Hi!

Recently, my rear brake stopped working, and I figured it was due to the master cylinder. I found this thread that said you can replace the rear master with a Chinese one with great success, and with many people saying it's a very good option.

But, there were no step-by-step guides with photos, so here I am making mine. If you know something I don't, or want to correct something I've written, feel absolutely welcome to do so.

Before anyone scolds me, yes, I did pressure wash my entire bike right after doing this mod.

Disclaimer: This was done on a 1994 K1100LT. Other models should work, but some details may be different.

First off, here's my rear cylinder. Apparently I'm a very 'lucky' person with a master cylinder that is non-servicable, which, in addition to no cheap genuine used parts, is the reason I'm doing this.





First thing I did was unscrew it from the brake line, and then remove the entire unit+reservoir from the bike.


Then I took the side panel (with the brake pedal) off the bike. Took that opportunity to disassemble the entire brake pedal pivot assembly and put some grease on it, because why not. I removed the bolt that pressed in the old master cylinder, and threaded the new Chineese master cylinder into it until the holes in the cylinder lined up with the threaded holes of the side cover. Then I screwed the master cylinder to the side cover.

At this point the brake pedal, when pushed, couldn't bottom out the cylinder because it was binding. With the cylinder screwed into the side panel, I unscrewed the threaded rod from the pedal until it started binding at the beginning of its travel, and then backed up two turns or so.

Removed the excess thread with a hacksaw


The next thing I did was try to fit it to the bike, and find a nice location for the new reservoir. There was actually a perfect place for it - an unused hole in a piece of metal that was behind the side cover.



Unbelievably perfect placement.

Then, I unscrewed the solid brake line from the ABS II unit, and placed an M12x1 to M10x1 adapter into it.



I then pulled out the old, metal brake line form the bike (which wasn't easy and took a fair bit of bending it) and put in a new line - an 80cm line with a right angle on one side and a slight bend on the other.



So, everything is assembled, now to put fluid into it... But how to do it, if the input to the cylinder is from the bottom?

What I did is to flip the entire thing upside down!


I pumped the brake until no bubbles emerged in the reservoir. That means that there's no (or very little) air between it and the cylinder.

After that, I put the side panel back on. First I put a hose on the ABS bleeder, and put a big 50ml syringe on the hose. Unscrewing the bleeder and pulling a vacuum meant that the entire length of the new hose had air sucked form it fast. Pumping the brake all the time so new fluid is put inside the new brake line.

After that, standard bleeding procedure. What I did was bleed the ABS until no air bubbles emerged, then I bled the caliper, I went back to the ABS unit and then back again to the caliper. It probably could be done smarter and with less waste brake fluid, but I wanted to ensure no air in the system.



And, that's it! Here are some additional photos:



I tested this setup out very briefly on a few hundred metres of asphalt, The brake works very nicely, feels sharp. On some light sand or gravel, I can more easily lock up the brakes and activate the ABS than with the original cylinder.

If you want more photos, feel free to ask! I'll get up tomorrow and take them. Also, I'll be test-driving the bike tomorrow afternoon, so I'll report on that as well.

Nice job!  Welcome to the Chicom master cylinder club.  Take the $260 you saved and use it for fuel to take a nice trip. 

Screw BMW and their stupidly priced master cylinders.

Welcome to the Chicom club. A couple of Brickers using the method you used without the articulation of the cut down bolt have experienced binding. See link http://www.motobrick.com/index.php/topic,9364.msg76252.html#msg76252
Regards Martin.

MartinW wrote:A couple of Brickers using the method you used without the articulation of the cut down bolt have experienced binding.

I've experienced binding as well, what I did was unscrew the master cylinder rod until it started binding at the beginning of its travel, then backed up a turn or two. That way I could bottom the master cylinder without issue.

Is there a better way to do it? My initial plan was to use a joint of some kind, but there's very little space between the new cylinder and the brake pedal.

See the link I posted there are two slightly alternate methods. With either method you can just counter sink the head of the bolt using a vice and a suitable size drill as per .75 (Gryph]. Once done you wont look back. I will shortly have to buy another one as I am out of stock people keep on pinching my spare.
Regards Martin.

