Ok, for those who wanted more details on improving stopping power with KX parts, I did some research and found some particulars.

1. The disc is kawasaki PN 41080-1377. It is a ventilated, cast iron rotor. The rotor is used on both the KDX200/220 and KX250 here in Japan. In the US, they are not used on the KX250 but ARE used on the KDX200/220. After checking stateside diagrams, they are used on the 1995 through 2006 KDX200 as well as the 1977 through 2005 KDX220. It's a direct bolt-on...no mod's necessary.

2. The master cylinder is PN 43005-0041 and is used on 2005 through 2007 KX250, 2006 through 2007 KX85 and 2006 though 2007 KX100. This master cylinder adds additional stopping power, but the single, most significant thing it does is gives you better control over the front brake...no more of this 'all or nothing' feel that we get from the KLX master cylinder. The improved cam action of the KX lever makes it much easier to apply exactly what is needed and requires much less force.

3. One very important item to note is that you will lose your front brake light switch. The way most people get around that is to buy aftermarket oil pressure warning swich that is plumbed into a banjo fitting.

I hope this info has helped to clear a few things up.

 

Do you think that the upgrade has to be done with rotor and master cylinder together, or would the mastercylinder alone gain some performance?

 

The master cylinder alone makes very marginal improvement at best. Most of your stopping power increase comes from the cast iron disk combined with the increased control of the KX master cylinder. Now, I've never seen the KDX disk combined with the KLX master cylinder, but I imagine it would result in more of an increase in stopping power over the KLX disc+KDX master cylinder combo although a lot less controllable.

 

I wonder how the master cylinder would do with an aftermarket wave rotor.

 

so is it not worth it to just upgrade the rotor? it should be mentioned that overall braking control would also be greatly improved by matching the front springs to rider weight. I'm too damn fat for mine and under hard braking the front really nose dives

 

I can't say for sure. I know people that have tried only changing the master cylinder and the improvement is only marginal.
I would guess that changing the rotor will increase your stopping power, but you wouldn't have the outstanding control you have with the KX Master Cylinder.

Perhaps there is a pioneer in our ranks?

 

That's a geat combo. I already have a 320mm wave rotor and will be installing a KX master cylinder soon. I just need to get one of those 'banjo bolt brake light switches.' Still need to do some measurements to make sure I'm ordering the right size. Anyway, it's a tiny brake light switch that doubles as a banjo bolt. Just replace your master cylinder banjo bolt with that, hook up the existing wires and presto...a dual sport master cylinder rises from the dust!

 

I'm interested in the banjo bolt switch too since I lost the front brake light function by installing an ASV lever.

Unfortunately the parts breakdown doesn't specify the complete size:

92153 92153-0627 BOLT,OIL,L=23

This might be it?

http://cgi.ebay.com/ebaymotors/MOTOR...QQcmdZViewItem

 

Of the two size choices you found in that listing, I think the 10mmX1.25mm will fit. I'm going to do some more research before ordering, because I know of someone who has already done this. Hopefully I can post the info by the end of the day if domestic tranquility issues permit.

P/N: 12-0010
10mm dia x 1.25mm thread pitch.
20" wire length with terminals.
Fits most Japanese street and off-road motorcycles. Also fits most Nissin and Tokico brake master cylinders.

 

Moordan, I bought a banjo bolt switch today (30% off woohoo!). The size for the KLX250S (and KX250) master cylinder is in fact 10mm dia x 1.25mm thread pitch. I believe that wasP/N: 12-0010 on the page you were looking at.