Alternative to the Merge Racing spring for a 2006 450x?

Hey guys. Just picked up a new-to-me 2006 450x. Lots of bog down low; looking to get a Merge Racing spring. I don't want to do the o-ring mod. Nobody carries the Merge spring for the AP, and those that claim to, want $30 or more to ship to Canada. Is there an alternative? Can I run a spring from an 08 or newer X?

You can't run a spring from the '08 and newer X's as the design was actually changed.


 I've seen a post or two for alternatives to the Merge spring, but don't remember the name off-hand. 



The best option is this.

Get yourself an 08 accelerator kit, an o-ring kit (carb re-build kit), and a new floating plate seal.

Take the carb out and strip it down to the body but dont separate the halfs.

Pull all the jets, the emulsion tube, float and needle.

Clean every orifice and passageway and inspect with a flashlight and or magnifier to verify everything is working correctly.

Take extra time to fill carb with fuel and manually operate the accel pump to see squirt, it should squirt a good couple feet out of the front of the carb.

Set your fuel screw to about 1 1/2- 1 3/4 turns out and jet for your altitude.

Use OEM parts.

If you do this your bike will run great.

Edited by Dust_Devil

Tokyo mods also made a stiffer spring.

The Tokyo mods spring works even better (stiffer(


The 2008 linkage spring does not work on the pre-2008  carbs

Awesome, thanks guys. I'll look into the Tokyo Mods one then.

I have an R&D spring in mine off a later model just had to bend a tang to get it to fit. If you don't fit the later accel pump parts make sure you grind the rivet as it affects the arm at WOT. Check the jetting thread there is a heap of info there, just follow it. Mone still was not quiet right after  all this so in played with the Accel pump timing at less and slower openings then the watch it squirt method. I now hve NO bog and NO flame out.



Edited by MartyMOOSE




Edited by Jim Dettman

Just to be clear on "later" model, after 2008 the overall design was changed so that the spring stiffness didn't matter.   Here's a photo of the two designs side by side:




The old style is on the left, new design on the right (if you click on the photo, you will be able to see it decently enough to see what I am talking about).  What you looking for is the black plastic arm in the middle of the photos. It's right below the big round object at the top.


This arm is what is connected to the AP rod.  In the old style, the tab on the arm that contacts the adjustment screw is on the left and the head of the adjustment screw is on the right.


 In the new design, the arm contacts the screw on the right and the head of the screw is on the left.


Now understand that this linkage rotates clockwise when it engages, pushing down on the rod that connects to the AP.   It rotates counter-clockwise when you let go of the throttle and it disengages.


 So in the old design, the linkage pulls away from the arm, which means the arm needs to get pulled along by the spring.  In the new design, the linkage pushes against the arm, so it doesn't matter how stiff the spring is, 



Edited by Jim Dettman

This link has most everything you might be looking for including the Merge spring. Not sure about the Canadian shipping.


Another alternative to the Merge spring is the one from Tokyo Mods. Other than that, I don't think anyone else offers them anymore. R&D Racing used to offer one but no longer do.


I know the OP was thinking Tokyo mods so if he can do that, great. If he needs shipment to Canada, Ken over at will ship to Canada, and his service is exemplary, and prices are compeditive. His site is a regular resource for me.

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