Thanks for taking the time to document the process StefanMajonez.  For all of us that have made the change to this MC we must have a very sizable number of kms/miles now with this alternate part.  I know that I am pushing 20k kms since I made the change.  It hasn't done anything other than what it is supposed to do since it got installed.

Countersinking the end of the ChiCom shaft to accept the pin on the pedal has worked perfectly on two different bikes for about 20,000 miles now.  The spring centered pivot on the master cylinder does a very nice job of accommodating the arc the pedal swings through.

With the money saved by using this master cylinder, get stainless brake lines and new pads and you'll have the best rear brakes you can buy.  Absolutely amazing feel and stopping power.

My new Chinese m/c has arrived and my thanks to Stefan for this guide and great photos. I’m not rushing to make the swap so I have plenty of time to get the remaining parts in. Just spent over an hour reading the development history of this solution, which is a reminder of how much work the hard core put in so that us newbies can just swan up and go “oh yeah, you just use the universal Chinese master cylinder swap”. So thanks all from the young engineer onwards. 
S

I was on my home from work yesterday afternoon and on a whim I decided to make a sudden slow down and quick turn and go down a road less traveled.  My lovely non OEM M/C locked up the rear wheel and blessed me with a little chirp.    The previous OEM M/C had been long past its ability to do this.  15 bucks - hell yah!

Woodie wrote: The previous OEM M/C had been long past its ability to do this.  15 bucks - hell yah!

When my unbraked chair is fully loaded for a trip I need a rear brake that can make itself heard so yes: 15 bucks - hell yah!

Like you guys, BMW had totally erased from my memory banks the absolutely heavenly sensation of a working rear brake. 

Then the Young Engineer introduced me to the cheapy from the ChiComs.  Hell, Yeah!

That looks pretty good.  Nice job!

Another way to skin a Roo.

“Pride goes before a fall” section.

When I put everything back together I over did the pedal adjustment and the brakes were everything I hoped for. Except the over adjustment resulted in the m/c piston being unable to return fully. In turn this meant that the caliper pistons couldn’t retract properly.
In turn this meant that after a 10 mile ride I experienced a loss of forward movement then stall.
Rear brake was locked on and smoking like a damp bonfire. 

Caliper dismantled, plastic cover discarded, melted seals replaced, everything cleaned, greased and re assembled. Now I cannot get back pressure into the system which is the problem I had before - which is why I over compensated on the adjustment (without thinking it
 through) in the first place.

I’ve flushed all the boiled fluid, can get good pressure at the m/c outlet, and at the caliper end of the stainless steel line but can’t make it carry through to the caliper.

Both pistons move, both pistons retract when pushed, both pistons will lock on when pumped but there is a barely noticeable increase in resistance at the pedal and the pad grip isn’t exactly snapping turtle.

I have used both the hand pedal pump method and the vacuum assisted. Run through litre and a half of fluid and spent 6 hours without progress.

Any thoughts?

Do you have the reservoir cover screwed on tightly when checking the brake pressure? Sometimes the mind wanders.

Laitch wrote:Do you have the reservoir cover screwed on tightly when checking the brake pressure? Sometimes the mind wanders.

More of an aimless shuffle really. 
When I tested at the cylinder with my thumb over the banjo outlet I couldn’t resist the pressure, so am assuming that reservoir to banjo is aok. Likewise testing at the caliper end of the brake line, not as conclusive as the olive was leaky when the swivel was unscrewed, but nonetheless, certainly a good flow coming out between the olive and the line.
Writing that makes me wonder if the olive should be leaky when unscrewed, but all the joints stay dry when everything is buttoned back up.

I’ve moved this to a new thread ‘cannot bleed rear brake’ as it is not a ‘how to’ (yet ).

Hi, does any one have a link where i can buy one please?

Hi John, that takes me to a fuel pump. Maybe I should clear my cache.

Chewbacker wrote:Hi John, that takes me to a fuel pump. Maybe I should clear my cache.

Sorry, I was reading the thread about the fuel pump before switching to this one and posted the wrong link. I have updated the link to the master cylinder that I bought. I am sure that many other master cylinders on fleabay do the job just as well.

