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2002 CR250 FLAT Mid Powerband...Why? Pics inside too :)

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Bike is snappy off bottom, Mid is FLAT top is OK but not great. 

 

- Air Screw is 1 3/4 turns out

- Pilot is in the leanest position

- Fuel ratio right now is 36/1 (usually run 44/1) What do YOU run and would moving to 44/1 help with my problem?

- Vforce is in good shape

- RC valve cables are tight

- I'm in California at near Sea Level

- Using the Mikuni TMX Carb right now and Carb is clean

- Air filter is clean

 

What do you run your pre-mix at in your CR250? 

 

What do you think is causing the powerband to go flat from 1/4 to full throttle? 

 

ANY ideas/info relevant to the CR250 (particularly the Mikuni TMX, at sea level, would be appreciated!!!

 

Thanks! Here's a pic of the project thus far too! 

 

p4pb10861734.jpg

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Jetting is AS FOLLOWS currently:

 

Main - 380

Pilot - 32.5

Needle Position - 2nd from the leanest setting (second clip from the tip)

Air Screw - 1 3/4 turn out

 

Not sure what's going on :( Not running crisp and Packing is new. 

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What does the plug look like & what are the current temps ?

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Which needle are you using? Stock?

 

Maybe the needle is damaged or the wrong size. Did you try a richer main jet and see what it does? Before that, did you try to richen/lean the needle by going up and down?

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For me, I run a a JD jet kit on my 265.... before, when it was a 250 I ran the JD Jet kit as the kit suggested. Ran great.

 

Im at sea level as well, just on the complete other side of the county on the Atlantic coast. 

 

This is what I have/had (if i remember right).

 

32:1 gas mix

 

32.5 pilot.

Main 400 (now is on a 410).

1 3/4 out on AS. 

Middle clip on the "lean" (red) needle. (now Im on the blue "rich" needle, middle clip). This is the biggest area I cannot compare with you, because the JD needles are what make the kits worth the money

 

These settings were for 95~ degrees F too. 

 

Your main and needle seem very lean. Richen it up by one size each time. Only doing the needle or main at once, then move to the other. Richen until there is no more power increase. 

 

I would try a 410 main and the needle on the middle clip to start. this with 32:1 raitio mix on gas. I think this would get you were you need to be. 

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Your jetting sounds about right. It shouldn't be far enough off to cause such a big issue.

 

Make sure that the powervalve isn't sticking or jammed at any point in it's travel. Take the cover off and make sure it has a smooth motion. The snappy low end and sudden flat spot sounds like a malfunction in there.

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Thanks for the tips guys!  Here's what I ended up having to do to get it running better...

 

Main - 400 (from 380)

Needle is STOCK needle - 1st position (from second)

Pilot - 32.5 Same

Slide - Stock

 

Fuel - 44/1 (36/1 previous)

 

Packing is new

Replaced with new Plug 

 

Bike runs much better now.  I'm in San Jose California (about sea level) and it was about 65 degrees out and sunny 

 

We'll see how she goes on the dirt soon! Waiting on graphics and motoseat cover

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Glad to hear you got it. I'm a little late, but for discussions sake, my bike had verrrry little top end. Felt like there was no powerband. Ended up being the butterfly in the RC valve was worn out. So it never opened up the exhaust valve

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Bike is snappy off bottom, Mid is FLAT top is OK but not great. 

 

- Air Screw is 1 3/4 turns out

- Pilot is in the leanest position

- Fuel ratio right now is 36/1 (usually run 44/1) What do YOU run and would moving to 44/1 help with my problem?

- Vforce is in good shape

- RC valve cables are tight

- I'm in California at near Sea Level

- Using the Mikuni TMX Carb right now and Carb is clean

- Air filter is clean

 

What do you run your pre-mix at in your CR250? 

 

What do you think is causing the powerband to go flat from 1/4 to full throttle? 

 

ANY ideas/info relevant to the CR250 (particularly the Mikuni TMX, at sea level, would be appreciated!!!

 

Thanks! Here's a pic of the project thus far too! 

 

p4pb10861734.jpg

Could change your needle jet to an S-7 and reset your needle back at the 3rd clip it would run better and you'd have adjustments later when it gets hot out. 

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