Accelerator Pump Spring Tension??

4 replies to this topic
  • Pothole

Posted October 21, 2004 - 11:51 AM


On my '99 YZ400, when I manually depress the pushrod cam while opening the throttle, I get a good squirt, but there is hardly any squirt if I don't depress it manually. Has anyone increased the spring tension of the pushrod to fix this problem?

  • moburki

Posted October 21, 2004 - 11:57 AM


I haven't increased spring tension, but I have a similar problem on my 2000. If I manually apply pressure to the AP cam, it improves response (less bog) when I wack the throttle. I was thinking about doing the same thing, or decreasing the pressure from the diaphram spring :cry:

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  • Pothole

Posted October 21, 2004 - 12:01 PM


Yeah, I've done a number of searches here on AP spring tension with no results. So, looking at it, it appears you can take the end of the spring that is hooked to the throttle linkage, bend it 90 degrees and rotate it 180 degrees clockwise (tighter) and hook it to the top part of the throttle linkage. I've heard from a mechanic that this was a trick they used with the older DRZ's, which had the same carb.

  • moburki

Posted October 21, 2004 - 12:57 PM


I'll take a look at it, maybe give it a try. Let me know if you do it with success (and pics) :cry:

  • WR426madness

Posted October 21, 2004 - 01:45 PM


Here's the fix remove the spring and cut it of at the bend for the A/P side and rebend it, this should shorten it 1/4 inch. I did mine and bam, no more dead spot.

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