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RB Carb Mod Question: KDX220

Joined
Aug 27, 2006
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#1
I just had my carb modded by RB Designs. It made a huge difference in the top end - the hit is now similar to a track bike with solid low end and mid range.

I have no complaints in the way the bike runs, but the air screw adjustment doesn't seem to have much effect - and that is one of the major benefits of this mod. The bike seems to run the same with the air screw adjusted anywhere from .5 turns out to 3 turns out. It's my understanding that the air screw should be very sensitive and make a noticeable difference with only minor adjustments.

Any one else have the same experience with this mod? Suggestions?

I also have Boyseen 607 reeds, Fredette porting & squish band mods, airbox cover removed, PC pipe, and carb jetting at 40/150 with CEK needle in 3rd clip. I usually ride at 2k feet and 75 degrees.

Thanks for your input.
 
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Feb 2, 2006
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#2
crhines said:
I just had my carb modded by RB Designs. It made a huge difference in the top end - the hit is now similar to a track bike with solid low end and mid range.

I have no complaints in the way the bike runs, but the air screw adjustment doesn't seem to have much effect - and that is one of the major benefits of this mod. The bike seems to run the same with the air screw adjusted anywhere from .5 turns out to 3 turns out. It's my understanding that the air screw should be very sensitive and make a noticeable difference with only minor adjustments.

Any one else have the same experience with this mod? Suggestions?

I also have Boyseen 607 reeds, Fredette porting & squish band mods, airbox cover removed, PC pipe, and carb jetting at 40/150 with CEK needle in 3rd clip. I usually ride at 2k feet and 75 degrees.

Thanks for your input.

I have the FRP porting and squish band, but I have the stock carb bored out to 36mm by Fredette with Vforce3 reeds 10oz flywheel wieght, FMF desert pipe.
My understanding is that because of the porting you will not have the same effects as others with th RB mods done. I have also read that the RB carb dosnt like the FRP porting. I love my 220, it hits like xc 300 smooth with lots of low end and plenty of top end. I have played with my jetting for a year. depending on temp and humidity I run 42-45 pilot C to D needles in the 2nd to 3rd clip position 155-158 main. airscrew 1.5 to 2 out.

The flywheel weight helps keep the rear tire hooked up with less clutch work. I can run into a flat corner come out in 2nd with out slipping the clutch and climbing in rocky slippery conditions is very nice kinda 4 stroke ish, just shift up one and hold the throttle steady she just bogs right up with no wheel spin.

also I was running a FMF woods pipe and the bike ran ok but the rev/desert pipe seems to be the perfect match for the porting.

I am one of those guys that likes peak performance and will tinker untill I get it. If the temp changes drastic during a ride I will rejet on the spot. If I cant get max performance then some thing changes.
good luck
Matt
 
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Dec 11, 2003
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#3
I'm right with you guys. I have the frp porting on a 200 to 220 frp overbore, vforce3 reeds, pc plat2 pipe, open airbox rb airstriker carb. I notice the same thing that the screw doesn't do as much as I thought it would. it's not hard to get it dialed in but your turning it half turns instead of 1/16 like they say. my machine is great on the bottom,, a little crazy on top and that is with the plat2 pipe. I notice that all that power on top really starts to show how unbalanced the rest of the bike is. for racing that is..
 
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Dec 11, 2003
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#5
I just raced it in an enduro and the suspension is too soft for hard racing, IMHO also its a bit heavy and I felt like i was fighting it at some points. Thats what you expect from a 10+ year old technology though and why the exc is superior to most race guys. if you just slow down a little you dont' notice it.
my jetting is a bit rich at 42/155 clip in 4th position and about 1 turn out on as. this is because I ride on gravel roads and highway too at many different temps,, my bike is street legal with a baja designs lighting kit. If it was offroad only I would jet it a little leaner and probably do suspension work.
jeff f. didn't recommend the rb mod to me when I was doing my cyl work and I believe him now. my airstriker is a great carb but it was 325.00 and I don't believe I gained enough over my 35mm 200 carb that was jetted spot on.