clutch slip - is it the slipper clutch?

R

robin1

Joined Jul 2008

18 Posts | 0+

London

Discussion Starter
• Oct 2, 2008

• #1

Hi

I've just finished a Streetfighter based on a 99 RSV. I've had several before, and not come across this problem before. As I let the clutch out and open the throttle to pull away, the clutch goes soft, and it's hard to control. Also the clutch can be made to slip under hard accelleration, if you try hard enough.

I wonder if the slipper clutch is engaging at lowish throttle opening and lowish revs, instead of just when over-revving as intended. I've changed the engine, so I may have plumbed something wrong, though I had a working Tuono to copy. Or is there a component that could have failed?

I thought I might try isolating the slipper clutch by blanking off the air tube that goes into the casing, but haven't tried that yet.

Any suggestions welcome.

thanks, Robin

 

supertedlover

Joined Mar 2008

3K Posts | 0+

Lincolnshire

• Oct 3, 2008

• #2

I far as am aware from my limited knowledge (spoonz or cat are your men) , if you block the breather the clutch will definitely slip, is it slipping at low or high revs? The early milles had a fault with the clutch cover where is wasnt machined properly this put high spots in the plates making them slip, i swopped my cover and put in new plates (both steels & friction) and it stopped it from slipping, my problem was mid rev range 3/4/5 gear. Hope this helps and am right :thumbup

 

L

LEGS

• Oct 3, 2008

• #3

Also make sure you've bled the clutch correctly. It's easy to leave air in the clutch line if it's not bled correctly. See here for the correct procedure. Also check the clutch slave cylinder is not leaking fluid

http://www.apriliaforum.com/forums/showthread.php?t=15500

Also test the one way clutch vacuum check valve is working ( blow through one way only ) and is mounted the correct way round, arrow pointing up i think. This is located on right hand side of engine on a large vacuum hose from the throttle bodies to the clutch housing and is a plastic cylinder about 2.5 inches long. These regularly fail on early bikes.

Clutch plates do wear out, so it may be a simple clutch plate replacement but check everything else first

 

J

Jussi

• Oct 3, 2008

• #4

Or do not do like me...

changed the lever and was too eager to adjust the lever with the push rod.
This caused saome slipping in odd places. A few turns of the push rod anti clockvise and problem solved.


One needs to learn a lesson...

 

supertedlover

Joined Mar 2008

3K Posts | 0+

Lincolnshire

• Oct 3, 2008

• #5

Thanks legs, i myself will check that valve, is it just a one way valve like for a screen washer or is it more technical? Cheers ST

 

caterpillar

Joined Apr 2008

1K Posts | 0+

Sunny Bournemouth

• Oct 3, 2008

• #6

supertedlover said:

(spoonz or LEGS or fusebox are your men)

Click to expand...

Ahhh, now that is better :biggrin

Silly question, but being a back to basics type, what oil are you running? :dunno

 

L

LEGS

• Oct 3, 2008

• #7

Thanks Cat :thumbup

Superted, it's a simple reed type valve that has a rubber insert that can split. You'll notice the "slipper clutch" not working correctly when you change down the gearbox. You'll feel the rear end hop. Just remove the valve from the hose, pull carefully both ends of the rubber vaccum hose off, noting the way the arrow points on the valve. To test just simply blow down the valve. If you can blow through from either end then the valve has failed. They are about £8.00 from Aprilia. Mine failed last year in the french alps which as i've said caused the back wheel to start hopping on down changes If the valve has been put on the wrong way round it can cause the clutch to slip

 

Last edited: Oct 3, 2008

supertedlover

Joined Mar 2008

3K Posts | 0+

Lincolnshire

• Oct 4, 2008

• #8

Sorry Legs mean to edit that, my back end has been locking up on downshift cos am shifting too quick, feels good, am interested in the thread cos i think my clutch is stll slipping sometimes and i think its the breather, i am getting what i think is a lot of oil coming up the tube, enough to show on the frame

 

S

spoonz

• Oct 4, 2008

• #9

Don't forget the slipper is Vac fed so needs high vacuum to function. Even then it's limited in it's operation.

If you use rev matching on your down shifting then you will have very little vacuum and therefore little slip. High vac needs a closed throttle.

 

R

robin1

Joined Jul 2008

18 Posts | 0+

London

Discussion Starter
• Oct 5, 2008

• #10

one way clutch vacuum check valve was the problem

Hi

I checked the one way clutch vacuum check valve, and it was faulty (could blow both ways through it). I've swapped in a new one (lots of bits hanging about), but not riden it yet. I'm sure this will fix it, but it not I will post again. Thanks for the help. P.S. the arrow should point up to the throttle bodies.