Evo 250 Clutch

[trapezeartist]

Having ironed out all the other problems on my new-to-me 2014 Evo 250, my one remaining issue is clutch drag. I dropped the oil level to the bottom of the window and did the “Beta clutch fix”. No change.

On closer inspection of the master cyl and lever, I realised that the clutch frees off if pulled in hard against the grip, but under normal riding my middle finger is trapped under the ball-end and stops the lever travelling that far. The lever is adjusted to have less than 1mm free play at the pushrod. However the rod inside the master cylinder moves about 3mm before the load becomes significant, presumably because it has to move that far before it starts pushing against the clutch springs. Is all this normal?

At the moment the lever is Apico, but it looks about the same shape as standard. Is there a lever available that curls forward far enough to leave room for my middle finger? Or should the clutch fully disengage with less lever movement?

[lineaway]

I am thinking you have not enough free play, so the piston is not traveling far enough. You can take the M/C cylinder lid and inspect the movement by the holes that feed fluid to the piston. Usually with the lid off it will push a little fluid almost airborne. This would be a good time to just take the lever off and pump it with a screwdriver. I bet you get some air out of the system.

[trapezeartist]

8 hours ago, lineaway said:

I am thinking you have not enough free play, so the piston is not traveling far enough. You can take the M/C cylinder lid and inspect the movement by the holes that feed fluid to the piston. Usually with the lid off it will push a little fluid almost airborne. This would be a good time to just take the lever off and pump it with a screwdriver. I bet you get some air out of the system.

I had wondered about air in the system, though the transition from the 3mm of almost free movement to proper actuation is quite abrupt. Not like compressing air. What is the best procedure for bleeding the clutch?

[lineaway]

 Same as above.

[trapezeartist]

There was absolutely no air in the top of the system so I checked the bleed nipple on the slave cylinder too. None there either.

I found I could adjust the return stop out a little bit to move the lever away from the grip. After re-adjusting the pushrod to suit I gained a little bit of extra travel and that’s just enough for the clutch to clear properly. I could do with a bigger left hand now though.

I realised while poking about that the 3mm of easy motion in the master cylinder is the movement before the piston covers the drilling’s from the reservoir. I’ve pushed the adjustment to the absolute limit to get the maximum piston movement. It seems OK in the garage but the final proof will be in the trial on Sunday.

[dan williams]

So you're saying you have 3mm travel of the pushrod before it engages the throw-out bearing. That's a little odd since the mechanism is meant to be self adjusting. It sounds like somebody reassembled the actuation mechanism without the ball bearing that goes between the push rod and the shaft of the throw-out bearing. See parts 19, 20, 21.

 

[trapezeartist]

2 hours ago, dan williams said:

So you're saying you have 3mm travel of the pushrod before it engages the throw-out bearing. That's a little odd since the mechanism is meant to be self adjusting. It sounds like somebody reassembled the actuation mechanism without the ball bearing that goes between the push rod and the shaft of the throw-out bearing. See parts 19, 20, 21.

 

Terminology! I meant the pushrod in the master cylinder. Not the pushrod from slave cylinder to clutch.

Un fortunately I won’t be testing the result in action tomorrow; crocked my back!?

[dan williams]

Ouch, sorry to hear that. Hope your back gets better soon.

There is one odd thing that has happened to me with the master cylinder. I once damaged the internal spring in the master cylinder in a crash. This caused the lever not to return properly and made for some funky adjustment. It's rare but it can happen.

[trapezeartist]

That’s a bit interesting, Dan. Both the rubber gaiters were split so I got replacements. The kit included the outer pushrod (that word again!) and the spring. I didn’t have springs and didn’t know I was supposed to! It was easy enough to work out where they went, so now I have them fitted.

[dan williams]

Have you got the clutch sorted yet? Inquiring minds want to know.

[trapezeartist]

I think so, but due to other activities getting in the way I won’t be out on the bike until next weekend. It certainly feels much better when I try it in the garage.

If it Is cured, it’s down to adjustment at the lever/master cylinder. I found I was able to let the lever out much further than expected so there is now more travel before I trap my othe fingers against the handlebar grip. It should be enough although it’s now a bit of a stretch for my fingers.

I still can’t help feeling that a short clutch lever would be a great help. Something like the two-finger levers they put on mountain bikes. Then the unused fingers would be beyond the end of the lever and not getting in the way.

[dan williams]

I used to use the shorter levers but now I use the stock levers with the perch in as far as it will go. Gives more leverage to reduce pull and also makes it less likely to break a lever in a fall.

[guy53]

That's what I did with my levers, the reason I did it was to help me with control. It worked for me.

Guy

[lineaway]

 I am going back to the guys that seem to know what they are doing. My shims should be in Tuesday, http://wise-motosports.ocnk.net/

 

Edited March 23, 2019 by lineaway

[thall1]

what do the shims do for the clutch?