Topic: Light feel from front brake. Normal?

[Yoshimitsuu]

Hey all,

Just wanted some opinions on my front brake. I’ve heard that they really aren’t the best on the 750s but I’ve made a few upgrades and still feel that it’s lacking. So far I have:

- Replaced stock master cylinder with a Nissin Radial Master Cylinder (14mm)
- Installed stainless steel brake lines
- Installed EBC Brake Pads (front)
- Installed phenolic brake piston


What I have done:

- Bled lines multiple times
- Adjusted caliper to spec
- Running DOT3 brake fluid
 
The only thing that I have not done is changed the rotors. With that said, I rebuilt the brakes before testing the old brakes and I’m just feeling like the brakes are super soft. I have bled the lines the traditional way and with the Mightyvac and I’m coming up with the same results. On the Nissin, it allows for adjustment on the lever and Lu less I have it on the setting furthest away from the grip it can (with a bit of effort) bottom out the level. I know it’s not going to stop like a CBR but this isn’t normal, right?

Included is a video of me explaining this. I didn’t trust my explanation in the video so it’s much of what I stated above. Please help!

[evinrude7]

is the piston/pad completely retracting into the caliper when you let go of the lever?

[jaytee-nz]

Looks like you still have air in the brake line.
Where is your caliper mounted - in the normal place in front of the fork slider or behind ?
If it is behind, the caliper will be on an angle and will not bleed properly as the air cannot get to the bleed valve due to the angle.

[Yoshimitsuu]

Thanks for the replies guys. I checked the caliper and the piston doesn’t really move around much. If it’s supposed to retract completely into that cup, it doesn’t do that. If anything it sticks out a bit and when the brakes are depressed it’s not moving and if it does it’s maybe mere mms. I think I have my fender mounted right and I believe my caliper is mounted correctly. It’s next after the fork and then the fender mounts to the caliper end.

[Patrick]

Can you get more pressure by pumping the brake lever? If not, take the top off the brake reservoir. Pull in the lever and let it release. If you have most of the air in the lines out, you should get a strong brake fluid return. Don't just let the lever go. If you have good pressure if will shoot brake fluid almost like a water gun. Ease it out and see how much the fluid moves. It should be obvious.

If you do that and the air seems to be gone, you just might have a mismatch between your master and your brake system. The wrong size master will not work properly even with a properly pressurized system.

Patrick

[Bodi]

The piston should retract just a hair on brake release, so the brake doesn't drag/squeal. This is hard or impossible to see, but if you don't have a dragging brake after use (you should feel some friction spinning the wheel but it should turn without much effort)
Set the fixed pad to have a bit of clearance off the disk. There is a spec but not sure- 1/4 turn of the screw?
Do you have the OEM brakeline tee with pressure switch? Those love to trap air bubbles.
To clear out all the air, I pump the caliper piston way out (caliper split), avoiding popping it out of course. Then kinda roll it around to get any bubbles to collect the line connector, and press the caliper piston back in with a c-clamp (slowly, or brake fluid will spray way out of an open reservoir if you use the stock m/c). Repeat that a couple times then I move on to the tee and do the same procedure with it, turning and tapping it to get any bubbles by the line to the m/c. This is a pain but it has made a major difference in brake lever feel. With steel lines the brake feel should be very hard once the caliper has closed on the disk.
And no, you will never get CBR braking. You should be able to get the front tire howling a bit, but stoppies are not likely. There were once aftermarket cast iron rotors available that increased stopping power a LOT but rusted and looked like ass after no time at all.

[Yoshimitsuu]

Can you get more pressure by pumping the brake lever? If not, take the top off the brake reservoir. Pull in the lever and let it release. If you have most of the air in the lines out, you should get a strong brake fluid return. Don't just let the lever go. If you have good pressure if will shoot brake fluid almost like a water gun. Ease it out and see how much the fluid moves. It should be obvious.

If you do that and the air seems to be gone, you just might have a mismatch between your master and your brake system. The wrong size master will not work properly even with a properly pressurized system.

