Rebuilding the master cylinder is a piece of cake. CLEAN CLEAN CLEAN is all I can say. Remove the line, handle and cylinder. Disassemble, clean it out with a quality brake parts cleaner and compressed air if you can. Some brake parts cleaners will leave residue or water like substance behind so prior to reassembly you want to flush it out with new clean brake fluid and blow it out once again. The kit to rebuild it cost under $40.00 online.

I removed both calipers, lines and cylinder, rebuilt the master cylinder, with brake pads in the calipers placed a dummy plate in each caliper and bled the system off of the bike. Use a piece of pipe or whatever is handy for a handlebar blank. Then i hung the master cylinder in a position with the handle pointed up in the air and kept the calipers in their respective lower positions while bleeding and left it over night.. this allowed possibly trapped any tiny air bubbles from the rebuild to migrate away from the master cylinder piston.

 

The best mod i had so far is went for 2 to 2 brake lines at the front with dot 5 fluid; and of course clean and rebuild just makes it works like new again

 

Is it possible to use DOT 5 fluid in a system designed for DOT 4? I've always wondered what might happen. It's one of those things that's stated quite boldly, as if any deviation from the prescribed fluid might make the entire braking system dissolve into a mist before your very eyes.

What's the difference between DOT 4 & 5 anyway? I'd love some learned brake fluid guru to explain.

H

 

I'm no guru, but here goes. Dot 3 and 4 (which eat paint) are able to absorb a certain amount of water, and as they do this the fluid will change, the boiling point changes etc and stopping power can respectively change under extreme situations. Their ratings are related to heat handling characteristics and water absorbing qualities until you reach dot 5. Dot 5 is completely synthetic, the boiling point is higher, and absorbs no water it is more stable generally speaking. The take from dot 5 is that water which may enter the system (condensation slowly enters the master cylinder or calipers under certain circumstances) will collect normally in the bottom of the caliper or master cylinder and cause corrosion, thus prompting a strict schedule for flushing vs dot 4 being more forgiving in regards to moisture. It is extremely important when changing from dot 4 to dot 5 to get ALL traces of fluid out of the system. Completely disassembling and cleaning the master cylinder, calipers, and lines is suggested. A lot of people have probably done without, and don't even realize the traces of old fluid left are hampering their efforts to improve the brake system by upgrading the fluid. I hope that helps.

 

Oh it's dot 5.1 not dot5 that I used; dot 5 is silicone based and 5.1 is without silicone.
It just higher boiling point and I found it last longer than 4 or 3

 

stunter mods ftw


on ebay
F4i Honda Full Throttle Dual Quad Caliper Braket Stunt Handbrake w 80" Line | eBay



Magura Radial Master Cylinder 195 Stunt 16mm 636 F4i R6 | eBay