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Author Topic: CB750 F2 1977 Master Cylinder Rebuild  (Read 990 times)

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Offline zalion0

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CB750 F2 1977 Master Cylinder Rebuild
« on: January 12, 2022, 02:46:21 AM »
Hi all, I was wondering if you could help me. The next stage of my project is to rebuild the stock master cylinder. I've cleaned and cleared out the existing one and the rebuild kit has arrived. Does anybody have an exact guide for type of master cylinder, all the ones I've seen so far are for a different (e.g brake fluid bowl is a plastic part vs all-in-one metal).

I've checked the shop and Clymer manual but these appear to be slightly different to what I have. My understand of the order is

Rubber Boot - Circlip - Washer - Piston (with secondary cap)- Spring - Check valve.

I've noticed on some other threads and videos, some kits are supplied with a pink ish grease. My kit was not. What is this grease and where is it applied?

Many thanks :)

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Offline Stev-o

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #1 on: January 12, 2022, 09:39:45 AM »
I sold my 750 F model a couple years ago but my MC did not look like yours, has it been modified?

Here's the fiche...

https://www.partzilla.com/catalog/honda/motorcycle/1977/cb750f-a-750-super-sport/front-master-cylinder
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Offline Don R

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #2 on: January 12, 2022, 09:53:34 AM »
 I'm not an expert but that looks like a gl1000 M/C. It could take the same kit, but I'd check it out first.
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Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #3 on: January 13, 2022, 12:38:18 AM »
It hasn't been modified and as far as I can tell is the stock master cylinder. I'll take some more photos shortly.
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Offline newday777

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #4 on: January 13, 2022, 02:48:16 AM »
Quote from: zalion0 on January 13, 2022, 12:38:18 AM
It hasn't been modified and as far as I can tell is the stock master cylinder. I'll take some more photos shortly.
Sorry but that master cylinder is not the stock master from your 1977 F2. (I included your picture)
The stock front master cylinder reservoir was cast as 1 piece on the master. See 2nd picture...
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline newday777

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #5 on: January 13, 2022, 02:57:51 AM »
Like Don said your master cylinder is more likely from a GL1000
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #6 on: January 14, 2022, 12:31:23 AM »
Thanks all, I was also looking at other photos as well. This is also a F2, same colour etc and year and appears to have the same master cylinder! The mystery continues haha!

Looks like that GL1000 Master Cylinder also takes the same rebuild kit I have here, so we maybe in luck.

Thanks for all your help so far everyone  :D

« Last Edit: January 14, 2022, 12:35:33 AM by zalion0 »
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Offline Doobie

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #7 on: January 14, 2022, 03:59:09 AM »
I rebuilt a CB900F MC the other day and I figured it out by looking at a parts diagram, which shows the order in which the parts go together.

I can't think where you would need grease when rebuilding an MC but I've bought brake caliper kits that included red rubber grease for the gaskets to make it easier to insert the piston into the barrel. You could use any grease really.
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Offline newday777

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #8 on: January 14, 2022, 07:54:15 AM »
No grease is needed. Just dip the rubber cup in a cap of fresh Dot4 to help it slide in...... It's worked for years doing that.
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #9 on: January 14, 2022, 07:58:11 AM »
Awesome, I’ll do that. Will attempt the rebuild this weekend!
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Offline BenelliSEI

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #10 on: January 16, 2022, 05:42:00 PM »
How’s your bike running? Get the tabs sync’d and sorted?
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Offline Don R

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #11 on: January 16, 2022, 05:46:14 PM »
 I wonder if this was a running parts change that sometimes occurred during a model run?
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No matter how many times you paint over a shadow, it's still there.
 CEO at the no kill motorcycle shop.
 You don't need a weatherman to know which way the wind blows.

Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #12 on: January 17, 2022, 01:02:52 AM »
Quote from: BenelliSEI on January 16, 2022, 05:42:00 PM
How’s your bike running? Get the tabs sync’d and sorted?

Slow progress, but getting there! The carbs still aren't idling properly (despite me cleaning, cleaning again, ultrasonic cleaning and re-confirming all passages and jets) so I do need to sync them I believe at some point. I'm also going to bite the bullet and replace the carb to engine rubbers as these are 40yrs old plus! Its a bit cold in the UK at the moment, so working in the shed without a heater is a bit of a mission! I'm doing as much extra as I can indoors (so brakes, dials etc) to make the most of it. Next big tasks I want to complete is getting the bike hoisted up, so I can remove front forks and replace seals, change the tyres, clean up the wheels etc. Then I'll be started on the back (so same again, wheels, brakes, forks etc) and finally clean out the inside of the tank.

Its a slow progress and every job seems to involve buying a new tool (snap ring pliers, grease gun etc) but loving it all so far!
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Offline Medyo Bastos

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #13 on: January 17, 2022, 06:10:22 AM »
Sure is 1 pretty bike!


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Offline bryanj

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #14 on: January 17, 2022, 07:03:32 AM »
Are you on the UK forum? SOHC.CO.UK
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Offline Translations

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #15 on: January 17, 2022, 01:25:05 PM »
Any idea of this would be a worthwhile upgrade for a F2? Sure would be nice to see the level of your brake fluid.
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Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #16 on: January 27, 2022, 05:24:45 AM »
Figured, i'd share some more progress! Master cylinder rebuild kit should be here tomorrow, the correct one this time! Ready to sort at the weekend. I've also used the grease gun method as well and have managed to extract the pistons from the callipers. Still need to clean up the grease and so on. This is their current state from sitting for 38ish years!

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Offline bryanj

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #17 on: January 27, 2022, 08:39:21 PM »
You need new pistons
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #18 on: January 27, 2022, 11:09:06 PM »
Agreed, they are badly pitted. I’ll be ordering seals as well.
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Offline bryanj

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #19 on: January 28, 2022, 03:51:04 AM »
Use a dental pick or similar to clean all the crud out of the seal grooves especialy the corners, a dremel dont wor it just polishes the crud
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #20 on: January 28, 2022, 04:25:08 AM »
Awesome thanks Bryant, I guess I can be quite firm with the dental pick and not worry about gauging the calliper?
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Offline bryanj

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #21 on: January 28, 2022, 04:28:55 AM »
You can feel the crusty crud in there, dont remove lumps of alloy though
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline zalion0

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #22 on: January 28, 2022, 04:31:06 AM »
Perfect, appreciate your help :)
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Offline newday777

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Re: CB750 F2 1977 Master Cylinder Rebuild
« Reply #23 on: January 28, 2022, 05:02:10 AM »
Quote from: zalion0 on January 28, 2022, 04:25:08 AM
Awesome thanks Bryant, I guess I can be quite firm with the dental pick and not worry about gauging the calliper?
Firm yes. Keep the dental pic in the seal groove.
But....Do not scratch the bore!
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A
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