Topic: Poor front brakes

[colined2]

Merry Christmas to all members
I restored my 72/74 CB750 10 years ago and only ride it occasionally. In that time it has done approx. 10,000 miles.
In all that time the front brake has been terrible barely able to stop me quickly. At the time I had the front master cylinder totally cleaned, piston and seals replaced and bore checked for any damage. I made sure the 2 holes in the reservoir were free of any debris. The front caliper was thoroughly cleaned, piston checked and new seal fitted. I purchased from the motorcycle wreckers 2 secondhand brake hoses, I blew through them and they seemed OK so I took them home, cleaned them and fitted them to the bike. I bled the brakes and the handle felt good as if no air was present. I took it for a ride and I had to pull heavily on the lever to stop. The lever movement was good and didn't feel spongy but the braking was poor.
My questions are:
Do you think the brake hoses by being so old could be the problem?
or
Should I replace the master cylinder with a non genuine one?
Apart from that the bike is fantastic, all genuine apart from Hondaman points replacement setup.
Hope anyone has some suggestions.
Regards
Colin Edwards
All

[Deltarider]

Colined, there has been a thread on brakes not that long ago (September) Read from reply #3 on. http://forums.sohc4.net/index.php?action=search2
Maybe there is something in it for you. Begin at reply #3.

I realise the following is more an addition to that thread, than that it adresses your issue.
Apart from in the wet where our front brake really sucks, I don't think our brakes were that bad. Yes, you need more pressure than with more modern bikes, but I maintain stopping power was more than adequate and performance was well within the law.
There are two things that may lead to the subjective impression that our front brake was poor.
The forsaid difference in pressure ofcourse is one, but also later bikes had much longer (softer) suspension travels than ours which were quite spartan. Whenever I rode other bikes, I was always impressed by what I took for a better front brake, but I later realised that the deeper diving of the front suspension, can also give you the impression the brake is more effective. An example: a CB500 had a front suspension travel of just 121mm IIRC, the later CB650 already had 142mm!

[Don R]

 I've been on these bikes with very poor stopping and also some that seem to really brake well. Both with stock components. I've been sanding the stock pads on my belt sander to remove the glaze and sanding the rotor to get a better surface for them to work with. The brake hoses can also be an issue, I'd look at getting new ones, the rubber inside can bunch up under pressure causing resistance to flow.
 I'd also clean the caliper inside, dried brake fluid builds up under and behind the piston seal. It may cause the brake to drag causing it to glaze the pad or could make resistance to the piston moving.

[newday777]

Colin
You have 2 problems.
1. The old rubber hoses need to be replaced as the rubber has broken down and stretches as you pull the lever and thus you loose effective full pressure to the piston in the caliper. Trying to reuse old hoses to stay original on a rider is folly. It won't stop the bike. The rubber hoses are dead after 5 years of age.
Spend the money and get new Stainless Steel brake hoses. They come in black covered so it looks similar to the stock hoses but the major difference is the Stainless steel mesh under the cover that holds the pressure from expanding the hoses and you get full pressure where you need it, to the caliper piston so you get good stopping with the brakes again.
2. If you are like most, you probably didn't bleed the master cylinder at the banjo bolt after rebuilding the master cylinder before bleeding the caliper. Many think that you just have to bleed at the caliper but it doesn't get the air out at the master no matter how much fluid you pump through or suck through the system.
When a master cylinder is new or rebuilt and empty of fluid, you have to bench bleed it(old school brake knowledge), to clear out the air in the master. You can use the banjo bolt as a bleed nipple. First, have the gas tank off the bike to protect the paint. Then cover the frame and motor with plastic sheet of some sort to protect the paint from drips of brake fluid. (You can put an old bath towel over the plastic sheet if you want too). I put a rag under the master cylinder to further catch brake fluid.  Then pump the master cylinder as normal to bleed 5-6 times and hold the lever, crack open the banjo bolt to bleed it. Tighten the bolt and Repeat 2-3 times to insure that all the air is out, then bleed out the system at the caliper as normal.

[Deltarider]

[...] I've been sanding the stock pads on my belt sander to remove the glaze and sanding the rotor to get a better surface for them to work with. [...]

Newday, if one prefers to do it by hand, what grit sandpaper would you recommend for 1) the pads and 2) the rotor?

[newday777]

[...] I've been sanding the stock pads on my belt sander to remove the glaze and sanding the rotor to get a better surface for them to work with. [...]

Newday, if one prefers to do it by hand, what grit sandpaper would you recommend for 1) the pads and 2) the rotor?

That was Don.

[Deltarider]

Ooops! Sorry for that, the question was meant for Don. I've always thought you could not do much with our type ss disks, apart from cleaning.

[newday777]

Ooops! Sorry for that, the question was meant for Don. I've always thought you could not do much with our type ss disks, apart from cleaning.

John D(BenelliSEI) had a good post last week on what he does to the ss disc to resurface it.

[Deltarider]

I've read that post, but I'd like to have confirmation from others. The reason is that I was always told: you can't do much with our type of disks apart from cleaning them with brake cleaner.

