Author Topic: Front brake lever has no play (Read 3962 times)

Johnny340 · « **on:** February 24, 2020, 09:45:41 PM »

I have a new aftermarket master cylinder, a rebuilt caliper, steel braided line, and new brake pads. I have apparently bled this thing well because the lever is rock solid. The only problem is that the lever/pads don't have very much play at all and the lever is at the very end of the travel range.
Here are a couple pics of the master cylinder (I don't remember the brand) and the caliper. I'll try to post a video link of the action (or lack there of).
https://photos.app.goo.gl/i9gpJA8ScQ3REiKA8

robvangulik · « **Reply #1 on:** February 25, 2020, 01:20:05 AM »

That caliper sits way too high over the disc....

Zunspec · « **Reply #2 on:** February 25, 2020, 01:53:15 AM »

Hello Johnny,

If your brake lever becomes firm almost at the first touch it could be you have a m/cyl suited for twin caliper/disc rather than a single caliper/disc. On a twin disc set-up the m/cyl needs to move more fluid and will have a piston in the 14 - 17mm dia range. A single disc set-up the m/cyl will have a piston in the 11 - 13mm range. With the larger m/cyl piston the caliper pistons mover further for any amount of lever movement and consequently the lever does not move very much. The small m/cyl piston moves less fluid and thus the lever movers further to apply piston pressure. Looking at your video the movement of the lever looks fine to me, but then I like a set-up where the lever pressure builds quickly. I have come across a twin disc m/cyl on a single disc bike and the lever felt like you were squeezing glass, about 2mm movement at the lever

.

Cheers Geoff

pjlogue · « **Reply #3 on:** February 25, 2020, 04:05:32 AM »

Quote from: robvangulik on February 25, 2020, 01:20:05 AM

That caliper sits way too high over the disc....

I agree. Looks like you are only catching half your puck with the rotor. Check to be sure the parts (caliper, bracket and fork lowers are what they should be.

-P.

Scott S · « **Reply #4 on:** February 25, 2020, 05:00:04 AM »

Possibly a 550 rotor and 750 caliper?
Did you center the caliper over the rotor? This won't fix the problem of the caliper sitting too high/possible wrong rotor, but it is possible to lock up the front wheel with the adjustment screw on the caliper arm.

Erny · « **Reply #5 on:** February 25, 2020, 05:06:34 AM »

Quote from: Scott S on February 25, 2020, 05:00:04 AM

Possibly a 550 rotor and 750 caliper?
Did you center the caliper over the rotor?

just wanted to write the same

BenelliSEI · « **Reply #6 on:** February 25, 2020, 05:24:48 AM »

That after market master cylinder has an ADJUSTMENT screw. I can see the tab? From the underside, brake loose the jam nut, and screw the stud in or out. I’t cut on an angle to allow taking up slack. You need to back it off. Take it off and look at the shape. It will become obvious what to do.

You have a cb550 disc on that front wheel. I have made the same mistake!

PeWe · « **Reply #7 on:** February 25, 2020, 09:05:45 AM »

Look like mine MC, DSS. Work really fine.
Why a play?
I have DSS MC on both my bikes. With single brake and dual. No play att all and not hard direct either. The hydrualic works direct, brake after pressing the lever some.

If hard direct tke caliper/ bracket must sit wrong. Adj screw with spring if you have , adjusted correctly?

I made a mistake on my CB750 with dual brakes when mounted the front wheel after s tire change.
I mounted the right caliper bracket and fender bracket in wrong order making the right brake caliper to sit not centered over rotor. Bone hard and wheel not free.

.

Johnny340 · « **Reply #8 on:** February 25, 2020, 10:48:59 AM »

You guys are amazing...Thank you!
Yes, now I see that the rotor is too small. It measures 275mm and has G04 stamped on it. Probably from a 550.
The master cylinder piston looks pretty large from the outside and is probably for the dual disc setup. It has to go. I see that adjustment screw which sets up the resting positing but the lever pull is not enough to modulate the (weak) brake action. Hopefully the power improves once I get the correct rotor on there.

BenelliSEI · « **Reply #9 on:** February 25, 2020, 11:43:42 AM »

I’ve got the same master on one of my bikes, with a single disc. It works great. Yours should too. Is it really bled and free of air?

Johnny340 · « **Reply #10 on:** February 25, 2020, 06:10:09 PM »

Quote from: BenelliSEI on February 25, 2020, 11:43:42 AM

I’ve got the same master on one of my bikes, with a single disc. It works great. Yours should too. Is it really bled and free of air?

