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Thread: cdi mod for your 400ex

  1. #11
    Join Date
    Aug 2009
    Location
    PA
    Posts
    467
    threw around getting a dynatek adjustable rev box but i dont have the cash right now. not sure whether to save up and get it or get something different. advance keys are out of the question. most likely going to get a monster coil though, not sure how much they are used compared to new but ill find something.
    2005 400EX
    99-04 plastic, 155 main jet, 42 pilot jet, HMF Sport Series Slip-On, UNI air filter, LSR PB Block off plate, TAG bars, AC nerf bars, 15/39 gearing, CST Ambush rears, stock Ohtsu fronts

    1973 Yamaha DT360A Enduro
    hooker headers/expansion chamber no other pipe

    98% of the teenage population does, will try or has tried smoking pot. If you're one of the 2% who hasn't, copy & paste this into your signature.

  2. #12
    Join Date
    Mar 2010
    Posts
    294
    look at any dyno chart on a 400ex they stop making power ever before the stock rev limit ( 9100 I believe) so why buy an aftermarket box to make it rev to 10 grand if its not making power anymore? just putting more stress on the valve train if you ask me...buy a degree key instead for the throttle response
    '05 400ex------------*SOLD*
    - 11:1 wiseco 416

    - K&N with outerwear

    - 450r Carb

    - FMF PowerCore 4 slip on- FOR SALE (Big Gun or LRD next)

    - Tusk nerfs with heel guards

    - WTB: 450 Front Shocks

  3. #13
    Join Date
    Dec 2003
    Location
    Winchester Indiana
    Posts
    469
    Originally posted by bherriman
    look at any dyno chart on a 400ex they stop making power ever before the stock rev limit ( 9100 I believe) so why buy an aftermarket box to make it rev to 10 grand if its not making power anymore? just putting more stress on the valve train if you ask me...buy a degree key instead for the throttle response
    Agreed, there is no need to replace the stock cdi unless you have a built engine that can continue making power at 9000+ rpm.

    The majority (95%) of EX builds are good for about 8000 rpm then the power starts to sign off.

    Unless you have a fully built race engine then you are basically throwing your money away.

    A better way to spend your money is either a timing key or a 450R carb. Both of which will give you much better throttle response and power than a CDI.

  4. #14
    Join Date
    Apr 2009
    Location
    Las Vegas, NV
    Posts
    1,297
    That's what I've always told people who are considering CDIs. Most of the time they've already made up their mind and just buy them anyways. I got both the Sparks key and a 450R carb for like $100. They are both well worth the time and money and will produce much better gains than a CDI.
    '05 TRX400EX:
    |White Bros. E-Series Exhaust|Sparks +6° Key|42mm Keihin Carb: 165 Main, 52 Pilot|ESR Airbox Eliminator Kit|TAG T2 Bars|MSR AOF Clutch Perch & Lever|Burgard +2 A-Arms|G-Force Extended Hubs|KFX 450R Shocks|IMS-Roll Classic Bumper|AC Racing Blackline Pro-Peg Nerfs|ITP Holeshot H-Ds|Skat~Trak Extreme Paddles|

  5. #15
    Join Date
    Sep 2010
    Location
    the south
    Posts
    446
    the xr25r cdi box gives you 800 more rpm's and more timing curve, but what i need to know does the 350x give more timing curver also or just more rpm's?

    Thanks EJRacing
    Thanks to EJRacing for the fastest 400 exs in the USA.

    Also thanks to Top Secret Racing , EHS Racing and Racer Edge
    for the fastest 700/804 Raptor in SC and NC.

    All bike's DYNO tuned by EHS Racing of Rockingham NC.

  6. #16
    Join Date
    Dec 2003
    Location
    Winchester Indiana
    Posts
    469
    350X has no limiter that I am aware of. Not sure about timing advance.

    What I do know is that it is useless to "upgrade" your cdi from a factory 400EX CDI as they are completely done making power by 8000 rpm. Anything more than that is more wear and tear on your valve train.

