Rear Caliper Reservoir

Just finished a few add-ons to my 02 WR426 and noticed my rear brake caliper resivor is broken at the bolt hole and it is just flapping there. Wanted to know if any of Thumper Specialists :applause: have ever heard of or seen an aluminum or anodized rear resivor for the 02 WR426. I have looked all over the internet and still nothing. I would not like to use OEM, because living in the desert the weather is to extreme for the plastic mount and i know it will break again. Any help would be appreciated

Thano you all in advance.

I went to ace hardware and bought a 6-inch by 1-inch strip of stainless steel so it wont rust. Bent it around the resevoir and redrilled a hole and used a little jb weld and it works fine. But they are only $13 from thumpertalk oem. hope this helps

Another option for you. Keep an eye out for someone parting out newer WR or YZ that has the intgral reservoir/master cylinder. I bought a complete rear brake assembly that included the caliper, brake hose and pedal too for $70 and it bolted right on my 99 WR.

scott h. Does increase braking power or anything of that sort. I might just go that option. Because i am getting ready to throw a couple hundred dollars into my bike.

Ok cool TY all for the replies. scott_h what year did yamaha start making caliper and resivoir as one, and will it just bolt on or do i need to do some modification to the bike or unit?

Again ty all for help.

Ok cool TY all for the replies. scott_h what year did yamaha start making caliper and resivoir as one, and will it just bolt on or do i need to do some modification to the bike or unit?

Again ty all for help.

I believe it was 03.

bygdd is correct. There's no difference between the P/N (5UN-2583V-00-00) for the 2003 through 2006 YZF/WRF 250-450.

I've notice no noticable change (good or bad) in braking performance as far as I can tell after about 7 desert races and enduros running this setup. Good luck.

Thank you for the replies. I will start looking for a newer rear master from an 03 on up. That does seem to be the ticket, exspecially since it will just bolt right on.

Again thank you and safe riding

I've got a 99 and 02 yzf and figured the reason the plastic resivors don't last is that they are too close to the exh. pipe and don't have a heat shield. I got a small sheet of stainless steel and made heat shields for both of them, works great and the cash out is nearly 0.

Scott, i am going to look for a master cylinder from an 03-06, i think i found one from an 03 YZ and before i purchase it, i just want to verify. This is master cylider only no hoses or pedal, will it bolt right on to my 02 WR and the linkage and existing hose bolt right on? I looked up both models and the spec book shows pics of both and i can't notice a difference. Please if you know, advise me with this situation. Thank you very much.


I'm pretty certain the 02 brake pedal and hose will bolt up to the 03 master cylinder even though the part numbers are different. It looks like the change in the caliper design had more influence on the hose bend on the caliper end than the master cylinder end.

You can do part number comparisons for different year bikes here:

One more thought. I ground off the mounting tab on the subframe for the old brake reservoir, but I don't recall if this was required to allow for clearance for the newer one piece master cylinder or not. I have since upgraded my subframe to an aluminum unit off a later model YZ, so I can't tell for sure any more.

Here's a couple of pics for you:


99 WR with 03 master cylinder and 04 YZF subframe


99 WR stock master cyinder config (with added brake light switch)

Hope this helps.

Scott, Thank you very much for all the info, and for those wonderful pics. I will pick up the master from the 03 like planned, it looks as though it should work. Again thank you bro.:applause:

The plastic tab on the resevior on my '98 WR is cracked, but not broken. There was a small aluminum guard on mine that I replaced with a set of frame guards. I wrapped a small tie strap around the resevoir and the guard, no more problem. :applause:

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