It's so free of air that the lever only moves a small amount and you don't get any leverage when you pull it in. In that case, maybe I'll keep this master cylinder and see if the proper rotor helps with the feel and power. To me it just seems to not have enough free play before the pads contact the rotor. I'll make sure the brackets are proper when I have it apart. The adjustment screw is correct and if I try to make more gap on the inside pad, the outside pad just pulls it in and the adjuster screw sticks out on the inside??

scottly · « **Reply #11 on:** February 25, 2020, 08:49:36 PM »

The correct rotor is 295mm, and the stock master is 14mm. Are there any markings on the MC? Most newer ones have a circle with a line, which is the symbol for diameter, which may be a number for mm, or a fraction for inches.
At least for now, don't bother with the adjuster screw and spring.
The upper caliper mount goes directly against the fork lower, with the fender brace on top of the caliper mount.

Johnny340 · « **Reply #12 on:** February 25, 2020, 09:18:02 PM »

Quote from: scottly on February 25, 2020, 08:49:36 PM

The correct rotor is 295mm, and the stock master is 14mm. Are there any markings on the MC? Most newer ones have a circle with a line, which is the symbol for diameter, which may be a number for mm, or a fraction for inches.
At least for now, don't bother with the adjuster screw and spring.
The upper caliper mount goes directly against the fork lower, with the fender brace on top of the caliper mount.

Well, there's another problem with my setup which probably explains the poor centering of the pads and the lack of free play. I have the fender against the fork leg and the caliper mount inside of that! That would position the caliper with too much pressure on the piston. Thank you!
So other than the rotor being 20mm too small, wrong caliper mounting, and maybe the wrong master cylinder, it's perfect!

I don't see any markings on the master cylinder but here is an external pic of the plunger area.

scottly · « **Reply #13 on:** February 25, 2020, 09:33:54 PM »

Look at the other end of the master, where the nub on the hand lever presses on the end of the piston assembly.

Johnny340 · « **Reply #14 on:** February 26, 2020, 04:38:58 PM »

Quote from: scottly on February 25, 2020, 09:33:54 PM

Look at the other end of the master, where the nub on the hand lever presses on the end of the piston assembly.

It is small actually.

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Johnny340 · « **Reply #15 on:** February 26, 2020, 04:44:05 PM »

So I changed the caliper mount the way it should be with the fender towards the inside (caliper directly touching fork leg). Surprisingly the pads were not more centered afterwards with the caliper more towards the outside.

Sorry first pic is from before. See below

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jaytee-nz · « **Reply #16 on:** February 26, 2020, 04:53:11 PM »

It's hard to tell from your pics, but it looks like you may have fitted a CB500 caliper and arm, as well as the 500 / 550 disc.
That could explain the bad fitting and alignment issues.

Johnny340 · « **Reply #17 on:** February 26, 2020, 04:55:35 PM »

I definitely have the wrong rotor but that could also be the case. That's the wrong picture there from before. Here is the new mounting position.

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jaytee-nz · « **Reply #18 on:** February 26, 2020, 05:38:13 PM »

That angle of the arm definitely looks wrong.

jaytee-nz · « **Reply #19 on:** February 26, 2020, 05:47:57 PM »

This may help (or not !).
http://forums.sohc4.net/index.php/topic,101345.msg1652158.html#msg1652158

scottly · « **Reply #20 on:** February 26, 2020, 09:26:29 PM »

It is not a 550 caliper. It's an F0-F1 K7-K8 42.8mm piston caliper.
Johnny, it looks like there is a spacer washer under the head of the caliper pivot pin??

Johnny340 · « **Reply #21 on:** February 26, 2020, 10:07:27 PM »

Quote from: scottly on February 26, 2020, 09:26:29 PM

It is not a 550 caliper. It's an F0-F1 K7-K8 42.8mm piston caliper.
Johnny, it looks like there is a spacer washer under the head of the caliper pivot pin??

