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Trying to Choose Rev/CDI box...

10351 Views 7 Replies 4 Participants Last post by  Here 2 help
I am looking for a CDI box for my 08 400ex. Any opinions on what you think I should use/ not to use???
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Dunno! I have heard they are useless unless you have a cam. The power gains go down before the governor even hits.
I do know of a cool upgrade that is relatively inexpensive.
Curtis Sparks sells a timing key that advances your timing. I don;t have one but have a friend that does and his 400 is faster than mine. THe only other mod he has to his is the key.
That is the link for thier products. THey also have a rev-box
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I have heard the same about the boxes, not much performance,
Plenty of other options......
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Use the stock OEM box unless the engine is highly modified - no power to be gained but you might get an extra 200 rpm.
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Thanks for your opinions!!! Even though people say they don't help, my best friend, and riding buddy has the same wheeler as I do. Same set up minus rev box, and font a arm, but that dont change speed issues just handling. But, we ride neck to neck till fifth then he starts pulling away. Thats all i want is to be able to hang not get some great difference out of it. Thanks again though!!
Not trying to be a nay-sayer but, you can buy two identical new cars, trucks, quads or whatever and one will out perform the other.

You list a Dynojet kit. Who installed the kit and calibrated it? Installing a jet kit will not necessarily give you more power (especially on the top end). If you installed a larger main jet, you might want to jet down 2 sizes and see if that improves the 5th gear power. Likewise, manufacturing differences in the carbs and engine might be affecting the power.

If you just got to beat your buddy, take into account riders weight (better yet, weigh each machine with the rider wearing all the gear he normally wears when riding), tire pressure (higher pressure = less drag, but too high of pressure can result in loss of traction at high speed)(if your tires are slipping and your buddy's tires are not, you could have more power and he will still pull away from you), riding stance, etc. Now if you can ride his machine while he is riding yours and his machine still pulls yours, then you need to make a minor change for that 5th gear power. Maybe you could get both machines dyno tested.

A Power Now device in the carb might help by reducing "power robbing" turbulance in the venturi of the carb. Having the cam degree'ed can help. Advancing the ignition with an offset flywheel key might help. Just changing to a lighter viscosity oil might do the trick.

Good luck and let us know what you discover.
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Yeah, I understand what you are saying and all. And thanks for the input! I think ill just put a new decal set on my wheeler. That's like an extra 5hp right there lol!
Ever notice that the guy with the most stickers always wins the race? I figure the more stickers you got, the faster you can go!
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