Topic: Honda CB750 Brake Lines/Hoses - more discovery?

[kyle750]

We are working on the CB750 brake lines today.  Caliper came off easy but the bleeder valve looks seized and the metal pipe is heavily corroded. Sliding back the rubber boot it looks like the master cylinder was originally painted black but has faded to a matte grey.  I quite like the look of the faded to grey look.

The brake line splitter has what looks like a sensor on the other side?  I'm not sure what this is?

[kyle750]

I think I can just buy this repro caliper front side with bleeder valve and pipe.  The other 1/2 (back side) of the caliper is perfectly OK.

[Rookster]

The master cylinder was originally anodized black.  They fade to purple then gray in the sun.  You can remove the a anodizing with easy-off oven cleaner and a scrub brush.  The pressure sensor is the front brake switch.  You can certainly buy a new caliper relatively cheaply but with some heat you should be able to remove the bleeder screw.  If you decide to rebuild the old caliper use a genuine Honda piston seal.  I would recommend using braided lines instead of the stock rubber lines and pipes. 

Scott

[kyle750]

The master cylinder was originally anodized black.  They fade to purple then gray in the sun.  You can remove the a anodizing with easy-off oven cleaner and a scrub brush.  The pressure sensor is the front brake switch.  You can certainly buy a new caliper relatively cheaply but with some heat you should be able to remove the bleeder screw.  If you decide to rebuild the old caliper use a genuine Honda piston seal.  I would recommend using braided lines instead of the stock rubber lines and pipes. 

Scott

Thank You. Not planning on reusing the old lines (too old to be reliable).   I am looking to replace with new stainless braided lines (maybe black painted)?

Is there a set of braided lines For Sale on Ebay from a US Seller that you would recommend?

[kyle750]

You can certainly buy a new caliper relatively cheaply but with some heat you should be able to remove the bleeder screw. 

We will try to remove the bleeder screw with the skills of a recommended bike repair/machine shop.  I can't move it.

[kyle750]

Surprise, Surprise.  My german friend took one look at the bleeder screw, knocked it a few times with a hammer, channel lock pliers, and with super human germanic strength,  he got the seized bleeder screw right out. Danke Schön

Brake caliper piston is locked up.  We are now trying to unlock the piston by reinstalling the bleeder screw, caliper, and brake lines, fill with brake fluid, and use the pressure to try to unlock the piston

[seanbarney41]

yup, that's how ya do it...if the master cylinder doesn't work, try pushing the piston inward slightly with a hammer or a c-clamp, that will break it loose and you can pump it out.  If all that does not work, hook up a grease gun and pump it out with grease.

[HondaMan]

In REAL stuck cases I have used a grease gun, fitted to the pipe and steel line, to pump the caliper out. Messy to clean up, but works without much grunting.

[kyle750]

Many thanks Gentlemen.  I tried using  a C-Clamp to push the piston in but it would not move.  No luck with using using the master cylinder. Piston is still stuck.  Moving forward to using the grease gun method at a local bike/machine shop.

[Don R]

 Get a handful of paper towels ready, the grease gun is a lot safer than air which usually doesn't work but when it does it can shoot the piston across the room. You can buy a small grease gun pretty cheap, when you get the seal, also get a new bleeder.

[Jerry Rxman Griffin aka MuthaF'er]

Once the grease gun pushes out the piston (threads don't match if you try it that way but just don't force them together enough to strip threads), do yourself a favor and replace the stock bleeder with a Speed Bleeder. Grease gun is THE best way.

[M 750K6]

The master cylinder was originally anodized black.  They fade to purple then gray in the sun.  You can remove the a anodizing with easy-off oven cleaner and a scrub brush.  The pressure sensor is the front brake switch.  You can certainly buy a new caliper relatively cheaply but with some heat you should be able to remove the bleeder screw.  If you decide to rebuild the old caliper use a genuine Honda piston seal.  I would recommend using braided lines instead of the stock rubber lines and pipes. 

Scott

Thank You. Not planning on reusing the old lines (too old to be reliable).   I am looking to replace with new stainless braided lines (maybe black painted)?

Is there a set of braided lines For Sale on Ebay from a US Seller that you would recommend?

HEL have good quality braided lines, in black. The kit comes in the correct lengths, with replacement fittings and washers. Went straight on my 750.

[kyle750]

Thanks for the recomendation.  Would this work and look OK in Solid Black?

https://www.ebay.com/itm/405122273805

[rotortiller]

Before you buy brake lines decide on the handlebars and master cylinder. Right now all you have is junk, until it is verified useful. If you are interested in brake performance over OEM looks go for a suitable 1/2" bore master cylinder.  At this stage you could decide on something different from stock and require an altered brake line length. Those new lines in the picture have little give for twist when routing. I have found that custom brake lines work best when manufactured or accessed on the bike for both length and fitting twist. Applies to clutch cables often enough too.

