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jetting pretty good for 2003 YZ250F

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I was going to sell my 2003 YZ250F when I first got my 2006 YZ250F. So I started taking all the cool parts off of the 2003 and swapped them over to my 2006. I tried using the JD jet kit from my 2003 on my 2006, and switched back to the stock needle (JD ended up making a different jet kit for the 2006, I believe).

When I put it back from the 2006 to the 2003, I ended up somehow switching the clip from the 4th position from the top, to the 5th position from the top. The bike ran like crap from low throttle to mid.

I put it back to the 4th clip, and put in a fuel screw (a TITANIUM fuel screw, no less) for easy fuel adjustment. Supposedly the aluminum fuel screws can be brittle and break easier than the titanium. I'm a fool and his money, I say. Whatever. The packaging was pretty, it made me feel like a pimp. :applause:

So it's my 2003 YZ250F; stock air filter/screen, M4 pipe, JD jet kit, 185 main, blue needle, 4th clip from top.

It was 31 degrees F outside today in MN. The dyno run said it was like 51 degrees F inside the garage. So in reality, the bike probably experienced everything in between those temps.

Here's the dyno run:

2003%20dyno%20run%20-%20pic2.JPG

Here are a few observations from this run:

1> slightly lean at 14.82; but let's pretend that it's around 51 degrees F (the dyno printout says 51 degrees F, but it was about 31 outside). I'll hardly be riding in anything colder than that; in fact, probably more likely in the 60s-90s during the summer.

2> let's pretend it's warmer, and less dense air, so the jetting now is around perfect. See how nice the curve is? That air/fuel line is like, totally straight.

3> ONLY 29 HP?!? This time I filled the rear tire up to about 30 psi. This is my 2003, and I've never rebuilt it! I haven't checked the valves since last year either. My 2006 stock made 29 on this dyno (but with lower tire pressure). I'm guessing the poor old girl (yes AV, I said GIRL for this bike!) is getting tired. :lol:

4> I know it sucks this dyno run reads in MPH. I don't know if we had the RPM hookup "hooked up". Oh well, I was really just wanting to get an idea of where my jetting was, and now I know I'm not going to change a thing.

5> yes, this is what I do with my vacation days.

:applause:

ps. I know I'm a goofball, but I used a little bit of this fuel additive from KEMCO oil and chemicals. Check it out http://www.kemcooil.com/products.php?cId=5. It does nothing for performance, it only makes your exhaust smell different!

Anyways, I used blueberry, and it smelled like blueberry pie when we were sitting around chatting before I rode from the dyno area over to my truck. The guys thought that was pretty funny; and it really does smell pretty good! Just something to make people smile.

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A knobby rear tire will give a lower power output on the dyno by about 5hp. Your results look good overall.

James

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A knobby rear tire will give a lower power output on the dyno by about 5hp. Your results look good overall.

James

wow, thanks dude! I'm impressed with your jet kit, nice air/fuel ratio! She runs great.

I'm using a Goodyear dirt track tire; a CD2. I have it on a separate wheel I always use for dynoing. My 2006 made 29 HP (the same amount) when it was stock on that same dyno (with the same rear). I know that dyno reads low. I just use it to check out my a/f ratio (or to do a baseline and then a modded run, to make sure the curve keeps moving the right way!).

She might be a little bit tired. She has a pipe, and only makes as much as my stock 2006. I should freshen her up with a new piston and rings, and at least check the valves (it's been a year, although she wasn't ridden much this last summer).

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