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Guest mxrider426

accel pump

5 posts in this topic

Was anybody else's accel pump adjusted wrong by the factory? I understand that you loosen the adjuster screw till the freeplay goes away. Mine was screwed in too far. Could this be making my bike run lean? It is lean at all throttle openings, so I figured I should adjust it before I messed with the jets.

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If you are talking about the AP pump TIMING screw, I would caution you against adjusting it willy-nilly. It will drastically affect your throttle response. If you do adjust it, do it no more than a 1/2 turn at a time, then RIDE the bike to see if it helps or hinders.

Yes, if the timing of the AP squirt is such that the squirt is late, then it will be lean when you first open the throttle down low or off-idle. You need the squirt to get that snappy low end response. But, the squirt only lasts for a second or two (in stock form, depending on the year of your bike), then the jetting takes over. Additionally, the AP does not do anything at a constant throttle position. It's all jetting at that point.

Take the carb loose form the air boot and let it hang by the throttle cables. Twist the throttle and watch what happens with the AP squirt. This will help you understand it.

See the thread "Jetting 101" on the 250 side for help getting started with fixing your "lean" issue.

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Man I'll tell ya what, I was suprized by the distance that sucker would squirt for sure!

I have a feeling the accel. pump need to be dialed in after purchase. I did the bk mod and it seemed like I got more performance out of getting that timing right than I did the bk mod. I set my pump timing screw with the engine running. Basically, blip, adjust, blip, wrong go the other way, blip, Hmm-better, little more, blip, HOLY COW! Then it was something like, HEY SHUT THAT DAMN THING OFF!. Oops, sorry, didnt realize it was 10:30.

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But watch from the BACK side of the carb. A nice shot of gas will squirt out the front of the carb (don't want to get that in the face!).

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