    If you raise the RPM limit on a 400EX you don't know when to shift in the first place.
    99 416EX
    12.5:1, XR400R cam, Ported, FMF Powerbomb header/White Bros. E-Series Slip-on, Hinson clutch, KN/open lid, 40mm FCR tuned for E85, KFX450R front shocks, Works Ultracross Rear.
    08 KFX450R
    Pro Circuit TI-4 Full system, KN intake, PC V, Hotcams Stg 2
    10 Yamaha WR250R
    Street legal dirt bike
    99 Chevrolet Camaro Z28 M6
    H/C/I/N2O All motor = 430rwhp/403rwtq 150shot = 591rwhp/649rwtq 11.4 @ 128 on regular street tires 26mpg
    93 Eagle Talon TSI AWD 5spd
    Evo3 16, 272 cams, Evo 8 Rods/Pistons, 560cc injectors, 2G MAF, DSMLink @ 17 PSI

  7. #17
    Join Date
    Sep 2010
    Location
    the south
    Posts
    446
    With all the mods my bike has it dont stop pulling till it hit the limiter, so my bike could use a lil more rmp's.

    also a real racer know's when and where to shift his bike becouse he can feel when the bike stops pulling.

    some people think the harder you rev, the bike the faster it will go. that it not the way to ride the bike.

    but i would like to say thanks for your input.
    Thanks to EJRacing for the fastest 400 exs in the USA.

    Also thanks to Top Secret Racing , EHS Racing and Racer Edge
    for the fastest 700/804 Raptor in SC and NC.

    All bike's DYNO tuned by EHS Racing of Rockingham NC.

  8. #18
    Join Date
    Dec 2003
    Location
    Winchester Indiana
    Posts
    469
    I forgot your EX is one of the built few that can run that rpm while still making power.

    Shop you run 300ft or 1/8?
    99 416EX
    12.5:1, XR400R cam, Ported, FMF Powerbomb header/White Bros. E-Series Slip-on, Hinson clutch, KN/open lid, 40mm FCR tuned for E85, KFX450R front shocks, Works Ultracross Rear.
    08 KFX450R
    Pro Circuit TI-4 Full system, KN intake, PC V, Hotcams Stg 2
    10 Yamaha WR250R
    Street legal dirt bike
    99 Chevrolet Camaro Z28 M6
    H/C/I/N2O All motor = 430rwhp/403rwtq 150shot = 591rwhp/649rwtq 11.4 @ 128 on regular street tires 26mpg
    93 Eagle Talon TSI AWD 5spd
    Evo3 16, 272 cams, Evo 8 Rods/Pistons, 560cc injectors, 2G MAF, DSMLink @ 17 PSI

  9. #19
    Join Date
    Sep 2010
    Location
    the south
    Posts
    446
    we run 1/8 mile and dirt. let me ask you this ( have you ever seen a 400ex make 68hp? ) cuz mine does and i have posted the dyno sheet on here befor.

    The 426 runs 7.55 all motor in the 1/8 mile and 7.10 in the 1/8 mile on nos, it will go faster on nos if i can get it to not break up at the 594 mark, at the 594 mark my son just backs out of it so we dont blow the motor.

    We also drive state to state to drag race other 400 to show we have the fastest 400 in the (US.) we run 450s,raptor, and shee just to prove a point.
    Thanks to EJRacing for the fastest 400 exs in the USA.

    Also thanks to Top Secret Racing , EHS Racing and Racer Edge
    for the fastest 700/804 Raptor in SC and NC.

    All bike's DYNO tuned by EHS Racing of Rockingham NC.

  10. #20
    Join Date
    Sep 2010
    Location
    Western Washington
    Posts
    702
    Kind of highjacking this thread but my Ex won't hit a limiter. It might eventually but I'd have to rev it unreasonably high. My 450r on the other hand could hit the limiter so easy I sounded like Barcia.
    High RPM Motocross - Trippin Rev Limiters since 2010

    2006 Trx450er - White Brothers Aluminum Pro Full Exhaust * Sedona Bazooka Tires * Tusk Nerf Bars * DG Grab Bar * Magura Handlebars * More To Come!

    RIP 400ex

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