[Sagani]

Hi Guys,
I have a slight issue with my clutch and thought I would ask to see if anyone could suggest a reason for it.
So I changed my slave for an Oberon and now I have no clutch, if looks like the piston doesn't move enough to push enough of the rod to open the clutch.
I have bled the master over a 20 times and have no bubbles at all in the bleed tube.
The only things I can think of are:
The master cylinder is loosing pressure as a full pull of the lever (to the grip) is only 2.1mm of movement.
There is air or something in the lines (though I have a new slave and I have cleaned out the master)?
The Oberon slave needs a bigger piston that the Nissin 1/2 inch has to move more fluid?

I firstly bled the air from the system which didn't work. I then took the master cylinder apart and checked the seals, cleaned the parts and put back together. Then bled with more new fluid again, prefilling with a syringe from both ends and prefilling the slave before mounting.

When I pump the lever I get good pressure, I open the bleed port and close before letting the lever out......this lever release has no pressure and is very slow to return to its resting position.

Maybe a nice new set of brembo levers are needed

I'm sure I've missed something.
I did try avoiding the garage for a couple of days to see if that would work, I think the Christmas elves were busy doing other things and didn't want to fix it for me.

Over to you guys for suggestions please.

Thanks
Si

 

[silentservice703]

Your Oberon Slave probably has a volume in it larger than the Master can use.
i.e. incompatible parts

 

[mitchy]

You may need new seals in the master cylinder.
How are you bleeding the system?
Try using clear tubing from the bleeder into a bottle with water in it.
Keep the end of the tubing submerged in water .
Pump the lever 3 or 4 times and hold the lever in.
Crack open the bleeder valve and close.
Do this around 4 times, check for air in the bottle of water.
If you still get air you will have to recondition the master cylinder.

 

[Sagani]

Your Oberon Slave probably has a volume in it larger than the Master can use.
i.e. incompatible parts

yeah that was my thinking also. I am in the UK these days so I have sent the oberon guys an email to see if this could be an issue or not.
Thanks

 

[Sagani]

You may need new seals in the master cylinder.
How are you bleeding the system?
Try using clear tubing from the bleeder into a bottle with water in it.
Keep the end of the tubing submerged in water .
Pump the lever 3 or 4 times and hold the lever in.
Crack open the bleeder valve and close.
Do this around 4 times, check for air in the bottle of water.
If you still get air you will have to recondition the master cylinder.

I did think that maybe the seals needed replacing, they did look ok though...... its difficult to mic up a seal to see if its worn.
Everything looked ok tbh. the main and compensating ports were both clear and the seals clean and smooth with no rips.
Bleeding:
I'm pre filling the components with a syringe and then as you have said I'm using the bottle and pipe method. The bottle is 1/3 full of brake fluid.
The end of the tube always in the fluid and as you have said 3 or 4 pulls and open/close release. Zero air bubbles in fluid, pipe or in the master cylinder tank. Even when I let go of the lever suddenly (to shock release the lever and to remove any air trapped in the master) there is still no air bubbles. This was a trick we used to use on classic cars years ago when air was trapped in the master.

Thanks for your help

 

[Tony F]

The larger bore slave cylinders will reduce the amount of pushrod movement available to actually release the clutch so every thing else in the system needs to be right.

Are you completely bleeding the master cylinder? Wherever you are bleeding it from (banjo or bleed nipple) needs to be at the highest point.

From time to time the brembo master on my F4RR will begin to feel soft at the beginning of its stroke so I crack open the bleed nipple and, with a rag in place around it, move the lever through only its first few mm of travel. This will expel an air bubble and then the lever is firm from the very beginning of its movement. I could use a bleed hose to do this but its hardly worth the effort of finding one for what I'm doing.

