Warning lost all front brakes after this !!

[Old Rider]

I have to put out a little warning and my experience with yambits parts  

The last days i have several times experienced too lose all brakingpower on front calipers both sides and the brake lever travels all way into handlebar.
It is an unpleasant feeling .The strange thing is the brakes works just fine with a firm lever most of the time.It is not like i have to pump the lever
to get it to work it just sometimes just get completely lose with no resistance and no frontbrakes.I was thinking since i done a little vertical riding the last days maybe some air had got trapped or something ,but my brakes has never got damaged from it before ,so first i bleed the brakes ,but just some tiny bubbles was coming out.I took a ride and the same happend a few times lost all brakepower in front from time to time but most of the time brake worked perfectly.


Then replaced the brakefluid and bleed the brakes one more time and checked that the vent hole in reservoir was not clogged.Took another ride and Same shit happened god brakes most of time but suddenly no brakes at all  .I discovered that
it was happening mostly if i had not operated the lever for a while and slowly pulling on the lever.


I then checked for any leaks at the caliperpistons and bleedscrews  and at the antidives and at the T split joint behind the horn and at all the banjo connections
no leaks was found. and the went hole in the reservoir was not clogged.Also checked the athmosphere hole in the fillecap on master reservoir lid. with bike parked and with the lever pulled into handlebar i checked the brakepads with my fingers and they could be wiggeled as they should when no brake are aplied  It was a mystery to me since i have been working on bikes since i was a kid and never experienced anything like this.

Then i remebered that last winter i replaced the mastercylinder piston with a rep set bought from yambits uk.I did this just as a maintainece since i also
replaced the master piston rep set on the clutchmaster.When inspected the mastercylinder bore on brakemaster it looked like new no pittings or scorings
so i just mounted the rep set bought from yambits uk. The brakes has worked with no problems the hole summer ,but a few days ago i started to lose all brakepower .

Today i did another try to fix it by losening the 14mm banjobolt on the master with a rag wrapped around it to see if any air was trapped in there,but the same happened when took a little testride .I then tried to get hold of a new master rep kit but it had to be ordered and then i cant ride for many days.I then searched in my spare bikeparts stuff and found a bag with the old used
brakemaster rep set that was  replaced last winter.

I rode up to a place i usually do some work on the bike and pulled out the yambits brakemasterkit that was installed last winter and mounted the old brakemasterpistonkit .I first inspected the new yambits kit that was sitting in the cylinderbore but it looked fine only thing i notised was that the cylbore where it sits was very black like the rubber that is fitted on the brakemasterpiston had smeared onto the bore. I cleaned the cylbore  up a little and then mounted the old kit i took out last winter.
I did not even need to bleed the system only a little wiggeling on the brakelever to get the air out

And yes you guessed right brakes now works perfect again and i have rode for several hours today with no problem.

I found a picture of the parts i bought from yambits uk last winter and will post it here so you dont buy that shit.

[red]

Old Rider,

I am not sure I understand all that you had happening there, but it sounds to me like you were sold some defective parts.  You may need a new master cylinder there.  I hate to say this, but some unscrupulous makers are producing bad merchandise, and labeling it with a reliable brand name.  Sellers may or may not know about the fraud, as they pass it on to you.  I can only say, do not look for the lowest prices on important parts, such as brakes, hoses, and critical fasteners.  Use reputable, well-known sources for these parts.

RPM (owner of this site) has bleeder banjo bolts, which can bleed air easily and cleanly from the vertical hoses at the clutch and front brake master cylinders.  Note: Always use new hydraulic washers when changing banjo bolts, to avoid leaks.

[Old Rider]

Old Rider,

I am not sure I understand all that you had happening there, but it sounds to me like you were sold some defective parts.  You may need a new master cylinder there.  I hate to say this, but some unscrupulous makers are producing bad merchandise, and labeling it with a reliable brand name.  Sellers may or may not know about the fraud, as they pass it on to you.  I can only say, do not look for the lowest prices on important parts, such as brakes, hoses, and critical fasteners.  Use reputable, well-known sources for these parts.

RPM (owner of this site) has bleeder banjo bolts, which can bleed air easily and cleanly from the vertical hoses at the clutch and front brake master cylinders.  Note: Always use new hydraulic washers when changing banjo bolts, to avoid leaks.

Hi Red !  Thanks for your interest in this post i know im not so god at explaining about what was going on when i lost all brakepower but i had no brakes at all on frontwheel several times during last days.Then inbeetween the brakes worked normally.
I found out that the cause of sudden brakefailure was that i had installed a brakemaster cylinder rep-kit i ordered from yambits uk and want to warn other riders that that might
have the yambits brakemaster repkit installed or thinking of buying one.
When i installed the brakemaster from yambits last winter i first inspected the cylinderbore in the brakemaster and it looked like new with no pittings or scoring so i just installed the
yambits repkit .I also instaled a repkit in the clutchmaster cylinder ,but the bore in the clutchmaster had some pittings and had to be honed  i then used a tourmax repkit.I made a writeup on that here : https://fjowners.com/index.php?topic=20077.0 (the clutchmaster and slave is still working fine i used tourmax repkits on those parts)
When i tried to order a front brakemaster repkit last winter i did not find any tourmax repkit (not on RPM website either)  ,but then i found the yambits uk website and that they had a frontmaster repkit .I have no experience with the quality on yambits parts ,but thaught since it was such a important safety part it must be okay. The yambits brakemaster repkit has been working
fine in six mounths ,but as i said earlier it suddenly in the last days has failed and left me with no brakes at all in the frontwheel several times.
So the bottom line is buy a original or tourmax brakemaster cylinder rep kit if planning to do some maintanence on the brakes.I will NEVER buy anything marked yambits again atleast
anything they have with rubber.Seems that the rubber that is used is very bad china quality

[racerrad8]

Just confirming, this kit?

http://rpmracingca.com/proddetail.asp?prod=M%2FC%3AFRTBRKRBKIT

We sell a ton every year and I don't ever recall an issue reported.

