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About gearheadmc

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    TT Newbie

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    New Mexico
  1. My son has been campaigning a KX85 for the first time in a state wide desert series. The bike is very fast but has an explosive powerband that makes it difficult in some technical areas. This seems to be a popular subject on many forums with recommendations that include: disconnecting the power valve (lol). flywheel weights, shimming or replacing the spring in the PV controller, Replacing the PV with an aftermarket one. I am a machinist/engine builder so I attacked the problem head on. I first tried shimming the PV. That made it worse. Note: The PV is pressed together and is very tricky to get right. a mistake here could deposit large steel ball bearings into your gear case. Ouch! I should mention that the very costly PV kit will require you to perform this operation to replace the controller spring. Next I built and installed a 10 oz. flywheel weight. These weights are available up to 12 ounces. This did mittagate the problem but not to my satisfaction. (It did improve launch control). Not ready to spend the big bucks or go full retard another direction I would try another old trick. I created a .250 thick aluminum spacer to add between the reed pack and cylinder head. This radically increased mid range width and breadth. No problems with air box clearance and no re jetting was required. My son says "its a whole new bike".
  2. I find that 303 or 304 stainless works well for this ap and offers good rust and corrosion resistance.
  3. gearheadmc

    flat tracking a 2 stroke

    Thanks jeekinz. It was my understanding that the "gnarly" version of the FMF pipe is the most torky pipe available for my bike. The chamber is monster sized but sensibly mounted.
  4. gearheadmc

    flat tracking a 2 stroke

    Just to finish. Power was greatly increased overall. Midrange and top end were AWESOME! The 450s including the prepared ones had their work cut out for them. 3rd in points for my rookie year with a Two stroke. No suspension work. Going to get em next year. Good times!
  5. gearheadmc

    flat tracking a 2 stroke

    Just to update. I took .025" off the head but bore clearancing obviously reduced my yield. (The head had a pretty aggressive deck clearance from the factory) I wanted to try this before my full annual. (it was really due). Results: definitely an improved mid to high transition leaving the corners. No observable change in engine braking. Some observations: Although I dutifully checked the plug and for drivability changes before the race. Upon teardown for the annual I discovered that carbon build up on the power valve and related cavities was a bit excessive indicating lean by my guesstimation. My inspection 3 weeks before showed no such deposits. So new racing slug that starts with a funny "W" sports new ring positions and full coating, a bit fatter mix and new bearing confidence makes me a bit excited. I'll keep you posted. Haven't forgot about You Bolon. Stand by. Notes: Bel ray H1r
  6. gearheadmc

    05 kx250 to 08 kx250f

    My brother has an 05 kx250f and I have an 03 kx 250. The 250f is far easier to ride and has very predictable and considerable power. My brothers previous mount was a crf 450 and he likes the overall behavior better even though he has sacrificed some power. The kx has lots of power but is far more difficult to ride but maintenance costs are far lower for the two stroke obviously. Like my bro says "two strokes steer with the rear (tire) and four strokes steer with the front". Neither bike is a bad choice. We ride primarily flat track and desert.
  7. gearheadmc

    Lowering my Kx 125

    Late model dirt bikes are designed beautifully. Swingarm angle actually creates better bite. Lowering the rear end Via the seat does less to disturb the remarkable engineering done by the manufacturer. If you have any doubt about this... Go out to the garage, fire up the bike, set the clutch (using the front brake) and watch the direction that the seat goes. The seat will rise with clutch load thus loading the rear tire. This is one reason that they sell "starting blocks" for shorter riders. Tippy toes and side saddling really pays dividends when utilizing your bikes full potential if you can do it.
  8. gearheadmc

    flat tracking a 2 stroke

    Earlier this season I began to campaign my 03 kx 250 at my local flat track with reasonable success but although the bikes performance down the backstretch is stellar, power control during banking is somewhat spurious. The bike is equipped with an fmf gnarly pipe and have already re shimmed the K.I.P.s valve as per team green (which helped quite a bit). I am considering raising the compression ratio in an effort to increase the midrange and increase engine braking on decel but my question is... Would a reed pak do essentially the same thing by increasing overall induction? The bike typically operates @ 5500 ft. plus or minus 400 ft. Any help would be most appreciated.