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200 Carb, Bore or NOT Bore

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Posted by: RTL---------------------

Hey guys and gals,

I have a new 200. I like what I hear about the 220's with the carb mod by RB. Can anyone tell me how it would change performance on my 200?

Also, if the mod costs about $200 why would I not just by a large bore carb?

Thanks for your responses.


Posted by: Fred T---------------------

but its for a 220. On a 200 I think you will gain more bottom end power, quicker throttle responce and maybe lose a bit ov overrev.


Posted by: canyncarvr---------------------

Better everything. You will not be disappointed! As good an improvement as a pipe.

Going from 35mm to 36mm is going to hurt overrev? No.

Why not buy a larger bore carb?

Cuz that carb still would not have the divider installed, would not have the jet screen cleaned up, would not have the TV machined.

Besides not fitting for diddle.
**edit**
If the subject is (and it is) the RB carb mod..how about a place to get all your questions answered? Like....maybe the guy that does it? Contact RB-Designs web site for further information including contact info.

From CDave's website (which you've read already cuz it's linked in the 'Every KDX Rider Should READ this...' thread stuck to the top of this forum:

Quote:


RB Designs is an Oregon based machine shop that is performing some very impressive modifications to motorcycle carbs. They bore the KDX carb to 36mm, install a venturi divider in the exit side of the carb, modify the jet screen, clean up the pilot circuit's bore, resize the throttle valve's cutaway and rejet the carb. The results are outstanding and its become one of my favorite mods. The off idle carburetion is excellent with clean crisp throttle response. You can easily lug the bike in a gear higher that you could normally and chug your way through the slickest conditions by almost eliminating unwanted rear wheel spend then when things oven up a little off you go. The bottom end becomes very 4-stroke like.


Doesn't leave a whole lot to question, does it?


Posted by: RTL---------------------

Thanks guys. I'm sending it off this weeks as well as the suspension to MX-Tech. Thanks for the help.


Posted by: canyncarvr---------------------

Here is where I paste in my XL400 spring opinion......

IF you are going to end up with .40kg/mm springs, DO ask jeremy to put in springs from a late model XR400. They are far superior to aftermarket 470mm springs..and are hot wound. That's a good thing.

I had .40s from jeremy. They collapsed. (not at all jeremy's fault/doing/responsibility). I asked him for a set of XR springs. A FAR better ride!!

It's not an opinion..but a fact of the matter (imo ). The honda XR springs are much better than any eibach, race tech or anything else in the run-of-the-mill replacement market


Posted by: RTL---------------------

I think I'm a little to heavy for the XR springs. I'm around 205 without gear.


Posted by: kiwimax---------------------

It appears to me that the cause of the rattle at idle is caused by an excessive clearance between piston and bore.

Early KDX's from 1989 to 1994 used the same basic engine, but did not rattle like the later bikes.

I have installed a "c" size piston in an "a" size bore (eg small bore,big piston)
and this certainly reduced the piston rattle.

I believe that Pro X can supply up to size "D" pistons.


Posted by: canyncarvr---------------------

Huh? This is some sort of posting error I presume?

Anyway..........

Pro-x gets bigger than 'd'.

Do you know what the size difference is between an 'a' and 'c' pro-x? ( I do).



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