Patrick

I have opened up the MC and inspected it. When I pull in the lever and release, I am not getting the shot of brake fluid that you describe. It actually doesn't look like very much movement of fluid at all. This means that there is still air in there and I have to get it out.

The piston should retract just a hair on brake release, so the brake doesn't drag/squeal. This is hard or impossible to see, but if you don't have a dragging brake after use (you should feel some friction spinning the wheel but it should turn without much effort)
Set the fixed pad to have a bit of clearance off the disk. There is a spec but not sure- 1/4 turn of the screw?
Do you have the OEM brakeline tee with pressure switch? Those love to trap air bubbles.
To clear out all the air, I pump the caliper piston way out (caliper split), avoiding popping it out of course. Then kinda roll it around to get any bubbles to collect the line connector, and press the caliper piston back in with a c-clamp (slowly, or brake fluid will spray way out of an open reservoir if you use the stock m/c). Repeat that a couple times then I move on to the tee and do the same procedure with it, turning and tapping it to get any bubbles by the line to the m/c. This is a pain but it has made a major difference in brake lever feel. With steel lines the brake feel should be very hard once the caliper has closed on the disk.
And no, you will never get CBR braking. You should be able to get the front tire howling a bit, but stoppies are not likely. There were once aftermarket cast iron rotors available that increased stopping power a LOT but rusted and looked like ass after no time at all.

Alright, so it not being obvious that it is moving might not necessarily be completely wrong. I am going to inspect it and I'm going to go back and revise the stationary pad clearance to ensure that that is to spec. I do have the OEM brakeline tee with pressure switch still. Should I just crack it to get the bubbles out and seal it? My Nissin master cylinder has a plug for a brake switch but it's not bullet connectors so I wasn't really sure how to adapt it to my bike. If I don't have to use the OEM pressure sensor I wouldn't.

[Patrick]

Along with my CB750s, I have other bikes, which most have hydraulic clutches to go along with hydraulic brakes, so I've bled a lot of lines. It's easy, if you are a little patient.

First, double check all connections for leaks. A tiny fluid seep is a massive air leak. Then, open up your master cylinder. Pull in the lever and release it slowly. If you are getting a poor fluid return, you should see tiny bubbles. If you do, leave the bleeder closed and just work the lever and look for bubbles. As the bubbles disappear the lever pressure will grow. If you are not getting tiny bubbles on the return, you may not be getting correct pressure from your master.

Don't worry about working the bleeder until you start feeling pressure on the lever. It will be obvious. Might have to pump it 70 times, but slowly.

Patrick

[Yoshimitsuu]

Along with my CB750s, I have other bikes, which most have hydraulic clutches to go along with hydraulic brakes, so I've bled a lot of lines. It's easy, if you are a little patient.

First, double check all connections for leaks. A tiny fluid seep is a massive air leak. Then, open up your master cylinder. Pull in the lever and release it slowly. If you are getting a poor fluid return, you should see tiny bubbles. If you do, leave the bleeder closed and just work the lever and look for bubbles. As the bubbles disappear the lever pressure will grow. If you are not getting tiny bubbles on the return, you may not be getting correct pressure from your master.

Don't worry about working the bleeder until you start feeling pressure on the lever. It will be obvious. Might have to pump it 70 times, but slowly.

Patrick

I just ordered new crush washers and intend on going through the system. When I moved my handlebars I went from stock to superbike bars and had to move the lines a bit. While the brakes were soft beforehand, I'm sure cracking open that banjo bolt did not help my situation. When I pull the lever and release it I see no bubbles. It's as if no fluid is moving and it definitely doesn't shoot up. This has me worrying about the MC now. I understood that the stock MC was 14mm so I replaced it with a 14mm Nissin Radial MC. Could I possibly have made a mistake and maybe I needed a different size?

[Patrick]

Is this a new master? It sounds like you have a plugged fluid return hole. If that's the case, you will never get pressure.

Try this, disconnect the brake line at the master. Put your thumb or finger over the fluid hole and pump the lever. Are you getting any pressure?

