Accelerator Pump Mod

There is a sticky thread in the CRF450 forum that addresses a linkage mod to the AP. The thrust is that this mod noticeably improves engine response to a quick snap of the throttle. It eliminates the boggs and the results were overall favorable, even greater in the CRF250. As I viewed the threads and photos, I'm thinking that this looks alot like the carb on my 02, 426. We have a mild case of the boggs and am looking for a cure plus easy extras. I have not seen AP mods addressed in this forum, are there any. What say you?

It has been covered, even more lately that JD kit now contains O-rings for this specific reason.

Have you done the BK mod? It is specifically for your bike (YZ/WR426's) as you don't have a leak jet for AP squirt adjustment.

You are not going to get an easier fix.

There was even a thread on this very subject not more than a week ago.....

I have not seen AP mods addressed in this forum, are there any. What say you?

No offense, but you haven't looked very hard then...SC

Today I focused on the AP timing, opened the cover, read the service manual (SM) and attempted the operation. I found the SM to be very confusing. If the adjustment is made to my interpretation of the SM, the AP does not function at all. The SM says, "insert the 3.10mm rod", I did. "Fully turn the AP adjustment screw. Check the link lever 4 has free play by pushing on it slightly. Gradually turn out the adjusting screw while moving the link lever until it has no more free play".

Well, as I understood it, I backed off the adjusting screw until there was no more free play in the link lever or the push rod link lever assembly. This meant that the adjusting screw was just touching the link lever. This also meant that the AP was at the bottom of its stroke w/ nothing to pump.

As I twisted the throttle, there was no visible squirt of fuel. After reassembly & try out, the bogg was terrible. Taking a WAG, I turned in on the screw 1 1/4 turns and tried again. Much better, "almost' no more bogg.

I have to understand this and I don't. Please offer some direction. Thanks

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