Motorcycle Repair: Clutch issues

Question
QUESTION: 2001 Aprilia RST 1000 Futura

Firstly, the engine oil was slightly low for a couple of weeks now and the clutch was starting to act a bit funny about 10 days ago when it used to have minor pulsing attempts to ‘move’ when I was standing with clutched pulled in at first gear. It didn’t actually move but I could feel it. Not sure if oil is a coincidence or causation.
Last Saturday I went to Leicester where it got there fine without anything funny. Next morning I started up and I could hardly back up with the clutch pulled in to get out of the parking spot. As I hit the motorway I realised its getting progressively worse and I assumed its low clutch oil, as I’ve always constantly had to top up even after I got a new slave seal. So I thought it’s the same thing, pulled over and bought a bottle of new DOT4 oil.

Now I couldn’t get moving at all, as there was no disengagement. Got to a slope and had a very clumsy, noisy gut wrenching rolling start and got all the way to a few miles from home and got a red light. Same thing had to find a slope to roll-start and get home.
Forward to today morning I had a replacement slave/piston/seal from an almost new RSV1000 mille (same clutch system) as it seemed logical that the problem has something to do with the fact that I’ve always had to keep topping up clutch fluid and that the piston was worn and that changing the whole thing would make sense. I spent the day changing it and it’s exactly the same.
The interesting thing is that it has FULL PUMP ACTION AND RESISTANCE, not like when you have an air gap. Also sometimes, before the lever gets to the handlebars it sometimes hits a limit where there is suddenly very high resistance, like it hits a block of metal. Even when I squeeze it past this point all the way to the handlebars the clutch does not disengage at all.
Is something binding mechanically? That deteriorated due to low oil? Or is it still the dodgy clutch line where I need to change the whole thing from master to slave - hoses and all?

ANSWER: Hi Tavish,

It sounds like you have the slave cylinder working so the next things
to check would be the slave push rod that goes through to the
clutch. If it is worn or bent somehow that would be a problem.
If the slave cylinder and the push rod are okay then the
clutch plates or discs might need checking for warps.

If the steel plates have been very hot they may have warps
in them that would cause a grabby or sticking clutch.

If you have the clutch cover off you may be able
to pull the clutch lever and watch if the clutch
is moving to separate the clutch plates.

The clutch slave moves the clutch push rod against the clutch springs
holder to cause the clutch plates to separate and slip for disengagement.

If the slave and push rod are working the clutch plates will separate
very slightly and allow the clutch to slip. If the clutch plates are
warped then this movement will not be enough.
If that is the case you will have to disassemble the clutch
and check all the plates for burning, warps and wear.

Here is a link to a page with info and some specs on plate warpage etc:
http://home.comcast.net/~sl_mille/clutch.html

If you find the push rod is not moving the clutch then you might
need to check the slave and the clutch line above the bleeder
and the push rod itself for problems.

IF your clutch is working you should be able to put the bike
in a higher gear, pull the clutch and turn the back wheel
then watch the clutch plates slip as you turn the wheel.
The plates should move apart slightly and then the wheel
should be able to turn without turning the engine.

If the slave is not moving the push rod then you still have
slave problems or line blockage.

Wayne S
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---------- FOLLOW-UP ----------

QUESTION: Just a follow-up since you were helpful. The pushrod bearing had snapped

Have a look here..

http://www.apriliaforum.com/forums/showthread.php?281864-Clutch-won-t-disengage-

Thank you so much!

Answer
Hi Tavish,

Those long push rods have been a problem in many bikes, Yamaha
has used them as well and sometimes the end will break off.
I have replaced a few and also the very old Harleys had a troublesome
push rod and bearings arrangement on the clutch.
I thought you might find something there if you took it apart again.
I hope there is no other problems so you can get back on the road soon.

Cheers!
Wayne S
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