87 K100LT
I'm replacing the rear master cylinder with the Chinese one and appreciate all of the guidance for the set-up. I'd like to order a replacement braided brake line that will replace the original (mostly due to the Chinese MC having a different thread pitch than the original. 
Can someone specify what fittings they ordered to accomplish this with either both ends having banjo fittings, or as the old line  posted below. (this poster had trouble with this new line configuration).
thanks.

I took my master cylinder down to my local brake specialist shop and he made one up on the spot. A hydraulic specialist shop should also do them. See this link for more information, and they now come in black. http://www.motobrick.com/index.php/topic,9364.msg116179.html#msg116179
Regards Martin.

WARNING do not use the Chinese supplied reservoir to master cylinder supply line. They are not rated for brake fluid they will disintegrate after a time dumping fluid over your rear tyre. I showed the remains to my local brake guy and he said it looks like vacuum line.
Regards Martin.

Thanks Martin.

Going to have to do this myself.  I'm wondering if this might work with less machining, since it has a pivot built-in to take the sideload off.  I measured and seems the mounting holes would actually line up:

Chinese Master Cylinder w/Pivot

I wouldn't try that one in place of the ones others have used.  The clevis that allows the pivoting at the cylinder probably messes up the geometry of the rod that pushes the piston.

Side loads on the cylinders that have been used are handled by the pivoting rod that is spring centered.  

The recommended master cylinder probably has well over a hundred thousand miles on at least 20 bikes that we know of, with no reported problems.

https://www.ebay.com/itm/Rear-Foot-Brake-Master-Cylinder-Pump-For-Motorcycle-Go-Kart-ATV-Dirt-Pit-Bike/313165982411?_trkparms=ispr%3D1&hash=item48ea25aacb:g:6~gAAOSwCDxd~H93&amdata=enc%3AAQAFAAACgBaobrjLl8XobRIiIML1V4Imu%252Fn%252BzU5L90Z278x5ickkRjLZq23gAR%252BKma9gM2Z1hgfdIeGeC3ErKqIreVl5ad9GBK9d5NUleaq1spRgojljZAfReeTSGaHvYTzz6%252FBmyY%252FkoW5jaAz3Ncf4gmOGeNMag3BoBytgXD98ZIuWFG7zh%252By1KnHBIODhaVTm2lsBq1GLvSigtyIixVFYPB0m8l%252BYQvfon4e%252B%252FiP0JxH1fbKaBMScfJ5ZRPUaPk0LIsWkyiK2G7BmnyYFtFSEHsmm67y3LxeRnkh%252F7JU5TB1YcXcqPzOYkV89qAy%252Fedfg7UTXFHpb1rBI3BrzdlxhVg%252B5bc%252BXvd0WGkIajDlwQpHvjkbXTC7WLPvw6n11jxqAe84XjH0N%252FyIFrd1a%252B6erv04BDBZURYCJGic3oucW0o6G9dAiRV1w70DZtUVqIlJZuayKtj1woV8T0TsYiiYb7j%252FQpb8iwhmrn%252FBeyMkBAI8rSO14WVoL1a7GHxZ9gwqVbNsES2cy9rFMpTSgb%252FLeWvPiDgTYyBsaGUB4ignxGw%252BGsRpzoE0Fqx7XgiUVNYRf1VI%252FDG4Hw0KeAcDuozJo%252FY7sP4nLraM%252FSQ9a5LP4VQFLhh4Hw39dq50HXblvlkYe%252Fo6VP0UYPvqYqilXpXIZjVZclCMO3lpa%252FND5GkvxVnKfmttpUwocpNv1gns3zcrxhZJAV8dgCJaINFlS8nbDnmKd9vgY2rKJqhi1VrGDDwGqGLvjB1%252BMWXAFEo%252F9OI8u8l9yHLWB4LgbH0q%252Fc%252B8sTgACSaF6LtyENRls0AgosCcc5jhm7g0XKjO6mwjWtu6y2IOV2l%252F2RdbZ9FtNlCa8%252BBbtl9I%253D%7Ccksum%3A313165982411d81d0893a69648e9a7b3232b4bf91ace%7Campid%3APL_CLK%7Cclp%3A2334524

Point-Seven-five wrote:The recommended master cylinder probably has well over a hundred thousand miles on at least 20 bikes that we know of, with no reported problems.

