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she's an '09 Brutale with Brembo clutch and brake radial mc's.. OEM slave cylinder. The bike had 4200 miles on her when I bought her in December. The clutch didn't seem to fully disengage until the lever damn near hit the bars, so I bled the m/c and it was much better.

The engagement/disengagement seem to be a bit rough again ( same feeling/issue rising) so i'm gonna bleed the system again before work.

Question is : Is this a sign that the slave cylinder itself is somehow allowing air into the system (leak) although I have no evidence of fluid leak or loss?


..... BTW it's a fantastic excuse to buy an STM slave cylinder

Any insight appreciated,
L.B
 

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Hi Matt/Matthew ?
That's as good an excuse as you might ever need.
On a serious note though, most of the time the leakage is not evident from the outside, with the fluid leaking into the front sprocket area instead.
 

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she's an '09 Brutale with Brembo clutch and brake radial mc's.. OEM slave cylinder. The bike had 4200 miles on her when I bought her in December. The clutch didn't seem to fully disengage until the lever damn near hit the bars, so I bled the m/c and it was much better.

The engagement/disengagement seem to be a bit rough again ( same feeling/issue rising) so i'm gonna bleed the system again before work.

Question is : Is this a sign that the slave cylinder itself is somehow allowing air into the system (leak) although I have no evidence of fluid leak or loss?


..... BTW it's a fantastic excuse to buy an STM slave cylinder

Any insight appreciated,
L.B
You may need a slave cylinder due to air ingress through the seal,but before you spend your money check it is not the master cylinder by-passing.Quick check is move the lever very gently towards the bar.If it creeps slowly towards the bar the problem is the master cylinder.
 

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Mitch, wouldn't that also happen if the slave is leaking by?
 

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Discussion Starter #7
I checked the lever pull and feel.... Smooth all the way through. I think i'll just order a new slave cylinder
 

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I'll give a look at the front sprocket (remove the cover).

... I seem to recall a nice billet aluminum cover I can source as well.

Thanks again!

Cheers

Matthew


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No, just pull the slave cylinder off, make sure you don't pull the push rod out with it.
 

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It's just very hard to tell with the clutch hydraulics...I mean it is designed to go to the bar, unlike a braking system.
 

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It's just very hard to tell with the clutch hydraulics...I mean it is designed to go to the bar, unlike a braking system.
You are right there Chuck.Matthew is loosing his clutch after a period of time,bleeds the system and all is good again,so it is either the slave cylinder is producing air or the master cylinder is by-passing (fluid creeping past the primary cup in the cylinder internally).His fluid level is not dropping.When he removes the slave cylinder he may not see any problem there.Over the internet sometimes it is hard to diagnose problems without physically being there,you can only help the best you can to point him in the right direction.Matthews issue does sound like the slave cylinder is producing air which happens slowly over time with the movement of the piston.Just wanted to eliminate a possible problem with the master cylinder first.Sorry for rambling on.Let us know how you go Matthew.
 

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clutch issues

for some reason the Brembo radial clutch M/Cs eat seals;
from the Aprilia Forum;

http://www.apriliaforum.com/forums/showthread.php?111280-found-radial-m-c-cups/page2&highlight=found+radial+m/c+cups

the Brembo slaves are no prize either;

http://www.apriliaforum.com/forums/showthread.php?132309-improved-clutch-action/page11&highlight=clutch+slave+seal

the real problem is the design of the slave, the cup seal is on the piston.....and as it advances it sees dirty bore.....

should have been a square seal in the body like on a brake caliper.....then it only sees clean piston

and the finish on the bores of both the M/C and slave
 

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So true Noel.They could of also designed a piston with 2 seals,one to scrape the bore clean and the second seal for pressure.I might make some.Second thoughts No,someone might copy it.:stickpoke
 

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Chuck;
Matt said the fluid level wasn't dropping so the M/C primary seal is leaking......clutch system doesn't work very well but doesn't leak

typical Brembo Radial clutch M/C problem on the Aprilia Forum......never happens on the brake M/C go figure?

Matt;
is the fluid dark?

Mitch;
it needs to be like a brake caliper with a square O-ring in the body, the M/C style lip seal is just wrong in this application....

the Aprilias are the worst place to use this type of seal with a spring behind the piston.....the pneumatic slipper clutch jerks the pressure plate back and the slave piston jumps after it sucking air past the rearward angled seal......you know it won't suck fluid through the return port 4' away:wtf:, remove the spring and change the seal design problem solved

the function of the spring in the slave is beyond me

:popcorn:
 

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Noel,the spring behind the piston is required to keep the piston against the clutch pushrod so any kickback from the clutch does not push the piston into the bore.If the spring was missing you would have to pump the clutch lever to take up the gap.Thats how I understand it.:)
 

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Thanks for the info and on-going discussion fellers....:smoking:
 
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