Jetting for mods

Joined
May 30, 2003
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#1
New KDX220R
Ran it for the first time last weekend and it was GREAT!

But I couldn't leave it alone.

I installed a FMF Gnarly rev pipe, turbine core II silencer (forest legal), torque ring and Boyeson Rad valves.

I did NOT change the jetting but the Boyeson material suggested 2-4 sizes leaner on the main jet.

It started and ran pretty good on the street in front of my house; but thats no real test.

Anyone know a starting place for recommended jetting? The stock main jet is a 145.

Thanks,

Andrew
 
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#2
Okay, I'll answer my own question. The Boyeson material said to go leaner 2-4 sizes. I went 3 sizes leaner: 145 down to 138 main jet.

It friggin' screams, and still idles well cold.
 
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Mar 15, 2003
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#3
I think it is safer to only go one size smaller at a time and test it out.

I've heard 'Carvr say something to the effect, "When you start getting it too lean it runs really good right before it blows up!" ;)
 
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#4
yeah, I suppose that you're right. Lean is mean until it melts. But 145 down to 138 is not too extreme. These jets comes in 2.5 increments instead of the usual 5. I would have done it that way but the dealer was out of 142.5 and 140.

I'll go to the parts house on Monday.