutrunner

    cutrunner Cert. Yamaha technician

    Not worth it. Heres why. If the motor was purchased at a retailer tht is at or close to sea level then the adjustmebt is very close to perfect.(motor sales very from sealevel) and, its so close if u were to lean it out it would do much at all maybe 1/4-1/2 a hp, since it only controls the idle circuit. That and the small motor are very finicky.. But its your motor
  4. AfterHours2

    AfterHours2 Stripper in my own Mind!

    The only issue Im having is this, with a full soaking and cleaning of the carb including rebuild kit, the motor still does not want to run under load to its potential. The coils have been checked and are running to par including new plugs. New fuel line, tank, fuel pump and connectors including the one on the motor. Compression test was +/- 1 psi on each cylinder difference which seems sufficient. The only thing I could think of was that little pilot screw left over from my rebuild kit and cleaning inside area of carb. That was my last resort. I might add, fresh non ethenol fuel and yamaha oil was used in the proper 100:1 mixture. I thought I had this thing fixed in the past but it continues to give me trouble. Thx for the help.... :-/
  5. twitch

    twitch Well-Known Member

    When I clean or rebuild carbs I always drill out and remove the plate on the pilot screw, it is the only way to be sure all passages are 100% clean. [smiley=2cents.gif]