KZ750-H1 Weak front brakes

Hello

I just bought me a 1980 KZ750-H1. I have a question about the front brakes. To me they seem weak. I can squeeze the handle as hard as I want and the brakes won't lock. They are twin disk, with the same caliper as the rear, but the rear works about 50% better. I changed the fluid (DOT 3, as per spec), made no differnce. I pulled the calipers and checked - both pistons move in and out. I have bled the system, but still don't have what I would consider a good front brake. The pads on it are Tokico C98FE, wearing even.
I have a good firm handle, so I don't think the master cylinder is bypassing. Am I overlooking something?

Thanks for any help.

Matt

This does not make much sense to me. On my bikes I can lock the front wheel if I squeeze hard enough. The dual discs on these bikes are more than enough to do that. However, let's think about this:

1. Is there any reason whay your brake line pressure is not being transmitted from the master cylinder? If you can get a decent squirt of fluid as you bleed the brakes, and you have a good firm handle when you apply the brakes normally, then this is not the problem.

2. Even though the brake system pressurizes properly, is something keeping your calipers from operating with full efficiency? I would consider disassembling the calipers to see if there is some corrosion or goop in the system keeping your piston from operating easily, and I would check to make sure the caliper slide pins are well lubed and moving freely.

3. If it's neither of the above, then it only leaves you pads and rotors. Are the rotors clean and free of any oil or other contanminants? (For wxample, when I had a leaky fork seal, the fork oil put a light coasting on one of my rotors. The decrease in braking was noticable.) You should clean the rotors and the pads thoroughly with brake cleaner, and if there is any chance the pads have been contaminated you should change them for a new set. (It may be possible to clean them, but it is likely any oil has saturated into the pores of the pad material, and will continue to lubricate the friction surface over time. Some people will clean them, then sand the surface down to all new material. sounds like to much work for a part that only costs $20 a set new.) While cleaning the rotors, make sure to get not only the surfaces (both sides), but also the insides of the rotor drill holes. Oil can hide out there, and ooze out when you get moving.

If this does not solve the problem, consider switching out your lines for a steel braided set. I have done that, and my handle is very VERY firm. It gives me great comfort as I zoom across the SF Bay Bridge in rush hour traffic.

Post edited by: apeman, at: 2006/05/21 20:33

Thanks for the quick repsonse. I spent a few hours today cleaning the caliper pins (one of the 4 was a little stiff - 3 were fine). I cleaned the discs well with brake cleaner before reassembling. I moved each piston out probably 3/16 to 1/4" and pushed it back in. I have a good squirt when bleeding.

I am to the point that I just ordered caliper rebuild kits and brake pads all around. I am looking for a master cylinder rebuild kit, but haven't found one yet (aftermarket).

The rotors are a little rough, but nothing major. I would assume rough would make the brakes work better to some degree.

Thanks again.

mjohnson2981 wrote:

I am to the point that I just ordered caliper rebuild kits and brake pads all around. I am looking for a master cylinder rebuild kit, but haven't found one yet (aftermarket).

Here ya go!


KZ750, KZ1000, KZ1000, KZ1300 FRONT MASTER CYL. KIT

MASTER CYLINDER KIT KZ550 KZ750 KZ1000 KZ1100 KZ1300 KZ

i just had kinda the same problum on my 650.after thinking my brakes still had a spongy feel it dawned on me to get a brake line pincher (snap-on,$10)and to elimanate one cailper at the splitter and bleed them one at a time.after i did them both, it was a world of difference. nice firm lever and locks right up. now the rear is a different story. had to get the master rebuilt to get the pedal i wanted. good luck!

Thanks for the links - I searched for about an hour and couldn't find them on eBay. Apparently I just wasn't looking in the right place.