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big fun

newbee here 08 yz450f putting on goodies questions?

7 posts in this topic

Hello to all this is a great place for info!! I have a 08 yz450f ,wanting more power!! I am purchasing new fmf ti 4.1 exhaust system. I am wanting to do merge products to carb ALJ,spring,and fuel mixture screw! Should I do merge products first! I know its not good to change too many things at once in setting up bike! Ive already did suspension PRO-ACTION front and back! Rides and handles great!! Can anyone give me any info? THANKS

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Alittle info on myself. I rode a Cr250 back in 1994 then purchased Banshee 4 wheeler. I made it very fast and fun to ride! Ive always wanted to get back on a bike but I am only 5' 8" . Ive over come vertically challenged problem! Love my new bike! Ive learned from the past that you can get alot of power just by having carb dialed in right!!! I'm alittle scared to take on exhaust and carb at same time! Carbs on 2 strokes are alot easier to work on! Me new to 4 strokes. Ive also purchased JD jetting kit! Just waiting on all parts to come in!!

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Should I do merge products first..? THANKS

No. IMO, you should ride it after you swap the pipe and then decide. The merge products are intended to clear up poor throttle response, which on an '08, is not usually an issue once the jetting is right, and $100 for the ability to adjust something you'll never have to readjust is kinda pricey, if you ask me. The extended screw is quite handy , though.

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Sounds good to me. These 4 stroke bikes are expensive to work on!! Any money I can save is a good thing! I will probably just do the fuel mixture screw and the Merge AP spring . I figured I would do the spring instead of O ring mod just because I dont want to have to worry about O ring wearing out or breaking over time. Thanks for info!!

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Sounds good to me. These 4 stroke bikes are expensive to work on!! Any money I can save is a good thing! I will probably just do the fuel mixture screw and the Merge AP spring . I figured I would do the spring instead of O ring mod just because I dont want to have to worry about O ring wearing out or breaking over time. Thanks for info!!
While you are correct about the AP spring being a more workmanlike approach to increasing the applied force on the pump plunger, the merge spring was made for the '07 and earlier models. The '08 already has a heavier AP drive spring than found in previous years, so I would still not install it so early in the process.

There is also the matter of whether you are "curing" anything by beefing the AP system. A lot of guys try to eliminate the slightest stumble, even where the the engine bogs when the throttle is busted wide open from an idle in neutral. This is completely unnecessary, and can actually hurt real performance. In the first place, you don't ride in neutral, and rarely ever break into the throttle at idle RPM. I learned to ride big thumpers back when none of them had accelerator pumps. We learned to "roll" the throttle open progressively. Not slowly overall, just a little less abruptly for the first little bit off idle until the engine responds, then quickly. Once learned, you never think of it. My son and I each ride an '06 with no AP mods, and neither of us has any problems with bogging. A lot of 2-stroke converts have quite bit of trouble with the concept.

This is not to say that a YZ450 might not need work on the AP, or that an engine so equipped should not be able to be tuned so that it can take the throttle being opened more suddenly than without an AP, just that too much can be expected, and correcting the matter entirely by mickey-mousing the AP system can leave you with a bike that runs poorly or stalls at other times because it dumps too much gas on the engine at the wrong time.

Cure only the problems that you actually have.

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Thanks Again!! Less is sometimes more!! Dont fix what aint broke!! Gotcha YA... I'm not even going to do o-ring mod on bike that I got with my JD jet kit . It doesnt sound like I need to the mod on my 08 yz450f bike! Should I use one of the supplied needles with the kit or use factory needle and jet it . If I use there needle - should I use red or blue needle , my altitude here is 800 to 100o above see level. Now I wish it would warm up here in Ohio so I can get my parts on and go riding!! Thanks again!!!! You the Man...

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