 

[Trevor68]

I put an Oberon on mine before christmas, they work fine with stock Nissin master, but you only notice maybe 10-15% lighter, more than that and you will want a higher displacement brembo master.
I pre-filled mine with a syringe too, and then used my vacuum bleeder on the nipple to bleed it.
I too wasn't getting any lever, so then I went nuts pumping the lever while also going mad on the vacuum pump and it came good.
I did manage to strip the banjo getting it tight, it seemed to bottom out and I had to use 4 washers to get it to seal (used the originals as well). Since then a new banjo has arrived, which I ferreted away somewhere as I'm too scared to touch it again now it's working.

 

[silentservice703]

One other thing to try is tapping the lever and watching for microbubbles to back into the reservoir. Sometimes it is just a couple of small bubbles trapped in the master return port....

 

[EBBO]

True that, regarding micro bubbles. They hide, they cling, they disperse. You need them to gather. Wrap on the lines. Wait over night. Tiny bubbles move upwards slowly. Having them collide helps. For the Banjo bolt associated to the slave OEM or Oberon I use a combo Stahlbus bleeder. It’s a treat. Highly recommend to avoid stripping and backflow. All my bleeders are Stahlbus from Deutschland. Top bleed radial MC are a game changer but aren’t necessary. Pick your poison. All that said, you have air more than you might imagine.

 

[Sagani]

True that, regarding micro bubbles. They hide, they cling, they disperse. You need them to gather. Wrap on the lines. Wait over night. Tiny bubbles move upwards slowly. Having them collide helps. For the Banjo bolt associated to the slave OEM or Oberon I use a combo Stahlbus bleeder. It’s a treat. Highly recommend to avoid stripping and backflow. All my bleeders are Stahlbus from Deutschland. Top bleed radial MC are a game changer but aren’t necessary. Pick your poison. All that said, you have air more than you might imagine.

That's all good advice thanks. It looks like I'm off the the garage to start looking for micro bubbles and move stuff around make those into large bubbles.
I'll see if I can get hold of a stahlbus bleeder to make it more reliable in the future.

Thanks to everyone for their help so far. I will give it all a go and stop myself from buying a pair of radial Brembo's......
I can't promise I won't be back asking for the best sized RCS piston for a clutch though 😂

Thanks again and I'll report back!

Si

 

[Trevor68]

16 is quite popular, though I see one mob selling 17, which I presume would be a bit lighter.

 

[falcn]

I have the Oberon on my 990R, no such issues for me. I use a pneumatic venturi bleeder. No need to pump pump pump the lever.

Pneumatic Brake Fluid Bleeder with Auto-Refill Kit

Amazing deals on this Pneumatic Brake Fluid Bleeder at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

One of the most used tools I have ever bought.

One thing you can do is buy a new banjo for the master cylinder that has a bleeder in it. Makes the job easier. I go this route now on my bikes after having some masters with a bleeder. It's game changing to have that top bleeder.

Such as this Spiegler Bleeder Banjo Bolt - RevZilla

If you didn't have a problem with the clutch slave before the swap, I would not suspect the mc seals. But now that you have pulled the mc apart they may be suspect. 😬 You'd see fluid coming out from the plunger post the seals. I just had a bad master last season in my track bike and caught the fluid getting past the seals. Those seals looked great upon inspection. I went with an Accossato radial master on that bike. The one that leaked was a brand new Brembo. This is the 2nd Brembo mc that was bad on me. Personally but using them again if I upgrade. I will use the Accossato.

 

[Sagani]

I have the Oberon on my 990R, no such issues for me. I use a pneumatic venturi bleeder. No need to pump pump pump the lever.

Pneumatic Brake Fluid Bleeder with Auto-Refill Kit

Amazing deals on this Pneumatic Brake Fluid Bleeder at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

One of the most used tools I have ever bought.

One thing you can do is buy a new banjo for the master cylinder that has a bleeder in it. Makes the job easier. I go this route now on my bikes after having some masters with a bleeder. It's game changing to have that top bleeder.

