RB CARB Mod, What can I expect?

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dave04kdx
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RB CARB Mod, What can I expect?

Post by dave04kdx »

Ron has my carb and is working on it today. He is installing divider plate and doing pilot circuit improvements. How much different is the performance on my bike going to be?

I would appreciate any details. :grin:

Thanks

David
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Post by Tazmanian »

I just purchased a new air strike carb from R/B Designs it has a much better off idle throttle responce and gives my 2004 kdx220 more top end over the stock carb. I did have to back the air screw out close to two turns before my bike would run good. I'm running a Gnarly Woods Pipe and Boyesen Power Reeds I also have Gnarly Desert Pipe but haven't tried with new carb.
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Post by skipro3 »

I recommend you start with Ron's jetting and do a plug chop. From there, work with the air screw starting at 1 turn out by rolling on a flat hard surface at a walking pace, wick the throttle to between 1/8 and 1/4. Keep adjusting the air screw out in 1/16 turn intervals until the bike instantly lifts the front wheel with a throttle twist. This is the first sweet spot on the pilot air screw mix. There is another sweet spot about 1 more turn out. Some say this is a broader but less agressive hit that makes the KDX more rideable.

Don't worry David, you are going to love that carb. If you don't you will be the first one in history not to.
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Post by rlbranson »

David:
Do let us know how it works out. Also is your kdx a 200 or a 220? I have a 200 and the carb is a 35 mm. Ron bores the carbs to 36mm I believe. I wonder if 1 mm makes enough difference to notice. I have considered the rb mod, but I don't know anyone personally who has had it done on a 200. I am still looking for info on this modification.

Bob
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Post by KDXer »

RLB it isn't simply a divider plate install, theres a whole lot more 'stuff' done to the carb other than a plate.
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Post by dave04kdx »

Bob

My bike is a 200. I got the carb back from Ron on Saturday and I have nothing but good things to say about it. Rons machine work is excellent. The service from RB Designs is great. The modifications Ron does to the carb gives you an air screw that actually funtions! I played with the air screw settings while riding yesterday morning and a very small adjustment actually makes a difference in the way the bike runs. Throttle response is instant and crisp throughout the whole throttle range. I punched it from a second gear roll, lofted the front wheel and blew roost through 4th gear. Tight slow stuff the KDX feels much like a 4 stroke in the bottom rpms.

I asked Ron to recommend high altitude jetting. Not only did he print out a sheet of what I need, he supplied the jets.

Bottom line, best $165 I have spent for bike mods:supz:
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Post by rlbranson »

Dave:
thanks for the info. I will probabley do the rb mod. Then I will probabley get a ktm. It seems like after I put a bunch of money into something I often sell it and get something else.
Where do you ride at high altitude? up by prescott?


Bob
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Post by dave04kdx »

I usually ride in the Pinal's up by Globe/Miami.

Too bad your planning on going orange. Maybe the RB carb will change your mind :lol:

David
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Post by canyncarvr »

Mr. Black strikes again!!

Yeah..his work is sure pretty, huh?

Good to hear you like it.

This is old hat...but look for that 2nd sweet spot on the lo-speed circuit. Start around 2 1/2 out, adjust by 1/16's on either side until you find it. You'll know it when you do! 2nd gear will be much stronger, a more even pull. You can short shift to 3rd (even though it's a wide ratio away) with much more success (response will be there) than with the AS further in.

As long as your carb was off, it would have been a good time to have him reconfigure your cylinder head, too!

Something to do next time! :wink:

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Post by dave04kdx »

Wow, if it gets any sweeter it will be illegal :lol: I'll give the 2 1/2 turns a shot over the weekend.

I wanted to send in the head but couldnt swing it this time. Its on my list along with the delta force reed cage, and the ..... and the ...... and the..........
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Post by canyncarvr »

You still running the -30 pipe?

What is your opinion on the bottom end effect with the carb?

Ever try the CEK on -4? Give it a shot if you haven't.

It will take some patience to find that SSS. Honest...it takes only 1/16th to make a difference. Ride it for awhile on one setting before you try a different one. Again, it is NOT a matter of wondering when you get to it. It will be very clear to you!

Have fun!!

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Post by dave04kdx »

CC:

Yes I am still running the -30 pipe. The "Woods Pipe" is designated with -35, right?
Sometimes I wish I had the woods pipe. But then again, if I had the woods pipe I would wish for the desert/rev pipe. :wink:

To be honest I cant yet give a good report on the bottom end gain with the RB carb. I have only had time to ride the bike once since I got the carb back and that was just in the desert behind my house. I did notice a difference, I will report next time I get the bike to my favorite riding spot and give her a good workout.

I will try the cek in #4.
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Post by canyncarvr »

The RB carb was a good part of what moved me to a -30 (rev) over a -35 (torque..some refer to it as 'woods') for the woods. The DF3 was the other part.

I don't know that I'd call it a 'gain' anyway...more a matter of 'better applied' power than 'more' power.

FarmerJ was running a DEK-3 setup last weekend. I talked him into trying -4. The result from him was a thumbs-up. Easy enough to change back if you don't like it, 'eh? :wink: The difference between the clip postions on both the DEK/CEK is quite similar.

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Post by IdahoCharley »

What elevation are you at CC?

My older boy brought down his 99 KDX 200 and it was running Very Good with a CEK 3.5 clip position and a 152 MJ. Stock bike except for FMF Rev pipe and silencer.
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Post by KDXer »

3.5 ??? Have I missed something here ?? Do you have a small washer / spacer under the clip or something ??
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Post by m0rie »

Kay Dee, you can use another clip to shim the needle into a inbetween clip setting.

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Post by KDXer »

Why tanks Mo !!! :supz: Dat 'splains it good... :lol:
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Post by IdahoCharley »

Half-clip spacers are available from Yamaha or Sudco. I seem to end up using them fairly often. Seems I'll jet a bike to where I'm 98% happy (always want just a little more don't we all) and then the weather will warm up or cool off.

Anymore I just keep a spacer on the needle. On top of the clip if I'm not using it and below the clip when it is in use.

BTW - Some people will express concern with the needle not having the same ability or freedom to move about the vertical axis as it had prior to installing the spacer, but I have never found a problem with it. You can buy some needles that are a half-clip leaner or richer it if it really bothers you. IMO - when we start splitting hairs the carrying of an different needle is harder than carrying the spacer washer.
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Post by canyncarvr »

IC: Elevations vary from 1500-4700'

The CEK is a good needle. Hits a bit too hard and fast for me. Wore me out. A sign of old age no doubt.

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Post by clutchcover »

Wow CC, I thought you were higher than that. I see your jetting in your bike profile seems about as lean I run and my elevation starts at 4600 and goes to 10,000. Does all the RB work and DFIII make things run richer? I noticed that I used to run a 155mj 42 till it hit 100 degrees, then I dropped in some boesen CF reeds, I couldn't even run that jetting in 60 degree weather, not to mention the rain. I'm down to 152, 40 with a CEK on the way. Does the CEK have that dramatic effect with stock slide, woods pipe, silencer, airbox, and no other mods?
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