2007-2009 WR450F accelerator pump help..

Hey guys, Im new and have been scouring TT for a while now and Im having trouble finding some info on the "timing" of the AP on my new '09 WR450F. I did what the servce manual said: threw a 3mm dowl under the float, turned the AP adjustment screw all the way in, checked for play on the linkage, then pushed lightly on the linkage while turning the screw back out till there was no more play. The bike is still boggy on the bottom end. Im at 5300' altitude and I just threw an '09 YZ450F pipe on it, modified the throttle stop and pulled the good ole grey wire. The bike still boggs. She has stock jetting but I figure that would be fine seing how it comes tuned for sea level and Im at a mile high.

I was thinking of doing the Boysen quick shot aswell, does anyone run one of these? Any help would be great. Thanks in advance!

Try the o-ring mod and maybe a smaller leak jet, Im at 5000 feet and it runs great all the way through the power band. If you have not rejetted yet do that when you pull the carb it will really help the bike.

What are you running for jetting?

What are you running for jetting?

The bike it uncorked/freemods, but all stock. Im at a 165 main, 40 leak, 48 pilot and JD blue needle #4 and the smaller oring on the a-pump.

The bike runs great, no hesitation or bog. I think it is getting a tad rich though with the weather getting warmer, so I am planning on running the red needle with a 50 pilot and I may go down a size on the main too. Especially with some of the foothills starting to get free of snow:banana:

hope that helps

Regarding AP timing. The drill road under the slide adjustment (not under the float) gets you 'in the ball park'. A small leak jet (#40~#55), the oring mod (or stiffer AP spring) is ground zero. Next, the thre throttle wheel cover off, go for a ride heat the bike up. Pit, turn the AP screw in (clockwise) 1.2 turn, ride and test. Repeat till the bog just goes away. Usually, not more then three turns are needed.

Keep notes of how far you are turning. Do not test just by reving the throttle at a standstill. Testing must be done during normal riding.

Do not mess with the jetting unless it needs it. Almost never, unless you experience massive changes in temperature or elevation (40 degrees, 2,000') does the pilot, needle or man need to be changed out. Always test instead of guess. A 50 pilot is richer than the 48. I would of thought you'd be running a 45 or smaller in CO.

If you haven't visually checked the duration and timing of the fuel squirt, do that first before making any more changes. What you are trying to obtain is a good strong squirt around one second in duration that just misses the bottom of the slide as it lifts up.

If you haven't visually checked the duration and timing of the fuel squirt, do that first before making any more changes. What you are trying to obtain is a good strong squirt around one second in duration that just misses the bottom of the slide as it lifts up.

Yes, I did that when I did what the service manual said. Its squirts right away, just missing the slide. I couldnt tell you how long it squirts; I have not done any video taping and what not like many others have done.

William 1, 45 or smaller on the pilot.. Well mayb ill throw that extended mixture screw in the carb and play around with the stock 45 this weekend. They tell me that it should run good from 1.5 to 2.5 turns out on the screw and no more? How about the main? its a 162 now, I have an '09 YZ450F exhaust, uncorked, AIS mod ect..I figured the 162 would be fine for 5280 to 9000'.. The bike ran fine when I rode it stock, just a little bog down low. Thats why I did the AP timing deal. The carb is out of the bike now, bringing it to work to throw in a YZ450 throttle stop screw and o-ring the AP arm.

Thank so much guys! Any other info would be great.

coxr650l where are you from in CO?

Yes, I did that when I did what the service manual said. Its squirts right away, just missing the slide. I couldnt tell you how long it squirts; I have not done any video taping and what not like many others have done.

A video or timer is not necessary to 'time' the squirt. What you are looking for is a short burst no longer than a second.

Blue #5 sounds awfully rich even at sea level. I run a red#4, 168 main, 48 pilot and a 100 pilot air jet and a 60 leak jet at sea level on my '08. Bike has a YZ header, FMF factory 4.1 can, ais removed and the acv disabled. Runs like a champ!

Im in Thornton. And I siad Im running the JD blue #4, its actually #3. Do you have an adjustable needle?

I missed the part where the op said he had stock jetting. Two words - ditch it! Don't event try to mess with the ap until you have the jetting at least reasonable. The stock setup is way lean so it will pass emissions.

Is 48 pilot stock in '09? On my '07, stock pilot was 45. I'd try the 45, easy to change, go from there.

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