I need some help fellas. so I only run one brake upfront. I don’t know if that has anything to do with it so I just wanna throw that out there. I bought a brand new Kawasaki OEM master cylinder rebuild kit. Everything came with it brand new not just the seals, the whole pistons and everything I tore the front brake caliper, completely apart, cleaned out all the ports all the holes wiped all the pistons off made sure they were smooth put everything back together.also I have core Moto lines. brand new DOT4 brake fluid. now the problem I’m having is my brake lever handle gets extremely hard to pull in and start breaking. All the return ports have been sprayed out everything’s new. What else could be the problem or is that just how it’s gonna be using one caliper. I use one caliper because it’s 1/8 mile track bike only. Trailered to and from only no street riding.

It's hard with two front brakes but in a good way. I think what you're experiencing is the natural consequences of having half the brakes. It's hard but it's only half of the braking power. I'd look into an aftermarket master cylinder but it's going to have to be one that is too aggressive for two front brakes. The caliper might even come into play but I think the MC is the first thing to address.

Hard yes. Takes up way less liquid to move so for a better feel, add the line can caliper back. That, or run a single motocross master for one disc, or deal with a harder lever pull.

What you have feels worse than OEM with two brakes up front. ...because you only have one. Hard lever, soft brake because there's only one brake. Hard lever you have to pull harder to make the single brake slow you down. Maybe you want a softer MC then. Personally, I'd live with it. If the bike is only used for racing, there should be no emergency braking. If there is, you had bigger problems. I'd prioritize going faster and as long as you can slow down and stop, that's the sacrifice you make for reducing weight. If you are unable to slow to safe speed, you need to address that

I might be reading this wrong? Is your lever pull hard before actual braking occurs or just hard and aggressive once applied? Do you run stock or shorty levers which would be harder due to reduced length leverage? Do you get good fluid flow with no lever resistance with the master or caliper bleeders open or is there still lever resistance? I've run both one and two front brake setups with the stock master cylinder and lever and have only found the single system to be a bit more aggressive but I wouldn't say it was hard in any way.

Thanks everybody for the input. I was thinking to myself maybe it’s just because you know one lever one brake line and a short distance. I do use Shorty levers and it’s not extremely hard. I have put the bike on a stand, rolled the front wheel master the brake let go of the brake and roll the front wheel and there is no drag or anything so I’m pretty sure the Pistons are going back in like they should. It’s probably just the price. I’m gonna have to pay using only one caliper. Thanks again