What do you think about the Merge racing Accelerator pump spring?

Fuel & Air Carburetors & Accessories Merge Racing Technology APS Accelerator Pump Spring

7 replies to this topic
  • Family Man

Posted February 27, 2008 - 12:34 AM


What do you think about the Merge Racing Accelerator pump spring? It sounds like a good alternative to wiring the linkage shut on your AP. I havent noticed bog on my unmodded AP but I am curious.

  • grayracer513

Posted February 27, 2008 - 07:14 AM


Stiffening the AP drive spring is the right way to address the problem of the spring being too weak. This is essentially what using an O-ring on the linkage does; increases the force applied to the pump rod while retaining the ability of the rod to come to a stop without binding the linkage. Wiring mods are kind of a "caveman" approach to the issue, IMO, and I don't recommend it.

But like you, I have no bog problem, nor does my son complain of one (I have asked him specifically about it), so I don't worry about it myself. The spring is the right way to go.

BTW, the '08 models already have a stiffer AP spring than the older models did.

  • Holigan

Posted February 27, 2008 - 08:41 AM


Our spring has one less coil than the standards OEM so that we can use a thicker wire to make the spring stiffer. We believe that is the proper solution to fix a problem that should not really be a problem. The '07 and '08 Honda's don't need our spring, they are setup correctly.

Transworld MX will have test results in the next issue on a test they did with our spring, our ALJ and our new fuel mixture screw. Check it out to see what they thought.



  • Family Man

Posted March 15, 2008 - 12:14 PM


Has any body tried the Merge
Ap spring yet? If so did you have to mod any thing else to go along with this mod or is it a standalone, do you have to change your leak jet with the mod etc?

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  • grayracer513

Posted March 15, 2008 - 03:15 PM


You might find that the overall performance is better with a slightly larger leak jet to balance out the more positive delivery coming from the pump when using the stiffer spring. In general, I think that is usually the case.

  • tcheck

Posted March 16, 2008 - 10:52 AM


just installed merge racings spring and the adjustable accelerator pump cover. Runs like a rocket now. I thought my bog was next to gone before i installed these two. Wow after I installed this i realized it was not even close to gone. now no hezitation no need to feather the clutch as much. very easey to install ONLY USE CAUTION when using there supplied drill bit very brittle and broke off inside the hole when drilling. I recomend using a better bit.:confused:

  • Thesolidman1

Posted March 01, 2010 - 06:32 PM


Hi, I just installed the spring on my '06 YZ450, rode it today for the first time. My bike is stock, except for jetting and flywheel weight. My thought was, if the factory updated the spring to stiffer on the later models, and guys are wiring the linkage, it probably is worth a try, especially at $16 and about 1 hour of time. Well, I rode today on a local MX track, and did find the bike responded quicker and puller harder from the bottom out of corners. I am pleased with the difference the spring makes, and think it's worthwhile. I know your question is quite old, but perhaps someone can benefit.....

  • kawasakimx8

Posted March 01, 2010 - 06:38 PM


i instlaled one in my 07 kx250f and didnt help at all.

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