The master cylinder Point-Seven-five bought and installed has a bore of ~12.8mm. The one he recommended in Post #28 above has a bore of 14mm. The cylinder ad Zaubertuba is considering doesn't even list the bore size.

The OEM rear master cylinder bore on a 2V Brick is 11mm; on a 4V Brick it's 12mm. If the bore size is greater than stock, braking might take more effort. Apparently, Point-Seven-five's oversize cylinder is working satisfactorily but that might not be the case for other oversized master cylinders.

The cold comfort here is that the seller discloses measurement accuracy might be ± 3mm, so efficient braking could still be a possible outcome. I'd rather it be a certainty.

I've installed six of the WuFlu Master Cylinders.  I know at least a couple of them were 13mm and not one of them has a hard time hauling the bike down, especially the K75RT when I'm in the mountains with a full touring load.  

Coupled with stainless braided lines, the feel is sensitive and stopping power is very good with lots of reserve.  Strong enough that the only time I have triggered the ABS on my RT was on the rear wheel during a panic stop in rush hour traffic in St Louis.

If anything, the larger bore reduces the amount of pedal stroke necessary to stop.

Well, I see the diameter on the most recent recommendation is "about 14mm," lol. 

In any case, enough has been written and my current cylinder is so hosed it's plenty worth the experiment.  Ordered.  Thanks for the info!

I'm looking at getting one of these master cylinders but unfortunately all the links published in this thread are expired.   I even searched by the keyword "WuFlu Master Cylinders" on both Amazon and Ebay and can't find a thing.  

What are the critical specifications for this master cylinder so that I can select a correct one from the current offerings? Centre to centre mounting hole spacing, actuator length, bore size, etc. is what I'm looking for.

Rob try https://www.aliexpress.com/item/4000300579098.html? fitting guide http://www.motobrick.com/index.php?topic=9364.msg76252#msg76252
Regards Martin.

This one looks a lot like what I've been using.  I search for "pit bike master cylinder".

https://www.ebay.com/itm/185096737230?hash=item2b18a011ce:g:QwMAAOSw1PdhYT8u&amdata=enc%3AAQAHAAAA8GlHNPTsQnITTP4UVzO%2F%2FvZT7Q%2FZAaH3MaU75lv5ePF9KVTKSFjPHgYRikei10ONwoNrF5jCLR%2FTjyS%2BK9GA4wchJCucfd0uD1VjPkApc8l49ULkd2ttvMfXCi%2FqWVnkcjqE867AB1cWqOp2MccuM0IjluU5rGKjTPZMTcbLtnUcbT6fziNKuT2c7sjwZWUG5JWTamwzJV6K8tv%2B%2B3wOtK58YF8zoTWhs6jEx%2FFM2kE%2Fo9NuTM96ckxafQQeWwV%2BAIFY9yxa5VGQ7Mq1NNlWxOStb6ktrW%2FSwnV42DjLBBXvQHV1WlieW%2FnCiOptIY3efw%3D%3D%7Ctkp%3ABFBMhtyjlcxg

Rob I have one for you if you like.  I bought two when I changed mine as they were so affordable.

I'd be tempted to buy the VRWeare cylinder just to support the sick background music. 

Point-Seven-five wrote:
Screw BMW and their stupidly priced master cylinders.

Harsh but true

Would trying an allen head bolt with a dimple drilled into it be a viable option? Looks like I am next in line for this Sino-upgrade and will try this. Also, if a dab of grease was put in the dimple and a piece of shrink tube but over the allen head, the shrinking tube would squeeze out the excess grease and give a water tight seal and lubricated contact point.

I wouldn't try to reinvent the wheel here.  The original pedal and fittings with the ChiCom master cylinder rod shortened with two jammed nuts is the winning combination.  Elegantly simple and reliable.  No grease required.

