I have a super pocket bike with hydraulic brakes, and the rear brakes don‘t work. I was pretty sure it was the brake fluid, so I bled the system a few times over, and still, the caliper moves very little (an eighth of an inch, maybe). There are no leakes in the the system. What could be wrong?
We had a heck of a time bleeding the clutch on an S-10 We tried gravity bleeding and everything. We just had to keep pumping the heck out of it. We did this for a couple days and then we got in and just tried them one day and they worked. We was thinking about renting a vacuum pump. Maybe try using a vacuum pump. You can probably rent them for free at an auto parts store with a deposit down.
I don't know what a pocket bike is but I have had similar brake problems. I had a Chevy truck that the left front brake that wouldn't work then after going down a long hill it wouldn't release for a long time and got hot. What it was is there was a metal strap that held the hose that goes to the caliper and the strap got rusty between the strap and the hose and as the rust grew it started pinching the hose and the hose got so small that the fluid couldn't get to the caliper when the brakes were applied and on the hill the brakes were on a lot and the fluid finally got thru then could get back out fast enough so the brake stayed on and got hot. If your bike has a metal strap some where that may be causing the problem or if it is a steel line all the way to the caliper it my be mashed almost shut. Take the brake line off at the caliper and push the brake and see if a lot of fluid squirts out. If it doesn't the problem is in the line or master cylinder.
-The master cylinder (The cylinder with actuator lever) may be faulty and allowing pressure to flow past the seals. You will have no leaks, as the pressurized brake fluid will pass back into the reservoir. Overhaul seal kits are available. -You may be improperly bleeding the brakes, not removing OR allowing more air into the brake system. -Possible that the slave cylinder (The one that is actuating the brakes) is locking up. The piston sometimes corrodes, or the housing itself can warp, causing them to lock togetherpermitting little or no movement. Overhaul kits are available, but better idea to replace the assembly, as the problem may return. Try this With a full master cylinder, pump the brake lever 2-3 times to allow pressure build up. (More pumping only invites any air/brake fluid mix to start foaming). While holding the lever down (like you are still braking), release the bleed valve (on slave cylinder). A little shot of brake fluid/air will escape the cylinder. Close the port off completely.repeat as many times as needed until pressure builds up. At no point should you release the brake lever while the bleed port is open. That will allow air to be sucked back in. If this doesn't work, it is a mechanical or seal problem which requires disassembly. Here in Japan, these bikes are quite commonplace. Slightly larger versions (50cc) are street legal. Good luck!