Glad you found the issue and you were not injured as a result.

Randy - RPM

[Pat Conlon]

So the rubber seal failed?
The greasy residue in the bore sounds like the rubber deteriorated from contact with the brake fluid.
I wonder what would happen if you put the rubber seal in a sealed jar of brake fluid for a few weeks.

[ribbert]

Rolf, what did you lubricate the seal with when you assembled it?

[red]

Man you gotta love the RPM crew.  It is great to have them as a parts source for our bikes.  Thanks, guys!

I have their Oil Filter Spin-On Adapter on my 1985, so I can use ordinary automotive-type oil filters instead of the messy paper-cartridge Yamaha oil filters.
It is a great accessory, and easy to install.  Just be sure to use oil filters with anti-drain valves in them.  The plain filters will drain out every time you turn off the engine.

[Old Rider]

Just confirming, this kit?

http://rpmracingca.com/proddetail.asp?prod=M%2FC%3AFRTBRKRBKIT

We sell a ton every year and I don't ever recall an issue reported.

Glad you found the issue and you were not injured as a result.

Randy - RPM

Hello Randy it is strange i did not find that kit when i searched your store last time. That is not the same kit as yamabits sell i can see that by comparing them on picktures.
I know RPM only deal with high quality parts and will order it from you this winter.

[Old Rider]

So the rubber seal failed?
The greasy residue in the bore sounds like the rubber deteriorated from contact with the brake fluid.
I wonder what would happen if you put the rubber seal in a sealed jar of brake fluid for a few weeks.

Phather Pat i think you are right .I used the kit since march and it has worked with no problems until the last days it failed to make pressure and the brakes did not work
from time to time not a good feeling =).Maybe the rubberseals just has worn out but in six months ? or the rubber  like you say deteriorating from the brakefluid .
Here is what brakefluid i use never had problem with it damaging seals

[Old Rider]

Rolf, what did you lubricate the seal with when you assembled it?

Ribbert : the yambits kit did not included any lubricants so i think i used only brakefluid or i maybe used the pink grease that was included in the Tourmax clutchmasterkit dont
remember.But one thing i notised when i had a look at the failed yambits kit now is that one of the seal is very loose and is easy to rotate on the masterbrake piston i dont think
it is suposed to do that ?

[Old Rider]

Man you gotta love the RPM crew.  It is great to have them as a parts source for our bikes.  Thanks, guys!

I have their Oil Filter Spin-On Adapter on my 1985, so I can use ordinary automotive-type oil filters instead of the messy paper-cartridge Yamaha oil filters.
It is a great accessory, and easy to install.  Just be sure to use oil filters with anti-drain valves in them.  The plain filters will drain out every time you turn off the engine.

Red : That is absolutly true i only had positive experiences with RPM they have top quality parts and ship fast .And Robert and Randy offer top service !

[RPM - Robert]

dot 5.1 is also compatible with dot 3 and dot 4. Since these bikes used dot 3 I would think the seals used in repop kits would sustain such fluids.

[ribbert]

Rolf, whatever the reason, there appears to be some sort of contamination going on. The gel like sludge and the degradation of the seals are both consistent with fluid incompatibility. I know you showed a photo of the fluid you used (5.1) but is there any possibility that Dot 5 brake fluid played any part in this?

There are plenty of chemicals used in the garage that will turn brake seals soft, even residue from parts washing in the wrong solvent can damage them. I can feel those seals just looking at them.

As for the piston damage, I thought the brake lever had a much bigger contact area (although it's a long time since I've seen one)

The nature of the failure is most unusual.

Noel


Haha, your photos, description and dialogue boxes have got to be the best detailed problem ever!

[Old Rider]

dot 5.1 is also compatible with dot 3 and dot 4. Since these bikes used dot 3 I would think the seals used in repop kits would sustain such fluids.

I agree if the seals not made of some super bad quality.

[Old Rider]

Rolf, whatever the reason, there appears to be some sort of contamination going on. The gel like sludge and the degradation of the seals are both consistent with fluid incompatibility. I know you showed a photo of the fluid you used (5.1) but is there any possibility that Dot 5 brake fluid played any part in this?

There are plenty of chemicals used in the garage that will turn brake seals soft, even residue from parts washing in the wrong solvent can damage them. I can feel those seals just looking at them.

As for the piston damage, I thought the brake lever had a much bigger contact area (although it's a long time since I've seen one)

The nature of the failure is most unusual.

Noel


Haha, your photos, description and dialogue boxes have got to be the best detailed problem ever!

Noel : im sure i used the yamalube dot5.1   i found some picks from last winter and you can see the adjuster screw contact area it is rounded .
I like details   and here are some more detailed photos i found from when i installed the yambits brakemaster rebuild kit last winter