I may be a bit confused as the pics showing the modified contact point aren't enlargeable and I just reread the motobrick thread for a better understanding. Yes, seems the wheel shall remain round on this one.

robmack wrote:I'm looking at getting one of these master cylinders but unfortunately all the links published in this thread are expired.   I even searched by the keyword "WuFlu Master Cylinders" on both Amazon and Ebay and can't find a thing.  

What are the critical specifications for this master cylinder so that I can select a correct one from the current offerings?  Centre to centre mounting hole spacing, actuator length, bore size, etc. is what I'm looking for.

Try "ChiVi Rear Master" 

I recently ordered one of these to speriment with. Only $9.13 shipped and can be ordered in black so you don't have to paint it like the gold ones.

https://www.aliexpress.com/item/3256802459554750.html

In Search Of:

Is there an online source or USA based store chain for this size adapter:


M10 x 1.0 female to M10 x 1.25 male


I will will be tapping out my Chicom rear brake master cyl. to use the original BMW rear brake line. 2 hours searching online was unsuccessful. Seems Internet search engine aren't what they used to be. :-(

Bricklayer wrote:In Search Of:

Is there an online source or USA based store chain for this size adapter:


M10 x 1.0 female to M10 x 1.25 male


I will will be tapping out my Chicom rear brake master cyl. to use the original BMW rear brake line. 2 hours searching online was unsuccessful. Seems Internet search engine aren't what they used to be. :-(

I spent some time searching for one of those too. No joy.

I think a banjo bolt will be the way to go.

Even trying trying to find a brake shop online to make a line is frustrating. I hate being stuck in Cleveland, Ohio, it is easier to find parts in Cambodia.

My ChiVi master cylinder is in US Customs now so I expect it by the end of the week. I'm going to try it on a non-ABS bike.

I plan to use banjo bolts at both ends. Once I have it on hand and can figure the best length I plan to order a ChiCom universal SS line.

Like this: 
https://www.aliexpress.com/item/3256801606082641.html

Upon further study I think it's best to get a universal line that has a right angle banjo at the caliper end.

Like this:
https://www.aliexpress.com/item/3256803019674938.html

"Upon further study I think it's best to get a universal line that has a right angle banjo at the caliper end.
Like this: https://www.aliexpress.com/item/3256803019674938.html "


Since I have a '85 non-ABS the I need a female on one end to connector to the steel line pipe coming off the caliper. I am assuming it's M10 x 1 threads. This is all getting to be no fun at all. 

Bricklayer wrote:"Upon further study I think it's best to get a universal line that has a right angle banjo at the caliper end.
Like this: https://www.aliexpress.com/item/3256803019674938.html "


Since I have a '85 non-ABS the I need a female on one end to connector to the steel line pipe coming off the caliper. I am assuming it's M10 x 1 threads. This is all getting to be no fun at all. 

You can ditch the steel line and just have a single brake line from the master to the caliper.  That's what BMW did in 1992.

The steel line was not used after 12/91. Instead the rubber line is 95mm longer. My non-ABS 91 K75S has the metal pipe. My non-ABS 92 K75S has the longer rubber line with no metal pipe.

It shows in the parts catalog:
https://www.realoem.com/bmw/enUS/showparts?id=0572-USA---K569-BMW-K%2075%20S%20(0563,0572)&diagId=34_0620

duck. wrote:
You can ditch the steel line and just have a single brake line from the master to the caliper.  That's what BMW did in 1992.

The steel line was not used after 12/91. Instead the rubber line is 95mm longer. My non-ABS 91 K75S has the metal pipe. My non-ABS 92 K75S has the longer rubber line with no metal pipe.

It shows in the parts catalog:
https://www.realoem.com/bmw/enUS/showparts?id=0572-USA---K569-BMW-K%2075%20S%20(0563,0572)&diagId=34_0620

+1 Duck. I made a braided line for the whole length and deleted the oem pipe. Must have at least 8k miles on it without issue.

Although a banjo bolt would work in the caliper, I did more poking around and finally ordered these parts so that I can have a line that goes straight into the caliper with a banjo bolt at the master.

The SS line has female threaded ends and comes with three banjo fittings. I'll probably use the 90 degree fitting at the master end:



At the caliper end I'll use one of these adapters so that the line goes straight into the caliper similar to the OEM setup: