Newbie brake question

So I finally got my cb750k working and took her for her real maiden voyage today. Bad part is, when I got down to the bottom of the hill into town, my bike didnt want to stop very well. I had to use my transmission for most of the slowing down.
So here is the newbie question, most of my previous bikes have been brand new and stopped really easily, are these old 70's bikes supposed to be very sluggish when trying to stop fully?
If not I plan to rebuild the brake caliper, master cylinder and add new pads. Any other tips to improve stopping?

First, you need to really clean the caliper pistons. There is a good chance that you don't need to rebuild the calipers and master cylinder. Follow the instructions here to clean the pistons:
http://www.lyndallracingbrakes.com/service_tech.htm

Additionally, I like to lube the outside of the pistons with silicone caliper lube. Don't use brake fluid, grease, or moly caliper lube for the outside of the pistons. Brake fluid is hydroscopic, and will attract moisture outside of the caliper seals. Petroleum products are incompatible with brake fluid.

Here is the stuff:
http://permatexelite.info/permatex-24110-ultra-disc-brake-caliper-lube-8-oz-brush-top-bottle

If the caliper pistons are rusted, you will have to replace them and rebuild the calipers, otherwise just start with a good cleaning and lubing to get the function back. Of course, you should also flush the whole system out with new brake fluid.

As for the pads, just deglaze them by laying a sheet of 80 grit paper on a flat surface, and renew the surface of the pads. I like to chamfer the leading edge of the pads, too. Part of my process for doing brake jobs is also to coat the backside of the pads with Disk Brake Quiet. This is optional, but it does help prevent me from having callbacks due to noisy brakes.

As for the rear brakes, (drums I assume,) pull them apart and inspect. A lot of times you will get a little bit of rust on the drum, and the particles of rust will grind up into a fine polishing powder similar to rouge. It will polish the brake shoes and make the rear brake really suck. Clean it out, and use 80 grit emery to roughen the shoes and clean the drum surface. Pull out the actuation cam, clean it, and lube it lightly with moly caliper lube. Put a tiny bit of it on the cam surface where the end of the shoes sit, too.

maddog5150 said:

So I finally got my cb750k working and took her for her real maiden voyage today. Bad part is, when I got down to the bottom of the hill into town, my bike didnt want to stop very well. I had to use my transmission for most of the slowing down.
So here is the newbie question, most of my previous bikes have been brand new and stopped really easily, are these old 70's bikes supposed to be very sluggish when trying to stop fully?
If not I plan to rebuild the brake caliper, master cylinder and add new pads. Any other tips to improve stopping?

Click to expand...

had the same problem on my 74 CB750 when I first got it. A temp fix for me was bleeding the system. But, it's probably a good idea to go through the whole system. There's no reason why yours shouldn't stop well.

The guys are right. First step is to get the most out of what you've got and fit braided lines while you are there. It will never stop like a modern bike though. Brakes have come a long way since the bad old days.

But a well set up old system should work well enough for most conditions. If you are used to modern brakes with very light pull, old bikes that require a heavy grab may not suit you. If you still ride a modern bike, it may be better to convert your old bike to modern components.

I tried jumping from a well set up drum brake bike to a modern bike one race weekend and that was "interesting".

Thanks for the tips guys. I dont have any modern bikes anymore but I'm glad I took it out at night and not during California rush hour lol. As far as fluid goes, if I'm flushing the system, would it be worth it to move up to DOT 5 fluid?

maddog5150 said:

would it be worth it to move up to DOT 5 fluid?

Click to expand...

No.

DOT 5 doesn't really have any advantages worth thinking about, and you would not want to try switching unless you disassemble the whole system, and preferably, rebuild all the components. You would not want any remnants of DOT 3/4 fluid in there. DOT 5 actually has some degree of compressibility, so it would detract from brake performance, not enhance it.

Agree with ADC.

Thanks. I knew that about DOT 5 but was going to rebuild the system. I ordered a new hard line, crush washers, steel braided hoses, and master cylinder rebuild kit (figured I might as well since I was odering parts), and pads. Hopefully I can get this bad boy to stop! The first ride I took her out, my cousin with a ducati wanted to go for a ride and lead me through some twisties, I'm glad I declined haha! The suspension is also fucked but thats for another thread...

Wait, you want your brakes to STOP???? thats just silly, my bike knows no such restrictions...blah blah blah

I did what alpha dog said and the calipers were CLEAN. I was really surprised as they came apart very easily. The piston aside from the cap was very smooth and free from rust and crystalized break fluid and the the o-ring looked almost new. I'm hoping the issue now is the master cylinder.
Right now I'm boiling the caliper and am going to clean up the inside nice even though it isnt bad. Probably slap some caliper paint on it as the guy before me butchered it trying to polish it. Also need to rough up the rotor.