The first pic a couple posts ago was how I had it mounted before and the next post of mine (and here below) shows the new mounting position. I can't see the spacer you are referring to in the current setup. I did have one on the lower mount before to make up for the fender mount thickness. It's gone now and the black part is the disc guard bracket wrapping around. Let me know what you think in the pic below and how the angle of the caliper bracket looks. Can you confirm that it is for a 750?
Yes, remember having issues with the caliper rebuilt kit for this and ordered the 'wrong' one at first. It's all starting to make sense. I have a 750 rotor on the way now too.

scottly · « **Reply #22 on:** February 26, 2020, 10:23:51 PM »

OK, I can see the head of the pin more clearly in the last pic. Your caliper is a 750 caliper; the caliper mounts on the fork lowers are the same on both the 750 and 550 relative to the distance from the axle, and a 550 caliper won't bolt to a 750 arm because the bolts are closer together on the 550.

Johnny340 · « **Reply #23 on:** February 26, 2020, 10:41:21 PM »

OK so I must have a 750 arm & caliper and soon I will have the 750 rotor. I think that master cylinder might be ok after all. The good bleed and the steel lines make the lever pull like a rock! I'll post the final result once the proper rotor is on there.
Thanks again everyone for your input! You guys rock!!

BenelliSEI · « **Reply #24 on:** February 27, 2020, 04:05:43 PM »

Johnny...... in one of your earlier posts, there is a photo looking straight at the disc and caliper. The fixed pad and the disc are almost filling the entire gap in the caliper. Are you sure that pad is the correct one and really seated in the caliper??

Johnny340 · « **Reply #25 on:** February 27, 2020, 06:11:45 PM »

Quote from: BenelliSEI on February 27, 2020, 04:05:43 PM

Are you sure that pad is the correct one and really seated in the caliper??

I thought they were seated correctly but I'll double check when I am changing the rotor.

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Johnny340 · « **Reply #26 on:** March 05, 2020, 09:44:22 PM »

So the proper rotor is installed now and the pads looked good on the calliper, which is now mounted correctly. The play at the lever is still minimal and if I try to adjust the inside pad further away to create some play, the outside pad just pulls it over and leaves the adjuster bolt sticking out on the inside. Pics below show this as well as the distance the lever moves.

scottly · « **Reply #27 on:** March 05, 2020, 09:54:01 PM »

That must be a larger than stock MC..

Johnny340 · « **Reply #28 on:** March 05, 2020, 09:58:11 PM »

Quote from: scottly on March 05, 2020, 09:54:01 PM

That must be a larger than stock MC..

I found the bill for the mc.
It’s from vintagecb750 Part #: 08-0253 and is 5/8”.
Is this ok? The braided lines make for a rock hard pull...just not enough travel.

scottly · « **Reply #29 on:** March 05, 2020, 10:09:44 PM »

5/8'' (15.87mm) is way too big for a single caliper, IMHO.

Scott S · « **Reply #30 on:** March 06, 2020, 03:22:55 AM »

It should be the 14mm version.

PeWe · « **Reply #31 on:** March 06, 2020, 07:40:16 AM »

Davidsilver version is 14mm
https://www.davidsilverspares.co.uk/CB750K2-FOUR-1972/part_123912/

Johnny340 · « **Reply #32 on:** March 06, 2020, 09:50:10 AM »

Thank you all! I now know what I need to make it ideal.

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robvangulik · « **Reply #33 on:** March 06, 2020, 11:13:12 AM »

Quote from: Johnny340 on March 06, 2020, 09:50:10 AM

Thank you all! I now know what I need to make it ideal.

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Right, a half inch master cylinder

Johnny340 · « **Reply #34 on:** March 06, 2020, 12:14:06 PM »

Quote from: robvangulik on March 06, 2020, 11:13:12 AM

Quote from: Johnny340 on March 06, 2020, 09:50:10 AM
Thank you all! I now know what I need to make it ideal.

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Right, a half inch master cylinder

My Johnson is already a full half inch.

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scottly · « **Reply #35 on:** March 06, 2020, 09:39:51 PM »

Quote from: robvangulik on March 06, 2020, 11:13:12 AM

Quote from: Johnny340 on March 06, 2020, 09:50:10 AM
Thank you all! I now know what I need to make it ideal.

Sent from my SM-A705W using Tapatalk
Right, a half inch master cylinder

1+ A 1/2" MC should work well with your 42.8mm caliper.

Johnny340 · « **Reply #36 on:** October 12, 2020, 05:58:56 PM »

Just to close this off, you guys were correct (as usual). I installed a 14mm master cylinder in place of this 5/8" one and the difference is huge! Great modulation now with this smaller master cylinder on my single disc front brake.
Thanks again!

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Author Topic: Front brake lever has no play (Read 3962 times)