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I used this DOT 5.1 fluid as a good replacement on other bikes. 5 is not good. Synthetic and mineral don't mix. Does this one work for our bikes?

I use exclusively DOT 5 in all my old bikes, but you're right, 5 and other types of brake fluid do not (and should not ever be) mix(ed). I go to great lengths to completely drain, disassemble, and clean all components before switching to 5.

Let the brake fluid flame wars begin!

Yes, that's it Buco. DOT4 can be mixed with DOT5.1, but not with #5. It would create jelly. My other bike has #4 recommendation and it was discussed on a related forum to safely use #5.1. In my case, ALL system will be spanking clean so either would work. But I am using the 5.1 for other bikes, so I will stick to it. I also changed lines to Teflon stainless steel braided lines on the Vmax. The old rubber lines expand and I am sure this would be the case of our KZt's. Since replacing them with braided lines the brakes became noticeably more responsive. I'd definitely suggest this upgrade to any of the old bikes.

I put braided lines on mine and the improvement was huge. Going to do the Busa over the winter as well.

Yeah, I've done that one another bike, much younger and modern by all standards by comparison, and the braided lines made a nice difference. For now I have other priorities with this bike, will leave this for upgrades when I see the bike on the road first.

One of the issues with DOT5 is that it easily aerates (holds air bubbles), which is very hard to get out of the system.

One thing I do with ALL my brake systems when "bleeding" them, I reverse bleed. I fill from the caliper, UPWARDS, so all the bubbles rise and exit into the master fluid pool. Then, I let the system sit for a while, and then compress the piston(s) into the calipers, pushing fluid upwards, and air out of the system. After that, I gently pump the system to put the fluid back n the caliper(s), and do it again. Usually, that gets the system to top notch level performance.

Dot's 3 and 4 are alcohol based, DOT5 is silicone based, don't know what 5.1 is.