A/F screw falling out?!?!

6 replies to this topic
  • yamahaboy99

Posted March 25, 2006 - 01:36 PM


While tweaking the carb today for tomorrows ride, we were adjusting the A/F screw and sometimes it would just fall out. Luckily we had all the parts sitting on the motor every time they fell out. Its 35 degrees out, were running the 165 main jet with 2.5-3 turns out on the A/F screw. Should I be worried about it falling out tomorrow?

  • kilgore trout

Posted March 25, 2006 - 01:47 PM


Make sure the spring and o-ring is still in there. If not it will continue to fall out.

  • NYMXer

Posted March 25, 2006 - 01:54 PM


Your turning the screw out to give the motor more fuel at low RPM's. Get a #48 pilot jet and that will let you turn the screw in more. These bikes come lean on the low pilot circuit. I put a 168 main in mine and raised the needle jet to the 4th groove. Fuel screw is at 1 1/2 turns and the bikes runs sweet. I also added a Uni filter. :thumbsup:

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  • yamahaboy99

Posted March 25, 2006 - 02:37 PM


Spring and O-ring are still in there, I dont have any pilot jets so I really cant change that. We were trying to get rid of the backfiring, which seems to be gone now. Any other advise?

  • PK

Posted March 25, 2006 - 02:51 PM


I wouldn't go out anymore than 2 1/2 turns on the fuel screw. That seems to be the point the fuel screw spring loses the tension on the fuel screw and after that happens it falls out. I would rather deal with a little popping than have the fuel screw fall out. You need to get the correct pilot jet when able for the correct fix, as I'm sure your aware...

  • yamahaboy99

Posted March 25, 2006 - 04:31 PM


The screw was at 2.5 turns so we turned it back into 2 just to be safe. Thanks for letting me know about how far they should go out. I thought there was a problem with my bike or something.

  • ovrrdrive

Posted March 25, 2006 - 07:54 PM


You should be ok out to about 3 turns on the screw...

Try stretching the spring out a little to apply more pressure on the threads. It should be ok.

I did hear about one guy safety wiring the screw, but have been unsuccessful in getting him to post a pic of it...

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