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new04450

Will the boysen pump help?

5 posts in this topic

I have an 04 wr450,and have done all of the free mods- Since I do not ride in state parks, I took out the muffler baffle, and bike really runs well.- But I do have a small stumble down low. The info I read says the boysen pump will stop that. I have not changed the needle valve position, and I did not touch the mixture screw. My plan is to get the after market mixture screw, and the pump. Being farly new to this off road hobby, I figured all ofthe experience here could help- Do you folks think that these 2 mods will help? It is such a small hesitation, I really did not notice it- until I rode my friends 06 wr with all of the mods, including the GYT-R pipe and jet kit. So of course now mine is a slug :applause: I should have stayed off of it. :banghead:

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Your '04 should have a touch more pop than your buddy's '06 since Yamaha slightly detuned the motor in '05 to give it a smoother power delivery. It sounds to me like you're not quite jetted right and you may want to get the JD kit and Zip-Ty fuel screw. The Boyesen Quickshot is supposed to help with the off-idle bog, but a change in the leak jet may be all you need. If you're not running a #40 instead of the stock #50 jet, then try that before dropping the $$$ for the Boyesen. Check out Indy450's jetting chart in the jetting database for a great place to start. Chances are you won't need to modify the settings from the chart and your bike will run like a striped-ass ape...SC

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Thanks- She runs like a scalded ape now- Just that darn slight hesitation- So I will look at that- Like I said it is ever so slight- I would have never noticed except when I rode the 06 fully modded

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Try to get everything as close as possible with jetting first and then go to the Boyesen cover if you still feel the need. Lots of people will say the Boyesen cover doesn't do much, others say they like it. I think it helped my low end bog a bit.

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I also have access to a "sniffer" at the shop- So I will check it first, If it is way too lean- I will move the needle up- and set the mixture screw and check it again. Thanks

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