[seanbarney41]

colined2, basically, every part of the cb750 braking system can use improvement through careful set up and parts selection.  Both of the changes you propose can result in much more powerful front braking.  In my experience, the stock master is the weakest part in the system.  Virtually anything more modern will be a big improvement.  I have often used sport bike/standard model masters from the 1990's purchased used from ebay with the same size piston (14mm).  I have found these to be a huge improvement in braking power that are available in shapes and sizes that can be easy to fit and unobtrusive appearance.

[MauiK3]

I also found I had a sticky caliper puck at one point. I took it apart, chamfered the edges and re-assembled it with a tiny bit of lube. I also put some anti squeal goop behind the puck. Not sure if that helped but mine don't squeal and they stop pretty well.
1973 K3 750 dual discs, stock master cylinder

[PeWe]

Cast iron disc will improve
https://www.ebay.com/itm/273994779212?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=LDyds-rfRVq&sssrc=4429486&ssuid=XgCEg0CPSya&var=&widget_ver=artemis&media=COPY

That seller has for CB750 and 500.
Complete rotor or disc only, drilled or not.
Terry has mentioned this in one of his threads. But he lives closer

Another thing how to keep it to not rust that much.

[bryanj]

Cast iron only improves the wet braking and from bitter experience i can say you dont want a perfect brake when its raining!

[HondaMan]

Lots of good ideas here, just tossing in my 2 penny's worth:
1. What brake pads do you have? If they are replacement units, that may be the most of the weak stopping if they are any brand of "environmentally friendly" pads (EBC's versions come to mind, specifically). I have seen these stop so poorly as to make me wonder "what broke?" after replacing just those pads. Pads with bits of sintered brass or copper in them are better than not having them: those bits both indicate better pads and tend to aid in preventing the disc from glazing over time.
2. If you don't mind its appearance, you can cut/file/saw a pair of grooves across the face of the disc, both sides, from the center to the outside edge, opposite each other like a big 'scratch' across the disc faces. While this won't help with the aforementioned 'bad pads' issue, it will help to shed water when wet and prevent squealing from glazed pads (we used to do 4 each side, but 2 each side seems to be enough). It's definitely NOT the OEM look, but then my trusty 750 is a long way from that phrase (beginning with the Vetter). Mine is mountain-road-worthy as it sits in the garage, which over time was a collection of changes and mods suitable for the non-straight, anti-level, foot-wide-road-cracked roads around here.

[PeWe]

My K6 has working brakes after it got an extra at front. (Dual front brakes)
This despite DSS cheap pads.

My K2 had also the DSS pads, replaced them with Vesrah "Green" pads. Not better.
Worked in lower range of legal speeds.
Replaced them with EBC semi sinter FA012V that improved a little.

My car got new brakes last year.
The Ferodo Eco Friction front pads felt like very harsh sanding stones direct out of the package.
 
I wonder how long the Brembo slotted rotors will last.
Really good stopping power. I try to not brake that hard to not grind down the rotors too quick.

If I could find same type of brake pads for my bikes, I should order.

[grcamna2]

I like Ferodo sintered pads/shoes when I can find them..

[MauiK3]

I didn't like the look of iron discs, too much appearance upkeep. My drilled rotors up front seem to work fine with a stock size MC and Honda pads

[BenelliSEI]

I've read that post, but I'd like to have confirmation from others. The reason is that I was always told: you can't do much with our type of disks apart from cleaning them with brake cleaner.

Use a grinder (lightly)  as I described. Makes a huge difference, with nos pads.

[Tom R]

And if you don’t have an extra hub and axle laying around…. Yes, that disc is zip tied on the wrong side and backwards. With a disc deglazer, a drill, and a friend to spin the wheel while you work the drill, you can get good results.
But as stated earlier…. New SS lines and a proper bleeding.
I switched to an 11mm master cylinder. That gives a bit more feel I’d say, but not a lot more stopping power. In my opinion a 12mm or 1/2” master would be better.

[Nightshift]

Or if you have a lathe ... polish the hub, install disc inside out & grind, flip disc and grind. Voila. Ready for lacing. I know these are Harley parts but pretend its a Honda

[BenelliSEI]

Or if you have a lathe ... polish the hub, install disc inside out & grind, flip disc and grind. Voila. Ready for lacing. I know these are Harley parts but pretend its a Honda

Perfect! My Myford Super7 is just a bit small!

[seanbarney41]

Or if you have a lathe ... polish the hub, install disc inside out & grind, flip disc and grind. Voila. Ready for lacing. I know these are Harley parts but pretend its a Honda

Perfect! My Myford Super7 is just a bit small!

not to mention Honda hub is gonna be a little tough on the fingers

[Don R]

 I've also laid them on a soft surface and sanded them with a DA sander. Same with clutch plates.

[grcamna2]

I send my rotors to truedisk.net 
He first true's/straightens the rotor,then machines it for 100% contact on both sides.
I like what he does to make my stock discs stop to their maximum and takes the least off of them to accomplish his task. 
I think he's still charging $55 per disc although he gives me 10% off as I'm a repeat customer.

[Nightshift]

Ya they probably put it on a surface grinder. Can make it very flat that way.