I have a master cylinder which I got from a 2007 ZX-6R for free. It's so much better in terms of braking performance. However since the ZX uses an external fluid reservoir I can't get a good setup for that. I had a plastic reservoir just bolted to a metal plate, but the hose connection was off to the right so it would allow air into the system if I let it sit overnight with the bars turned to the left. Anyone know of any good options for external master cylinder reservoirs I should look into?

 

Use a different reservoir and use a small piece of aluminum stock to make your own mount. I always try to use the tiny 15cc (I think) reservoirs for Ducati clutch masters if I really think I need one. Otherwise I just use Tygon tubing and the breather cap from Honda.

 

I personally wouldn't ever want to just use a little tube with no reservoir.
Here's what I had that wasn't working. It was fine when upright, but air would get in if I left it on the side stand with the bars turned left for extended periods of time.

 

Air shouldn't be getting in regardless of bar and reservoir position, there is an actual mechanical problem with your setup.

 

I can't imagine any other way for air to get in. The whole system holds pressure just as it should. I think when on the sidestand with the bars turned the reservoir becomes lower than the master cylinder itself, so air can flow up into it if the fluid drops below the connection point at any time.
I painted it as an illustration of what I think is happening.

Anyway I'm going to try to find a reservoir where the connection is on the bottom instead of the side, and try to make sure I mount it high enough this can't happen. Anyone know of any to fulfill this need without spending much?

 

eBay...

There's dozens of options.

But, it shouldn't matter. The cup has a diaphragm on it that contracts and expands so there doesn't need to be any air in the cup. I have my hose currently mounted underneath my bars and clutch master on my bandit with the reservoir sitting *at best* level with the master - and I don't have any problems. All I did was fill it after I bled it while holding it up, put the cap on, then routed it.

It's also a Kawi Nissin master cylinder, and I understand what you mean about the inlet being awkward and there not being a mount on the master itself like most others...

 

That was an excellent illustration FYI lol.
I have been thinking about putting the 07+ RR radial master on my bike. Perhaps that resivoir is what your looking for?