accel pump question



1 reply to this topic
  • yzf322

Posted February 02, 2002 - 04:42 AM

#1

What advantages would i have if i adjusted the accel pump screw without doing the BK mod,what happens if i turn it in or turn it out, im new to he game and im just trying to figure it out.............42pj-165mj-needle stock pos.-fs2 trns out...........

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Hick

Posted February 02, 2002 - 10:32 PM

#2

If you are talking about the adjusting screw right next to the slide pulley that comes with the Yamaha-only Flat CR, turning it changes when the pump begins to deliver fuel relative to the slide position. In, or clockwise, increases the delay and out decreases it.

So I guess you could call it the pump timing screw.

If you turn it in a half turn from stock you should notice a little lean/dead spot when you first crack the throttle. If you turned it as much as a quarter turn out from stock the fuel stream would probably hit the slide momentarily, resulting in a few drops of un-atomized fuel added to the mix.

The reason this screw gets mentioned in conjunction with the BK mod is that it usually works better with an eighth or quarter turn of additional delay on the timing screw.

If you start foolin' with it and forget where it was, there should be a dab of green paint on the screw head and spring that need to line up. Barring that, with the carb off, or with the sub frame and air box off but carb still installed, adjust the screw so that the stream from the pump jet just clears the slide as it goes up.

Hope this helps.

:)





Related Content

Forums
Photo
Motocross

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
Forums
Photo

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F


Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies
Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.