Front brake pump rebuild.

Kivi · 06-13-2019, 03:55 AM

Hi,
My front brake pump - master cylinder was leaking oil. I disassembled it, cleaned, took measurements and put back, ordered rebuild set from AliExpress. 30 days later I received the rebuild set. Than I again disassembled my old master cylinder, set side by side with the new set, took a photo. They were close to identical in all measures. So I installed the new kit, bleed the brake with new oil.... It was functioning very good. I used DOT4 fluid.

But, after a week or two of use, I noticed that my brake lever started to have some trouble RETURNING after braking - returning of the lever was slow. Also, I noticed that the lever would, sometimes, go all the way to the end, while providing little braking power!

So, I dont like these situations, esp. with brakes! However cheap the china bike was, the brakes should never be "cheap". So, I disassembled the brake pump, removed the piston, again set side by side with the old piston, took a photo.
Here I post the 2 photos. First photo is when I received the package, second photo is from today.

Kivi · 06-13-2019, 04:09 AM

I am shocked what happened to the piston rubber seals! The seals on the new kit from AliExpress enlarged and deformed! This is why the return of the lever was so slow, and this is why the lever was sinking to the end without enough brake power.

But, what happened to these seals?! I used dot4 fluid, I have rebuild brake pump enough times to know how to do it. Repair kit may be of bad quality. The original (old) kit lasted 15 years with no problem or rebuild! The new one lasted 10 days?!

2LZ · 06-13-2019, 10:12 AM

That's ridiculous. Thought about buying an entire new assembly? They're cheap.

https://www.amazon.com/HIFROM-Replac...ateway&sr=8-15

OneLeggedRider · 06-13-2019, 11:08 AM

Look at the poor casting of the piston, I'm surprised that it even worked for a week and obviously the seals weren't meant to stand up to brake fluid. Even on a jap bike rebuilding the master usually doesn't work because the cylinder itself is worn. Just buy a new one, brakes are too important to skimp on.

Megadan · 06-13-2019, 03:17 PM

I have rebuilt several OEM Honda Master Cylinders with great success, The bore is critical though, and if it has any damage it is usually best to get another one.

As far as those seals, they were trash to begin with.

Kivi · 06-13-2019, 05:40 PM

I like to keep original equipment on this bike, up to a certain point. Some of the parts on this bike, I'm sure, are of very good quality, comparable to Japanese. Not all, through. One example is when I fall once on the right side, hit the rear view mirror hard. Bent the steel chromed mirror holder while aluminum brake and mirror holder (thread m10) survived. Not the best example but you got the point.
I can get cheap Chinese complete brake pump from here for 15$, but, how are the quality of their rubber seals? Is it the quality like these rubber seals from AliE.?!
Also, this brake pump assembly has a nicely positioned thread for the rear mirror, few cm in front of handlebar.
So, I would like to keep the original brake assembly. I dont like to replace whole parts that served me well in the past with parts of unknown quality. I will always try to rebuild. Im not sure if the bore is ok. The new seals from Ali haven't leaked at all if that is relevant. I will try to examine the bore, maybe take a photo, but it would be hard to capture.

But, I wanted to point users about the quality of SOME goods from AliExpress. You wait upto 40 days for the order to arrive, you spend some effort to replace the parts, some oil, some time....and that lasts 10 days. And that what, do it again. Also, regarding that we are talking about brake components, you are also risking while riding! So, you are buying a product that is not a complete product, actually. I mean, rubber seal that was supposed to drive the DOT4 oil REACTED with that oil, and gets destroyed in 10 days. I will get the refund, but its not the point.

OneLeggedRider · 06-13-2019, 05:54 PM

My last master cylinder rebuild was on my 94 FourTrax 200D. It worked for 2 months and decided to crap out on me going down a very steep and muddy hill out behind my property. And ofcourse the rear drum brake was worthless from the time it left the factory so I hit a tree at the bottom and went sailing over the handlebars landing on a fallen tree on my back. I actually believed my back was broke but then I slowly started moving fingers and toes.

You cannot order a new master cylinder for the old bike so I replaced it with a newer Honda Recon master.

OneLeggedRider · 06-13-2019, 07:15 PM

Quote:

Originally Posted by Megadan

I have rebuilt several OEM Honda Master Cylinders with great success, The bore is critical though, and if it has any damage it is usually best to get another one.