Such as this Spiegler Bleeder Banjo Bolt - RevZilla

If you didn't have a problem with the clutch slave before the swap, I would not suspect the mc seals. But now that you have pulled the mc apart they may be suspect. 😬 You'd see fluid coming out from the plunger post the seals. I just had a bad master last season in my track bike and caught the fluid getting past the seals. Those seals looked great upon inspection. I went with an Accossato radial master on that bike. The one that leaked was a brand new Brembo. This is the 2nd Brembo mc that was bad on me. Personally but using them again if I upgrade. I will use the Accossato.

Excellent info thanks. I have a new stahlbus bleeder on its way to me at the moment.
I have left it all alone for a few days to save my nerves 😜
I've turned my attention to drinking instead lol.
I will look into what you have suggested also. I believe I have a pneumatic bleeding system somewhere for the classic cars that I used to restore. Finding that should be fun, probably easier to buy another!
Thanks again all, I'll keep everyone posted and try not to buy lots of new things during my drinking 😀
Si

 

[EBBO]

Stahlbus will do you well. Just last night after a New Year ride Stahlbus bleeders were put to use. They are so simple and brilliant to use. Checking for air is simple as wiping dust off your rims. Really, it’s relaxing yielding immediate results from clutch, to front brake system to rear. Finished without mess or fuss.

Edit;
No vacuum system needed.

 

[Trevor68]

I have this one, which has been very good at getting stubborn systems bled.

Brake Bleeder and Vacuum Pump Kit (harborfreight.com)

 

[Sagani]

Hi All
Ok well I have had another go at bleeding the clutch slave (stahlbus bleeder installed and is very good) but still not opening the clutch. I put around 1.5 litres through it.

I checked the slave and made sure the ball bearing was in the hole.
Prefilled the slave with fluid.
Installed the stahlbus bleeder
Filled the Master Cylinder
went through the stahlbus manual letter by letter
once the air had stopped I closed the stahlbus bleeder valve and had a few pulls of the lever. feels ok.....
Still no clutch.
Ok so I placed a tube and a large syringe onto the stahlbus bleeder and opened it this time 1.5 turns (so the non return valve/ball isn't engaged) then I vacuumed the fluid through to the syringe, no air in the syringe tube....closed the stahlbus bleeder and tried using the clutch again. Nope

So its got to be the lever end (ports or seals) or something after the clutch slave (though it was working before the change. I have no external leaks from the master cylinder and no air coming up through the fluid reservior.
The only thing that has changed is :-
the Oberon Slave........ oberon has said they don't have any known issues when using the standard Nissin lever and their slave.
The fluid change...........maybe something in the master gave up during the fluid change?

Either way I'm bored of trying and think I'm going to start replacing parts until it works. Brembo, Accossato, Performance Tech??

Time for a beer now and I will try one last time tomorrow afternoon before I get myself some radial masters.

If anyone wishes to suggest anything, including opinions on radial masters etc (Thanks for the info about Accossato Falcn ) then that would be most appreciated.

Thanks for the help so far, I'm very grateful for everyone's time and effort on this small issue I'm having

Si

 

[EBBO]

GaleSpeed Elaborate brake and clutch work well with Nissin and Oberon. Pricey tho. I can send pics and specs, just laid up right now in recovery. If you end up going that route then two more bleeders will aid for top air release. Surprises me always how much gets cleared through the top. Operation wise the pull is smooth as butter. Brake is no more than a finger or two. Great feel. Adjustable pull depth. Take the install process to clean pistons the brake and apply brake specific grease. Further down the performance rabbit hole. Turned my disc setup into full floaters front and back. It’s a noisy venture but a game changer with Alth rotors and dual carbon pads. BrakeTech floating rear is iron blend. Conversion of current rotors can be achieved via Performance Parts out of Deutschland. Button conversion from semi to full using stock rotors. You’ll have to check on product compatibility.

 

[EBBO]

I try to get up to snap a few photos to help visualize. Bare with me…

 

[silentservice703]

Um, before you go shooting money at it, restore the system to original and see if it works if I dies not work in original configuration, then the issue is downstream of the slave.

 

[silentservice703]

Did you change levers?