Author Topic: 350F brake sticking (Read 1893 times)

Neverdie38 · « **on:** June 12, 2013, 04:56:16 PM »

73' 350F front brake was slightly sticking to i broke it down, cleaned it, and lubed it. bled the caliper and now it sticks so bad i can't even move the wheel. any ideas?

BobbyR · « **Reply #1 on:** June 12, 2013, 05:28:12 PM »

Did you clean the small hole in the Master Cylinder. A strand of copper wire is usually all you need thin. That small hole is used to return fluid to the MC when you release the brake.

Neverdie38 · « **Reply #2 on:** June 12, 2013, 05:57:28 PM »

I did not. I pulled piston out as far as it would go without coming out, cleaned off any debris, lubed and reassembled. Did same for pad

jackseattle · « **Reply #3 on:** June 12, 2013, 06:41:44 PM »

I think you need to go back at it - remove the piston and inspect it. There is often rust and pitting on the piston sides, which causes the piston to stick or bind instead of sliding back down into the housing. Clean up the piston. If there is any pitting after you clean off the rust, get a new piston and piston seal. There are reproduction brake pistons that are better than the OEM part (thicker stainless layer) you can order from David Silver Spares.

If you can't pull the piston out with your hand, just keep pumping the brake until it pops out. But be ready to catch the escaping brake fluid, which can do a number on any painted surface it comes in contact with.

tomkimberly · « **Reply #4 on:** June 12, 2013, 06:52:06 PM »

Quote from: BobbyR on June 12, 2013, 05:28:12 PM

Did you clean the small hole in the Master Cylinder. A strand of copper wire is usually all you need thin. That small hole is used to return fluid to the MC when you release the brake.

+1

OP, you should rebuild the master cylinder too, after all, your life is at stake. Also if you haven't already done so, replace the brake hoses too.

Tom

Gordon · « **Reply #5 on:** June 12, 2013, 06:59:31 PM »

Quote from: Neverdie38 on June 12, 2013, 05:57:28 PM

I did not. I pulled piston out as far as it would go without coming out, cleaned off any debris, lubed and reassembled. Did same for pad

You didn't go far enough. One of the main culprits to a sticking brake aside from the already mentioned clogged fluid return hole is corrosion build-up behind the caliper piston seal, which you can't get to unless you completely remove the piston. Pull the seal out and gently scrape out the groove it sits in. Ideally you should replace the seal while you're in there, but I've gotten away with reusing old seals as long as they're in good shape.

Jasondo · « **Reply #6 on:** June 12, 2013, 07:32:38 PM »

I agree with the rest. Typically brake fluid should be purged completely and fresh stuff installed about every two riding seasons. Brake fluid degrades very quickly and crystallizes in the process. Pull the piston and replace the seal after scraping the all the dried up fluid. It's easy and seals are only a couple bucks.

BobbyR · « **Reply #7 on:** June 12, 2013, 07:49:47 PM »

You can use denatured alcohol to dissolve crystallized brake fluid. Dissolves it on contact.

flybox1 · « **Reply #8 on:** June 12, 2013, 08:19:45 PM »

Don't settle until that piston seal is replaced, and it's groove is spotless...

Shane72 · « **Reply #9 on:** June 12, 2013, 09:30:44 PM »

Yes, agree with fully removing the piston and giving the caliper the cleaning of it's life. You'll be surprised just how nasty it is in there.

Also agree with rebuilding the master cylinder. I've done two lately on early '70's SOHC's, and the leaf valve mechanism through which fluid is pumped and returned was nearly corroded solid. Hard to believe it wasn't frozen up completely.

The difference is dramatic and instantaneous.

All the best,

Shane

Neverdie38 · « **Reply #10 on:** June 13, 2013, 02:47:51 AM »

perfect. thanks for all the help. i figured i could get away without removing piston because it worked before but you're right, life is at stake. thanks again!!!

Neverdie38 · « **Reply #11 on:** June 13, 2013, 05:07:00 PM »

ok removed piston and it looked like mud in there. cleaned it all up and reassembled. still sticks slightly. piston was hard to get back in but i didn't lube it

BobbyR · « **Reply #12 on:** June 13, 2013, 05:49:45 PM »

Quote from: Neverdie38 on June 13, 2013, 05:07:00 PM

ok removed piston and it looked like mud in there. cleaned it all up and reassembled. still sticks slightly. piston was hard to get back in but i didn't lube it

One last thing. If you have the original rubber brake line, the rubber under the cords can collapse and restrict the return flow. If you do a search you will see it is fairly common.

Neverdie38 · « **Reply #13 on:** June 14, 2013, 02:36:26 AM »

ahhhhhhh didn't even think of that. know somebody with lines for sale? haha

tomkimberly · « **Reply #14 on:** June 14, 2013, 10:57:58 AM »

Purchase after market SS lines, oh, you can also drop the existing steel line to the caliper too.

Tom

flybox1 · « **Reply #15 on:** June 14, 2013, 11:17:01 AM »

SLINGSHOT CYCLES

Shaun is a forum member. good product used by many here.

tomkimberly · « **Reply #16 on:** June 14, 2013, 02:24:08 PM »

Quote from: flybox1 on June 14, 2013, 11:17:01 AM

SLINGSHOT CYCLES
Shaun is a forum member. good product used by many here.

Not to get into a flame war, but I've seen several posts that he's not the most punctual, some have complained of not hearing back from him for 2 weeks or more. Z1 on the other hand, has always provided good service to members of this forum.

Tom

Neverdie38 · « **Reply #17 on:** June 14, 2013, 05:42:40 PM »

price? link to website for lines?

Trevor from Warragul · « **Reply #18 on:** June 14, 2013, 06:52:35 PM »

http://www.wemoto.com/bikes/honda/cb_350_f/72-74/picture/hel_front_hydraulic_hose_-_standard_set-up/

I fitted these recently. Great quality at a great price. Ask for them to fit a male to male adapter (Goodrich part number GR306-03-32CH). I dealt with Pavel. Good customer service.

Also, prior to fitting these I had a slightly sticky brake (enough to make a continuous annoying squealy noise). I fitted a new piston & seal to the caliper, cleaned up the master cylinder, and it improved but the noise was still there. Once the brake lines went on the noise disappeared.

Trevor

tomkimberly · « **Reply #19 on:** June 14, 2013, 08:19:55 PM »

Read this thread, I posted the part numbers you need.

http://forums.sohc4.net/index.php?topic=49773.0

Tom

bryanj · « **Reply #20 on:** June 14, 2013, 08:27:51 PM »

When you removed the pisyon did you remove the seal and clean the groove out thoroughly? If not do it again. Caliper mounting should pivot freely on the pin and small hole in master should be cleaned. With all those OK the piston will not stick

Neverdie38 · « **Reply #21 on:** June 18, 2013, 05:20:31 PM »

ok i cleaned and made sure everything was good. i read how to adjust front brake with the lock nut and screw, my only question is do you do this before or after bleeding?

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Author Topic: 350F brake sticking (Read 1893 times)