2003 kx 125 in the woods?

Discussion in '2-Stroke Discussion' started by cactusreid, Aug 29, 2004.



  1. cactusreid

    cactusreid Rookie DRN Member

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    G'day everyone- I just got my son (13 yr's old good bush rider) a kx 125. It's probably not the most "bush friendly" bike but the deal was just to good to pass up. I've ordered a 9 oz flywheel weight for it, but I'm just wondering what other mod's anyone may have done/know about that will give the bike a bit more bottom end power? I realize it's a tall order asking for bottom end power on a 125,but it never hurts to ask.

  2. SMAKme2X

    SMAKme2X Rookie DRN Member

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  3. SMAKme2X

    SMAKme2X Rookie DRN Member

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    if you dont mind the loudness, you could get a pro circuit pipe with a pro circuit R304 silencer exhaust, which will give u alot of lower range and top end power, but you could also get the FMF powercore 2 and that gives the bike about 2 more horses
  4. SMAKme2X

    SMAKme2X Rookie DRN Member

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    you could also go 4 sum v force reeds
    '
  5. Detonator

    Detonator Rookie DRN Member

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    I ride/race 125's in the woods (Vet class), and have found they're a great combination of sharp handling, snappy motors, and less tiring than other choices. Not that you asked, but here's what I always recommend to other 125ers headed into the bush:

    Drop a gear on the front sprocket. This $8.00 move will get a better result than a $200 pipe. You'll never see 5th gear in the bush, anyway. While you're at it, toss an O-ring chain on and keep the stock as a spare.

    Boyesen reeds help with low end response and give the snap you need for clearing logs and roots. They don't increase horsepower, but can "wake up" a lazy bottom end.

    You'll love the flywheel weight and wonder why they don't come like that stock! Easier starts, difficult to stall unnecessarily, hooks up with mother earth instead of spinning everywhere. Increase your idle a bit to allow the engine to stay running while you're in gear with the clutch in.

    Re-route non "draining" carb hoses up higher, or ideally into the airbox. Radiator guard, skid plate, hand protectors. If you're handy, you can make a grab-strap out of an old tie-down and mount it between the seat and rear fender. When the stock bars bend (about next week), consider a shorter bar length to slip between trees easier.

    Truthfully, dropping a gear on the front and getting your jetting crisp (especially airscrew for that 0 to 1/4 throttle response) is going to yield your best results short of getting a big-bore kit or port job for low-end. The aftermarket pipe idea isn't bad, it's just expensive. Stock pipes tend to be more durable and quieter. Save your money for the best safety gear you can get for your child. For the same cash, look into some helmet communicators http://www.collett.mb.ca/ My buddy and I have had ours for a year, and can't imagine long rides without them. They add a new dimension of safety and fun to riding. I hate riding with people who don't have one!
    Your son is very blessed to have a dad who wants to ride with him. Happy trails!
  6. CaptainObvious

    CaptainObvious Formally known as RV6Junkie Damn Yankees

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    50T sproket on the rear and a pipe. I think the KX is a fine woods bike for 80% of what you come against in the woods...and it works OK for the other 20% too.
  7. GhostRider32

    GhostRider32 Rookie DRN Member

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    I agree with going down a tooth on the front sprocket. I went down a tooth on the front and up 2 on the rear and it made a big difference. Now my KX250 is geared more towards woods riding and not racing. A 13oz. flywheel weight is next on the list of mods and then I'll probably have all I need.
  8. cactusreid

    cactusreid Rookie DRN Member

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    Detonator: Thks great ideas!! This bike was a west coast mxer before we got it. It has a pro circuit pipe and a shorty silencer on it now. also it's got 2 stage reeds in it. I've already dropped the frt sprocket one tooth and put a good old o-ring chain on it that I had as a spare .So far I haven't had great luck getting this bike to idle real well,but I'm still playing with it. My son has the full gear package,and it makes me feel a lot better rat raceing through the trees with him knowing that we both are protected equally! Personally I wouldn't ride this bike in the bush for all the gold in FT Knox!! (IT'S still full isn'T iT?) I ride a GasGas EC 300 which I absolutly love! My bike is the smoothest torqueiest bike I've ever had. Thks for the compliment, It seems that kids really do appreciate when you spend time with them.
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