RB carb mod

Questions and Answers about the best carb and Head mods available for the KDX.
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canyncarvr
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Post by canyncarvr »

I did a search on this board for 'throttle response'.

I found a number of posts with exact how-to on adjusting the pilot circuit.

One thread pretty close to the top of the list was authored by some guy with the nick 'awoodman'.

:hmm:


That post covers modified and unmodified carbs.

That post covers the SSS, also.

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canyncarvr
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Post by canyncarvr »

>|<>QBB<
stringburner wrote:>|<>QBB<
canyncarvr wrote:
I see most people raving about the mod on their 220's, but not alot about the 200's. I was thinking the head mod gave better results on the 200 than the carb. mod. Not so?
I don't know what that means.

What 'the mod' on the 220, but not the 200?
Look to the subject line and all will become clear (RB Carb Mod).


I was referencing the subject in context, then I mused that the head modification seemed to get more praise than the carburetor modification, on the kdx 200. I figured boring the 220 carb would give better results because its bore is smaller than on the 200's carb, and the 220 has more displacement, and is basically starved for flow at upper rpm's. Clear? :wink: I understand it's not all about the boring, but adjustability too.
***
Your post had no subject. ;)

Got it. My apologies. I rarely read the subject with the thread. A personal foibile (one of many).

My earlier statements still fit.

I don't want to let it sit that the head modification is preferable to the carb modification for the 200. It is not. Maybe it should be, seeing as they cost the same.



Just kidding! Simply adding more confusion to what is already a thread that has exceeded my escape velocity.

****

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stringburner
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Post by stringburner »

I think that's the point I was getting at actually. Which, if you were only going to do one, would be recommended. I'll probably do both, but likely not the air stryker carb. That is a little high (to me). I just want it to run clean and not feel like it's running against itself. I couldn't get my bike to wheelie whatsoever. Proper jetting would probably help alot. I'm around the same elevation as Inda I think (600~ish), so I may try his jetting specs. Anyway, sorry for hijacking the thread. :sad:
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Post by canyncarvr »

If you're only doing one, IMO the carb modification would be it, yes.

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Post by awoodman »

I am trying to tune the air screw while it is around 50 degrees F outside. The jets are meant for like 70+, so how big of a difference is +/-30 degrees? And also, I have stock reeds. Will this make a big difference on the carb mod performance?
Last edited by awoodman on 07:32 pm Dec 19 2006, edited 1 time in total.
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Post by canyncarvr »

Regardless of the temp, the air screw will be adjusted in the same way. Probably won't end up in the same place, but you do it the same way.

I have not run a modified carb with OEM reeds. I would be surprised to find the reeds have anything to do this discussion. I mean, preventing the carb from performing the way it does with aftermarket reeds or reed cages.

They (OEM reeds) will make a difference in performance (less than other choices), certainly. The carb will still function fine.

I'm assuming stock reeds in good condition. Trying to jet a bike with any reeds that are NOT in good condition is a huge waste of time. You will never get it 'right'.

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Post by awoodman »

I know that the air screw will take effect, but will i need to change the jetting for these colder temps?
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Post by canyncarvr »

Sorry. I assumed that to be understood.

Re: '..will i need to change the jetting for these colder temps?'

Yes.


If you want it to be 'right', you do.

I change my air screw (effectively changing jetting) several times a ride, more often in colder weather. That's due to there likely being a wider range of temps with the sun out during these shorter days of the year.

Don't misunderstand. It is NOT necessary to dink with your carb 20 minutes for every 15 minutes of riding. My bike isn't jetted 'correctly' MOST of the time for that very reason. Being 'right on' by the numbers, by procedure and jetting method is something to yak-yak about, but certainly isn't required to have fun riding!!

A few motos in a covered arena over the timespan of a single day ain't the same a'tall as starting a ride without the sun in the 20ºs, and ending up riding in the sun in the 50ºs.

Don't give yourself a hernia over it. Understand the basics, change things as often as suits 'ya!

This is supposed to be FUN!!

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Post by awoodman »

and I enjoy working on it, but I need to ask these questions when I do something for the first time. Even with colder temps, i shouldnt need to change the jets, for it to have reasonable throttle response, right? It just bogs really bad, now.
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Post by grump99 »

>|<>QBB<
awoodman wrote:you mean that when I have it at 0 throttle and i go WOT right off the bat, it shouldn't bog at all? because it does badly. Theres no whay to tell which way to turn the airscrew?
Are you at low rpm (around idle) and snapping the throttle wide open instantly? My bike bogs under those circumstances, no matter what jetting I use.

Try rolling on the throttle for a short moment until the revs build just a little, then you should be able to snap the throttle wide open without a bog. If you want to launch fast, rev the bike with the clutch in and feather the clutch out while adding throttle.

What jetting are you using? Try raising your needle by 1 clip. I went from CEK-3 to CEK-4 and it cured a bog I was developing when the temps dropped. Getting your jetting close is not too hard once you get the hang of it. Like CC said, it does not need to be perfect to have a blast.

Good luck!

Tony
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Post by canyncarvr »

Questions are fine.

Re: 'Are you at low rpm (around idle) and snapping the throttle wide open instantly?'

..and this:

Re: 'Even with colder temps, i shouldnt need to change the jets..'

sounds real familiar...within the past week?

What grump said is right.

Even with colder temps...you SHOULD rejet...if it WAS jetted properly for 20-30º higher.

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