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Two-Stroke dirtbikes question

Old 01-15-2018, 06:51 AM
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i still ride my 1985 rm 250 ,crazy power still so i bought a ktm 200 exc to ride in the woods
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Old 01-28-2018, 12:40 PM
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Okay - it was definetly too rich. Played with needle jet in all positions and it runs best in position 1. I guess I'm a little surprised - I would have thought that with aftermarket pipe (FMF Gnarly and Turbinecore 2) it would have flowed more and needed more fuel. It's still a little "jerky" and smokes a little so I'm thinking of going to a fatter needle, which I have from a spare carb. Right now I am running the stock needle.

Any value in switching to a needle that allows you to run in a more "middle clip position" - or if it runs good in position 1 just roll with it....

Also read a lot about these carbs being sensitive to float level being within spec. So sorted that out.

Side note. This thing appears to be pretty fast.

Last edited by seafordguy; 01-28-2018 at 12:53 PM.
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Old 01-28-2018, 04:22 PM
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A good pipe can actually make a bike run richer as it has a better return pulse to keep the new fuel charge from escaping.

As for the needle, length diameter and taper all effect mid throttle jetting.
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Old 01-28-2018, 07:53 PM
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I have a wider needle but it's wider to the naked eye so I'm not going to bother. I also noticed I have a leaner slide. Going to figure out tomorrow if it's a #7 or #8 - stock is #6. Then order a leaner needle and just experiment a little.

Also going to lean the bypass out another turn as that apparently affects mixture between 0-3/8 throttle.
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Old 01-28-2018, 09:14 PM
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I didnt know 2 strokes had a 3/8 throttle position.... I thought they were either turned off sitting in the corner or running wide open. LOL
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Old 05-21-2018, 07:11 PM
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So - after a few more months and some conversations with some very knowledgeable people I now know that I had a Chinese knockoff Keinin carb but when I went back to the OEM carb the seat for the float needle was out of round. Evidently this is somewhat common in these Keihnin and they aren't replaceable - pressed in brass. I now have a new OEM airstryker on there courtesy of CarbWarehouse. Bike starts right up and doesn't smoke at all. I think it's still probably a little jumpy for a first bike but I'm going to go out and give it a little time - I just wonder if a 4-stroke would make a better starting bike.
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Old 05-21-2018, 07:24 PM
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Cheap experiment, If you can go a tooth bigger on the countershaft sprocket, that will be taller gearing and possibly a greater top speed but it will mellow it out a little bit, also ride a gear higher just dont lug the hell out of it.. you will be used to it and wanting more in no time....
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