Front master cylinder

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oldbikerdude
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Front master cylinder

Post by oldbikerdude »

So was going to prime the front brakes with new fluid, but decided to do a rebuild on the front master cylinder beforehand.
Took the plastic cup off with difficulty, but finally got if off after twisting it and working a couple of screwdrivers under the cup.
Look at the gunk that was in the O-Ring groove. I did scrape it out with a dental pick. Now nice and clean.
The small hole in the master cylinder is also open. I'm guessing it's about .010" diameter.
Will put it all together tomorrow and prime the system.
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steve murdoch icoa #5322
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Re: Front master cylinder

Post by steve murdoch icoa #5322 »

Fairly safe bet that downstream could be in the same condition.
I would be reconditioning the calipers as well.

Surprising how many jobs where i have used those dental picks from Princess Auto.

daves79x
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Re: Front master cylinder

Post by daves79x »

Yes, you need to completely disassemble the front and rear brakes, clean everything, INCLUDING the lines and all banjo bolts and the splitter. Renew any rubber parts that need it, but for sure get new master cylinder kits form Honda. Also check very carefully for pitting in the master cylinder bores. Not good if you find it.

Dave

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NobleHops
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Re: Front master cylinder

Post by NobleHops »

Ya so we reconditioned several dozen old braking systems at RestoCycle and although we have professional tools and the benefit of having made every possible error as we learned :-), sometimes we'd get a super firm lever and great performance, and sometimes we'd get something 75% as good. Could still lock the brakes and be considered functioning well, but not as good as a new system. We took stuff back apart, sacrificed chickens, tried every trick we have, but it was what it was. On the other hand, my own twin-shock with two-piston calipers from a DOHC 900 has GREAT brakes for a CBX using Honda parts, I don't think I've used better.

Something just occurred to me, duh: When I was building that bike 13 years ago I got a massive beat-down trying to get the brakes bled, and finally gave up and sent my MC out to a place on the east coast called Apple Hydraulics and they re-sleeved it. They charged me something like $200 and kept me waiting 2 months and dinged and gouged the part, and so I can't recommend them overall, but in terms of *function* I'd have to conclude that was the critical component.

JR and many other guys have more or less given up on trying to get good performance out of these old parts, opting instead to use radial Nissin MCs from the aftermarket, or some or other more recent Kawasaki. And so I guess I'm saying, if you're getting beat-down trying to get a hard lever and good initial bite out of your brakes using the stock MC, I think you'd be best served considering one of these solutions.

N.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

Larry Zimmer
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Re: Front master cylinder

Post by Larry Zimmer »

Somewhat a 'side bar' to this: For cleaning the gunk from brake m/c and calipers, start by placing the parts in a pot of boiling water for 15 minutes +/-. After that, let things dry and start with a stiff bristle nylon brush. This process takes out much of the crud with hardly any work. Then, it's a minor clean-up with the picks and scrapers.
Thanks to Dave Ditner -- God rest. (For those who didn't know Dave, he was a brake system tech at Ford Truck engineering.)
Larry Zimmer
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Re: Front master cylinder

Post by Rick Pope »

Dave was the one who told me about using JB Weld to repair caliper pistons. It works.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.

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Re: Front master cylinder

Post by Larry Zimmer »

Can't beat 'practical' engineering. Comes from the university of hard knocks -- not MIT. And, works better very often.
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oldbikerdude
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Re: Front master cylinder

Post by oldbikerdude »

Thanks for all the tips guys.
Did rebuild the calipers, new seals, and new pistons. The bores were in good shape.
Also added speed bleeders to the caliper, added them to the 86 Goldwing a few years back and really makes bleeding brakes easy.
Both master cylinders have new kits installed, just waiting for the 2 O-rings for master cylinders.
Thanks Dave79 for the tip about cleaning the splitter, had you not mentioned this, would not have done it.
That's for later today, snow shovelling first.

oldbikerdude
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Re: Front master cylinder

Post by oldbikerdude »

Picked up my O-rings at Honda, cleaned up the splitter, all the lines as well, installed the front O-ring under the reservoir and filled the reservoir with Dot 4.
Probably took an hour or so, but got all the air (I think) out by pumping the front brake with the bleeder valve open on one side, closed that one and then opened the other side.
Also turned the wheel to the right when priming the right brake and to the left for the left brake.
I found continually tapping the caliper, the lines and the splitter, with a soft hammer got most of the air out. The brake lever was starting to get a hard feel. I also tied the brake lever about half way back to grip overnight to get out the last remnants of air. Will check the feel tomorrow.
Tomorrow will hook up a plastic hose over the speed bleeder valve, crack it 90 degrees, and make sure no air left in the caliper.
On to the rear caliper after final touch on the front.

oldbikerdude
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Re: Front master cylinder

Post by oldbikerdude »

Well guys, finished off the front brakes, bled the caliper, but was done quickly, thanks to the speed bleeders. Little to no air in there.
On to the rear master and tried priming the system, worked on it for over an hour and did see air bubbles coming up into the reservoir, so I know the small hole was open. Made sure of that when I put new master cylinder kit in.
But I could not get fluid into the caliper, I don't know why, I left the bleeder valve open so I wasn't pushing against air.
Getting frustrated, I took everything off the bike, the reservoir, master cylinder and caliper as a unit.
I took everything apart, made sure the lines were clean and not clogged, they weren't. Also checked the tiny hole to see if it became clogged. It was open.
I filled up the caliper with fluid with hose attached, then I filled up the master cylinder and sealed it off, attached the reservoir and filled it partially, then reinstalled everything back on the bike.
Then proceeded to pump the brake pedal and within 5 minutes the pedal became hard and the caliper pistons were moving out, put in a block of wood to prevent them coming out too far. Pushed the pistons back in and ready to go. Did a quick bleed of the caliper and some air came out.
Anyone else have issues with priming the rear brake.
For me the front brakes were way easier to prime compared to the rear.

daves79x
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Re: Front master cylinder

Post by daves79x »

I think you are the only person to think the front is easier than the rear. I use a Mity-Vac and it takes about 2 minutes to do the rear. The front takes a lot more fiddling. I suspect you were air locked somewhere - the Mity Vac overcomes that. One other thing that sometimes happens is that upon rebuild, the caliper piston gets pushed in too far, preventing any fluid from filling the caliper and coming out the bleeder.

Dave

hondaman160mph
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Re: Front master cylinder

Post by hondaman160mph »

I agree with Dave, I use a Mity-Vac to bleed both the front and rear brakes.
It's faster, cleaner and gives better results.
Invest in a Mity-Vac, it's money well spent.

oldbikerdude
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Re: Front master cylinder

Post by oldbikerdude »

Come to think of it, the rear pistons were pushed in a bit far into the caliper when I installed them. I wonder if that was partly my issue along with a air block. I did notice that some fluid was coming out of the bleeder.

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