As far as those seals, they were trash to begin with.

And Dan I'm glad you've had such good luck with rebuilding them, but after the near death experience I had I wont be rebuilding any more.

Also I wonder, did most of those cylinders need rebuilt because they wore out, or from lack of use. It makes a difference as far as the bore is concerned.

NzBrakelathes · 06-13-2019, 08:17 PM

New masters are cheap hence the lack of quality
I was paying just over a $1 per repair kit and yeah what can you expect
They are 1/2 inch common seals etc
A decent master cylinder costs a bunch more - better use a known brand

Megadan · 06-13-2019, 08:46 PM

Quote:

Originally Posted by OneLeggedRider

Also I wonder, did most of those cylinders need rebuilt because they wore out, or from lack of use.

Both. Some sat a long time and needed new rubber bits, otjers were just worn out. The ones that I didn't rebuild just got replaced. All of the ones that did get rebuilt got OEM parts, which cost more than a cheap aftermarket unit. The condition of the bore is critical, and if it was damaged at all by the cylinder making contact, then even the best parts will only live on borrowed time, even if the cylinder is honed.

Wild Dog · 06-14-2019, 12:54 AM

Quote:

Originally Posted by Kivi

Also, this brake pump assembly has a nicely positioned thread for the rear mirror, few cm in front of handlebar.
So, I would like to keep the original brake assembly. I dont like to replace whole parts that served me well in the past with parts of unknown quality.

Like you said the part served you well. Now it's worn out and it's a nice chance to change it to a japanese part.

Guess what, the nicely positioned thread for the mirror, is not a chinese desing. I know shocking...
Like always they cloned an Honda product, if you search for CB250 master cylinder you will find them, sometimes they come in pair with clutch lever housing too.

humanbeing · 06-14-2019, 01:55 AM

Quote:

Originally Posted by Kivi

...But, what happened to these seals?!...

Chinese know those kit maybe shite, so some seller https://item.taobao.com/item.htm?id=562971406296 marked seals are made from EPDM clearly for some reason.

Kivi · 06-16-2019, 04:33 AM

I rebuilt it again with seals from a local manufacturer of brake rubber, seals. It's not leaking and is working for now. We'll see will it last. Thanks!

XDoubleXA · 06-20-2019, 10:43 AM

Quote:

Originally Posted by Kivi

I rebuilt it again with seals from a local manufacturer of brake rubber, seals. It's not leaking and is working for now. We'll see will it last. Thanks!

Ive went through like 3 of these. I ended up ordering a whole other brake assembly.

RedCrowRides · 06-20-2019, 02:08 PM

I wish you the best of luck with the local bought seals , I hope they hold up. That said, I get wanting to keep "OEM parts" but when you are talking Chinese bikes and the iffy quality and as cheap as a better master cylinder assy can be had, I think that overshadows the " Keep it OEM" angle ,there is not a lot of logic in insisting upon keeping a turd a turd, with all original turd parts, when you can make it a non - turd very inexpensively. Not intending to offend but your life depends on those brakes bro ,
no one in the Hospital or Morgue is going to care you kept it all OEM.

06-13-2019, 10:12 AM	#3
2LZ Join Date: Mar 2010 Location: Volcano, Ca Posts: 7,112	That's ridiculous. Thought about buying an entire new assembly? They're cheap. https://www.amazon.com/HIFROM-Replac...ateway&sr=8-15 __________________ "Light a fire for a man, and you heat him for a day. Light a man on fire, and you heat him for the rest of his life." 2007 Suzuki DRZ400S (SM convert) 2009 Q Link XP 200 1967 BSA B25 250cc Starfire 2022 Royal Enfield Interceptor 650 2023 Royal Enfield Scram 411 1948 Royal Enfield Model G 350
	0

06-13-2019, 03:17 PM	#5
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,110	I have rebuilt several OEM Honda Master Cylinders with great success, The bore is critical though, and if it has any damage it is usually best to get another one. As far as those seals, they were trash to begin with. __________________ Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124
	0