Patrick

[Yoshimitsuu]

I replaced the MC last year when I overhauled the bike. I didn't ride the bike much as I finished everything to make the bike road safe late October into early November. I topped off the fluid and then didn't ride the bike during the winter only to set it up for this summer. I will try disconnecting the line at the MC tomorrow. I heard using a thin piece (such as the high E from a guitar) to dislodge a plugged fluid return hole. Is there a better option?

[Patrick]

If the master is pumping correctly, a wire can clear the splooge hole.

[disco]

Have you tried the “lever pulled in overnight” trick? Tie the lever back to the bar & leave overnight. I read about it here on the forum. Worked for me. All air eventually makes its way up & out.

[Don R]

 What disco said, I saw a photo of the Yoshimura shop and they had a brake setup on a bench with the lever tied back. It works for me  too, it compresses the bubbles, makes them smaller and they lose their grip on the inside of the lines and float to the top. On the next pump they will vent into the M/C.

[evanphi]

Yep same. That's what I do every time I bleed my brakes. I also use a speed-bleeder.

[Patrick]

I've never had to tie back a lever, but I will not argue against its efficacy. If you follow my method you are slowly pressurizing the lines from the top. The pressure of the mc pump forces out the air. I rarely need to bleed hydraulic lines when I am done.

Patrick

[Yoshimitsuu]

I think what I’m going to do is assemble the parts that I need and am just going to go through the system over the weekend. I searched through old threads and found that people were generally split between how effective the swap to a Nissin MC is. Some said it improved braking by a huge margin while some said it made little to no difference. Here’s hoping the former is true! I’ll also ensure that hydraulic brake switch is torqued up right and that no air is passing through. Thanks for all the help guys!

[Yoshimitsuu]

Update: Over the weekend I went through the entire brake system. This is what I did:

- I installed a new front caliper and inspected the seal
- I made sure the banjos are crushed and that there are no leaks
- I made sure lines run straight with minimal turns
- I checked the clearance of the stationary pad (set to spec)
- I flushed old brake fluid and installed new fluid
- I installed a speed bleeder and bled the brakes

At this point, my lever is pretty firm but I’m not feeling it bite. I still have to keep it in the furthest setting on the Nissin MC to get the most out of it and even with that if I gorilla grip it I can probably get it all the way to the grip. The line is pressured but it just feels a bit weak for my taste  and I’m not sure if that’s just the nature of the SOHC beast or what. I haven’t owned another motorcycle so I can’t really say

[Yoshimitsuu]

I also currently have the lever tied overnight.

[jaytee-nz]

The calipers on these bikes are primitive compared to newer machines so they will never feel fantastic. At best they will provide adequate braking with reasonable force from your right hand.

[Bankerdanny]

He has a radial with a remote reservoir, not the OEM with the built in. I am not sure that the fluid return works the same. When I was bleeding the radial I installed for my rear disk there was no noticeable fluid return.

[754]

 I  often find this helpful.
Take a ten mm wrench, start tapping line at the bottom then slowly work up to top. Don't hurt to do it 2wice.
 Often helps a lot.

[scottly]

Update: Over the weekend I went through the entire brake system. This is what I did:


At this point, my lever is pretty firm but I’m not feeling it bite. I still have to keep it in the furthest setting on the Nissin MC to get the most out of it and even with that if I gorilla grip it I can probably get it all the way to the grip.

Is this when actually riding the bike and using the brake, or just when squeezing the level standing still?

[Yoshimitsuu]

Update: Over the weekend I went through the entire brake system. This is what I did:


At this point, my lever is pretty firm but I’m not feeling it bite. I still have to keep it in the furthest setting on the Nissin MC to get the most out of it and even with that if I gorilla grip it I can probably get it all the way to the grip.

Is this when actually riding the bike and using the brake, or just when squeezing the level standing still?

I just finished going over the brake system yesterday and was not able to take it for a ride. Tomorrow I will do that. I think I was expecting better brake results so I was hesitant. My observations are from having the bike stationary.

[754]

You can scare yourself and have the tire chirping with stock master cyl, dual rotors and braided lines..
 Maybe I scare easy, but it stopped pretty good.