[kyle750]

Right now all you have is junk, until it is verified useful.

Junk is absolutely correct.  Seized parts and old lines.  Nothing has been verifed as useful. I really just wanted to get the brakes working so I can take a short first ride safely.  1st ride is a long way off. In the meantime at least I can start the bike and hear the engine run. With no knowledge or experience and lacking solid skills I knew this would take a long time.  Nothing worthwhile is ever easy! Right?

[bryanj]

If the master require rebuild its cheaper and easier to buy the repo from Dave Silvers. I have not yet had the grease gun fail  to remove a caliper piston, just remember the threads are different so the pipe only screws in a couple of turns.
If you are replacing everything cut the steel pipe just above the nut and used a six sided socket to remove after warming the caliper body till its uncomfortable to hold, grease gun in pipe hole bleed screw nipped down and lots of paper towel and brake cleaner afterwards.
Dont forget to clean all the hard crap out of the seal groove with something like a dental pick.

[M 750K6]

.... Those new lines in the picture have little give for twist when routing. I have found that custom brake lines work best when manufactured or accessed on the bike for both length and fitting twist. Applies to clutch cables often enough too.

I found the HEL lines fitted perfectly fine. Good quality fittings too. Everything mated up very nicely.

I also went for HEL when replacing the brake lines on my 650 Bandit. A more complicated run of lines, connecting the two front callipers. Same experience. Fit straight out the box and good quality fittings.

[MauiK3]

Be sure to aim the caliper away from you, in case it takes a flying trip.

[kyle750]

Be sure to aim the caliper away from you, in case it takes a flying trip.

I hope to launch this piston to the moon

[Stev-o]

Be sure to aim the caliper away from you, in case it takes a flying trip.

I hope to launch this piston to the moon

Then use the air compressor trick!  Much more fun than the messy grease gun method.

[willbird]

Be sure to aim the caliper away from you, in case it takes a flying trip.

I hope to launch this piston to the moon

Then use the air compressor trick!  Much more fun than the messy grease gun method.

My dad showed me that trick with the caliper off a 72 chevy station wagon, he put a 2x4 in where the pads go so when the piston came out with a BANG it had a softer landing. Years later a co worker working at home stuck his HAND in that space before firing the piston out. I tried compressed air on one I was messing with it and it would not budge...grease gun walked it right out easily. NAPA had a fitting that would screw into the caliper and provide an adapter path to the 1/8 NPT on the grease gun hose.

[Bodi]

If you use a m/c with a brakelight switch, you can delete the junction. They tend to trap air bubbles that give a soft feel and reduced effective lever throw. There are also banjo bolts with switches.

[HondaMan]

Be sure to aim the caliper away from you, in case it takes a flying trip.

I hope to launch this piston to the moon

Then use the air compressor trick!  Much more fun than the messy grease gun method.

+1!

[kyle750]

A sunny new day and I am rethinking my strategy.  At the start my focus was on getting the bike so I could ride it safely (fixing the front brakes and forks).  I still think this is the right strategy but I now believe I have taken the wrong path.  I will not be able to fix the bike.   At a certain age you know who you are and should have a very good understanding of your strengths and also respect your limitations.   I greatly appreciate the advice and tips but I am not a mechanic and the bike would be better in the hands of a skilled mechanic who knows what they are doing. 

I'm sitting here leisurely sipping a nice cup of slow drip coffee and watching the birds hop around between palm trees and the jasmin bushes and I've come to the conclusion that finding the right person to work on the bike is the best direction going forward. I am not the right person for the job.

[PeWe]

Learning by doing....
It was a little bit scary when I pulled the engine first time and opened it.
Friends encouraged me and a manual with blurry photos from Haynes. Learned later it had  a mix of explanations from different years. Honda Shop manual much better.

Hondaman's (Mark Paris) manual a good read explaining more how to do, modifications included.
Get those manuals and enyoy the read relaxing in the shadow a sunny day.
Heineken can help. Thai beers give me headache.

Replacing parts is not that difficult. Be aware of not overtighten the small  bolts like M6 on covers. 5-7.5Nm
Long threads like 15mm can withstand 10Nm. Engine cases and clutch.

I have used a torque wrench 2.5-25Nm for the M6 since 2014. I had too many bad threads I had to repair and had repaired before.

Download the CB750 Shop manual. It is a good read. I have a new paper copy too for living room reading wirh clean hands.