06-20-2019, 02:08 PM	#15
RedCrowRides Join Date: Jun 2018 Location: Florida Posts: 759	I wish you the best of luck with the local bought seals , I hope they hold up. That said, I get wanting to keep "OEM parts" but when you are talking Chinese bikes and the iffy quality and as cheap as a better master cylinder assy can be had, I think that overshadows the " Keep it OEM" angle ,there is not a lot of logic in insisting upon keeping a turd a turd, with all original turd parts, when you can make it a non - turd very inexpensively. Not intending to offend but your life depends on those brakes bro , no one in the Hospital or Morgue is going to care you kept it all OEM. __________________ 2001 Mustang GT 2004 Sportster 2018 VADER 2020 Orion RXB250L
	1

06-13-2019, 04:09 AM	#2
Kivi Join Date: May 2017 Location: Serbia Posts: 217	I am shocked what happened to the piston rubber seals! The seals on the new kit from AliExpress enlarged and deformed! This is why the return of the lever was so slow, and this is why the lever was sinking to the end without enough brake power. But, what happened to these seals?! I used dot4 fluid, I have rebuild brake pump enough times to know how to do it. Repair kit may be of bad quality. The original (old) kit lasted 15 years with no problem or rebuild! The new one lasted 10 days?!
	0

06-13-2019, 11:08 AM	#4
OneLeggedRider Join Date: Nov 2018 Location: Stockport, Oh. Posts: 1,442	Look at the poor casting of the piston, I'm surprised that it even worked for a week and obviously the seals weren't meant to stand up to brake fluid. Even on a jap bike rebuilding the master usually doesn't work because the cylinder itself is worn. Just buy a new one, brakes are too important to skimp on.
	1

06-13-2019, 05:40 PM	#6
Kivi Join Date: May 2017 Location: Serbia Posts: 217	I like to keep original equipment on this bike, up to a certain point. Some of the parts on this bike, I'm sure, are of very good quality, comparable to Japanese. Not all, through. One example is when I fall once on the right side, hit the rear view mirror hard. Bent the steel chromed mirror holder while aluminum brake and mirror holder (thread m10) survived. Not the best example but you got the point. I can get cheap Chinese complete brake pump from here for 15$, but, how are the quality of their rubber seals? Is it the quality like these rubber seals from AliE.?! Also, this brake pump assembly has a nicely positioned thread for the rear mirror, few cm in front of handlebar. So, I would like to keep the original brake assembly. I dont like to replace whole parts that served me well in the past with parts of unknown quality. I will always try to rebuild. Im not sure if the bore is ok. The new seals from Ali haven't leaked at all if that is relevant. I will try to examine the bore, maybe take a photo, but it would be hard to capture. But, I wanted to point users about the quality of SOME goods from AliExpress. You wait upto 40 days for the order to arrive, you spend some effort to replace the parts, some oil, some time....and that lasts 10 days. And that what, do it again. Also, regarding that we are talking about brake components, you are also risking while riding! So, you are buying a product that is not a complete product, actually. I mean, rubber seal that was supposed to drive the DOT4 oil REACTED with that oil, and gets destroyed in 10 days. I will get the refund, but its not the point.
	0

06-13-2019, 05:54 PM	#7
OneLeggedRider Join Date: Nov 2018 Location: Stockport, Oh. Posts: 1,442	My last master cylinder rebuild was on my 94 FourTrax 200D. It worked for 2 months and decided to crap out on me going down a very steep and muddy hill out behind my property. And ofcourse the rear drum brake was worthless from the time it left the factory so I hit a tree at the bottom and went sailing over the handlebars landing on a fallen tree on my back. I actually believed my back was broke but then I slowly started moving fingers and toes. You cannot order a new master cylinder for the old bike so I replaced it with a newer Honda Recon master.
	0

06-13-2019, 08:17 PM	#9
NzBrakelathes Join Date: Jun 2016 Location: Hell Posts: 2,408	New masters are cheap hence the lack of quality I was paying just over a $1 per repair kit and yeah what can you expect They are 1/2 inch common seals etc A decent master cylinder costs a bunch more - better use a known brand
	1

06-16-2019, 04:33 AM	#13
Kivi Join Date: May 2017 Location: Serbia Posts: 217	I rebuilt it again with seals from a local manufacturer of brake rubber, seals. It's not leaking and is working for now. We'll see will it last. Thanks!
	1