OK, so a pal of mine has rebuilt a 748R. He noticed on purchase that the clutch lever fun point was at average hand span distance away from the bar, but figured that since he was fitting a sparkling new adjustable (different spring options) Ducabike slipper that in the end all would end up fine. Well it ain't, the lever still needs to travel nearly it's full reach before you get any joy. Mainly a problem in 1st, 2nd both up and down. Tried an adjustable aftermarket job but no use. I'm thinking slave cylinder (???) and so he's thinking about getting a Ducabike or Oberon job to fix the problem. Any advice appreciated and yeah I know clutches on the 748 ain't friendly at the best of times but this one is a @#$*^%$ !!
What do you mean by ‘has to travel nearly its full reach’? If you have to pull the lever all the way to the bar to disengage the drive you’ve likely got air in the system and it needs bleeding. Putting an after-market slave on will make that situation worse. After-market slave cylinders increase the lever pull distance in order to make the force required less.
so as though clutch could be on the verge of slipping despite being disengaged? I guess you have already checked the play at the lever when cold? - should be around 3 mm. If this is set at 3 mm when cold but reduces to zero then could be several things but main/popular cause that comes to mind is a partially blocked return port in master cylinder. This runs between reservoir and cylinder bore and can allow system to "pump up" if fluid can't return freely and usually gets gradually worse as things heat up at the slave end.
He might need to check the clutch pack stack height. That situation indicates the stack height may be a little too short. It might be that another thin steel plate will sort the issue
Yes ian, you’re probably right on stack height, as mine is more likely when a vehicle is old and ropey! Had to include it though as often leaves people scratching their heads.
You could try and slacken the little grub screw in the lever where it pushes against the master cylinder plunger, it might be a bit tight.
Addition of an extra dish plate required? It was doing it before and after the install of the slipper. Does sound like a plates issue.
I know what he is complaining about, my 1098s is the same, once you release the clutch the bite is right at the end of the travel. My 996 bites somewhere in the middle of the travel. I find the 1098 frustrating, I think adding a dished plate instead of a flat plate might fix the issue, however I have not got round to it. Was planning replacing the whole lot with a 48T slipper anyway.
The height of the plates relative to the hub is critical with a slipper clutch working correctly... randomly sticking an extra plate is isn’t very accurate. Measuring the stack in the drum and replacing plates to achieve the correct measurement is the better way!
As long as it’s not slipping, surely this is just a matter of lever adjustment. So much better than having the biting point near the grip, so you get drag and can’t find neutral etc
