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08 KTM 200 Pipe & Carb Test

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In case anyone's interested I thought I'd post the results of a few tests I ran about a month ago. I figured I'd test rather than just take peoples word for what they liked/felt so hopefully the actual numbers I recorded help. I did this test by placing cones out at 30,60,160 and 300 ft on about a 2% incline with my son running a stop watch. I did three runs for each distance before moving on to the next furthest. The terrain was hard pack with a thin layer of loose dirt and scattered round rocks of various sizes common to the West Coast. The temps that day ranged from 74-77 degrees with 22-24% humidity and conditions continued to be dry and sunny.

The bike had a fresh motor,Boysen Rad Valve, and spun a slightly used 18" Maxxis SI with 14/48 gearing. I am a 47yr old B rider weighing about 175 without gear.

The parts I tested were the stock carb w/ 165 main, 85, 45 pilot(air screw out 1 1/2) and a Lectron Legacy carb as well. I also ran each of these with pipes in great condition, a 11' Gnarly and a stock pipe. Note: The 11' & up FMF pipes have a larger(2 mm?) diameter so require an equivalent silencer!

I ride mainly in the woods and like to play on tighter MX tracks so low end is helpful given the cc's. I returned to the Gnarly and richened the Lectron just a bit as the power is very linear and fuel economy can't be beat. An allen key to remove the top cap is all that's really needed for tuning, but any bike with a big tank's gonna make this a bit of a PITA. I hope this helps anyone who's on the fence about parts or curious. The Lectron' s expensive and I went with it because of the tuning ease and the fact it's made with the same features you have to pay the same amount or more for to have incorporated into a stock carb. On long rides the fuel usage helps too, but if you're on a budget the stock carb does pretty damn good! Have fun out there!!

KTM_200_PIPE_TEST.JPG

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It's not bad ! A friend who had a 200 said its just like the "Fatty" which coincides with an old article written by a KTM World employee who prepared a 200 for GNCC racing. The main difference I " felt" and I think was shown by the times was that the stock let the bike stretch its legs a bit , where as the Gnarly caused a need to shift a bit sooner. If I were to try anything in the future I may try the stock pipe with some different gearing. Any recommendations would be appreciated. I'm thinking 14/50 or maybe a 13/49

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I like tests like this, to supplement the "seat of the pants" measurement.  I'm curious how much variation you had run to run, and if that variation is greater than the small difference you are seeing between the setups.  Also wondering if you took off from a dead stop or if you used a rolling start.  I'm guessing if you launched every time, you might get some variation run to run in how well you were able to get traction.  Then there is variation in exactly when you start and stop the stopwatch, as well as your shift points, and any wheelspin as you accelerate.

When I did a similar test when comparing main jets, I tried to remove or minimize all sources of variation.  I used a rolling start instead of a launch, and I ran the whole test in top gear to take out any variation due to shifting.  I ran the test on pavement instead of dirt, so no wheelspin.  The test started from a slow rolling start, trying to use the same starting speed each time.  Simultaneously start the timer while cracking the throttle, at the same starting point on the road.  The bike would slowly wind out as it was in top gear, and since the test was at wide open throttle, it's using the main jet the whole time (the purpose of my test).  I then found a landmark near the point where the bike would reach max rpm, and by using the entire rpm range, it maximized the duration of the test, which minimizes the effect of the other variables / noise factors.  Stop the timer at the same landmark every time.  

Even with all those precautions, my run to run variation was greater than the difference in jetting, but the trendline in the averages was consistent.  The data matched the seat of the pants evaluation.  Once the jetting got too rich, the acceleration was noticeably worse, didn't sound as crisp, and starting showing up on the stopwatch.

Effect_of_jetting.png

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