M900 Clutch Help

Hi guys,

So I've done a bit of a clutch overhaul on my 93 M900, but I have a feeling that something is not quite right.

I've installed a Barnett clutch basket off a 1997 M900 that I used to own, as well as the plates from it which had very little use. I've also installed an Oberon slave cylinder, with the little insert on the pushrod, and I have a new master cylinder and lever on it too.

I've bled the system and I'm getting pressure - the handle feels fine. I'm able to go through the gears but when I pull the clutch in when in gear the pressure plate rotates and grabs the stack when I move the bike - I can't remember if is supposed to do this. I dont think it should.

Can someone please tell me if this is normal? Or if not, where is the first thing to check?

Thank you!

[Mr Gazza]

The first thing to check is the bleeding. Those clutch systems are proper bar stewards to bleed, you think you've bled it properly and then......No!

If you lift the lid off the res and just caress the lever a little you can sometimes see a little stream of tiny bubbles rise from the filler hole.

So have another go at bleeding it... They get you every time!

Thank you! I had a feeling it might be this or push rod length. I will try to bleed again and see what happens!

Do you know what the stack height should be? I think I've read 38mm?

[Mr Gazza]

Yes stack height should be around 38mm. I little less doesn't hurt too much but more can cause problems.

There is quite a bit about pushrods on this thread if you're prepared to wade through it as it bifurcates into to two subjects. See posts #47 and #57 on page four. http://www.ukmonster.co.uk/monster/s...g+oberon+slave

Your pushrod should be 325 mm long and should be used with the 10mm spacer.

You will have "anti-rotation slots" in your slave and so you could convert to an anti-rotation pushrod which is 335mm long and would be used without the spacer. Part No. 11721122A.

The clutch end of the pushrod needs to be all in good order too, so the top hat that the pushrod sits in needs to be clean and lubed with a little grease. The thrust bearing needs to be good too. They're very cheap and should be replaced routinely.

You also need to observe that the pressure plate is correctly installed with the arrowed (a big triangle actually) spring hole, positioned over the spring post with the slot. (it looks like a screwdriver slot.)

You may have a wear in the outer drum which is making the plates stick in the grooves? this will have a serrated appearance to the drum slots which the plate tangs engage in, you might also have burrs on the plate tangs? There's not a lot you can do about that except replace the drum and plates as filing the serrations and burrs just accelerates the wear.

Back to basics: it's a very good idea before you reassemble the clutch, to wash all the plates in clutch and brake cleaner to remove oily residues and dust. This alone can often transform a clutch.

Hope that helps.. Let us know how you get on.

Thank you!

It's a new DP pressure plate, so the bearing should hopefully be fine! I dont think I greased the cap end of the push rod though so I'll make sure to do that. I'll also double check the stack height as it has been changed. I checked the little arrow lined up with the slot when I fitted the pressure plate.

The basket is basically new and the drum looks ok, the plates are all spotless too so I dont think it is anything to do with interference or sticking in between the clutch itself.

I'll double check the push rod length later on (and I'll make sure I did actually put in the spacer!��) but a new, longer push rod might not be a bad idea in the future.

I think it's going to be trial and error like you say, I'll start with checking measurements and I'll grease up the little cap. Then it is on to the bleeding (I would love to avoid doing this again)

Cheers

[Mr Gazza]

Be careful not to over do the grease in the top hat, just a dab is enough to make sure the rod slips through the O-ring in the top hat nicely and it keeps the muck and corrosion out so the rod comes out easily next time off. This is more important if you covert to an Anti-rotation rod, as those have to be withdrawn from the slave side because there is a pin in that end preventing it from going the clutch way.
There's a little hole in the end of the top hat which will produce a little worm of grease as you push the rod in, wipe that away.

I even wash new plates however clean they look, as you can't see the contaminants that make them stick or slip, besides it can't do any harm.

Don't fret about the spacer, I doubt it will work at all without it, so I would be confident that you put it in.

At the end of the day, if it's working okay and not slipping or dragging I would say you don't have any problems. A bit of strange pressure plate rotation shouldn't be over-thought, they do have a mind of their own. Especially if you're just wheeling the bike about with the engine off, it won't be spinning fast enough to separate properly.

[Darren69]

With a lot of these aftermarket slaves, the master cylinders can struggle as they are larger so need more lever travel (fluid) to fully disengage. On mine I have to have the level span adjuster to its largest setting, then it works fine.

Thanks guys. I'll see what I can do.

Are we able to adjust these levers? I might be ignorant here but I dont seem to remember seeing any form of adjustment on them. I bet I was looking in the wrong spot.

So after a lot of tinkering and way way too much bleeding I think its sorted.
I've had to change out some of the friction plates which got me a little closer, then back to the stock pressure plate...almost there but hard to find neutral when running, and it would stall easily.

Then I thought I'd see if there was any adjustment on the lever, like Darren mentioned. All I have is a screw, but it was pre set and filled wax. So I took out the wax, screwed it in by half a turn at a time...and this made all the difference! 4 full turns later and I have a nice clutch movement, I can find neutral and the bike no longer wants to stall easily. Now my only question is does screwing it in this far cause any other potential issues?

[350TSS]

You need to have some free play at the lever end, about 10mm at the ball end of the lever before you feel the actuator rod hit the piston in the master cylinder.
I am not really sure why this is so, presumably to allow for heat expansion, maybe its an "old wive's" carry over from cable clutches.

[Darren69]

Originally Posted by 350TSS

You need to have some free play at the lever end, about 10mm at the ball end of the lever before you feel the actuator rod hit the piston in the master cylinder.
I am not really sure why this is so, presumably to allow for heat expansion, maybe its an "old wive's" carry over from cable clutches.

That was my take on it too, but I wasn't sure on the amount of free play required or how much further back the master cylinder could move due to fluid expansion.

[Luddite]

I don't think the free play is needed to accommodate expansion as any increase in fluid volume due to heat would flow back into the reservoir via the compensating or bleed port, rather than pushing the piston out. The bleed port is small and easily blocked by debris or corrosion if you don't change your fluid regularly. If is does become blocked that can cause brake binding or, in extreme cases, lock up as the fluid expands and has nowhere to go.

Sorry, couldn't find a diagram of a clutch master so you'll have to make do with a rear brake - but the principle's the same.



As long as you have some free play, so you know the clutch is disengaged when the lever is fully out, you should be fine.

[Darren69]

Yea, it's probably more important with the brake than the clutch anyway. You could always upgrade to some adjustable span levers if you were worried.