I'm not sure that you will broaden the 'engagement' zone as that is a function of clutch friction & deflection. You will add more clutch lever travel so you will have more hand movement to get to the engagement zone & you will have move hand movement through the engagement zone . You will also have more lever movement on each shift so that will change the shift to clutch timing.
I think my wording could have been better. I agree that what would happen is add more clutch lever travel
. That is my goal [and reducing lever force]. I just find it easier to pull out of sand, etc. [For a demo, watch this] https://www.youtube.com/watch?v=Yx4vABlSpp0
I am aware of running out of lever travel. My fabricated pulley system for the old R100 [1/2 lever force reduction, 1/2 pressure plate movement] almost ran out of lever travel. In fact, the clutch did [does] drag a little. [Still less than ALL wet clutches do.] This time I would probably go for a 30% force reduction, which I calculate is a 27.3mm slave piston. So somewhere around 27 or 28 would be about right.
I thought about off setting the pivot in the clutch lever. Eccentric bushings. I remember thinking that was impractical! [Like fitting a different slave cylinder IS PRACTICAL!] I should make some measurements. I suspect a 1 or 2 mm off set might do it. I going to investigate that more thoroughly. I'll post if there is anything worth while. Lowndes
sezThere is a rather close fitting housing for the slave cyl as part of the rear tranny housing. See pics. You may have to bore that out to fit a larger slave cyl and that would be a project.
I thought about boring out the hole for the slave. Depending on the size of the slave cylinder, the wall might not be thick enough. That is where the adapter plate comes in. The plate bolts to the transmission, the slave bolts to the plate. Different bolt hole patterns and spacing. The slave wouldn't project into the transmission. This thread about a different, larger slave is about finding out if someone has done it or knows of it being done. The pulley system on my old R100 is a known modification.
Why re-invent the wheel? [Figure out what someone else already has.]
My '99 R1100S slave cyl failed and the DOT4 ate up the clutch and the tranny seal next to the slave. While you are in there I'd recommend drilling a weep hole in that slave cyl housing to prevent killing your clutch when the slave piston fails.
As far as a weep hole WHEN
[your word choice]slave piston fails, I'm down with that. My slave has yet to fail, but the transmission seal has! And of course, I only discovered that when the clutch started slipping. The way I see it, the only way to drill a hole there is to remove the trans. I see in your photo the trans is out of the bike. My [interim] solution was to slot the gasket. I was able to attach a shop vac to the trans rear [slave removed] and suck most of the oil out of the push rod hole in the shaft. I then removed the starter, bind the clutch lever to the grip, select a gear, turn the wheel to rotate the clutch while simultaneously spraying 1/2 can of carburetor cleaner at the clutch/pressure plate interface. Now the clutch doesn't slip too bad. I haven't really ridden too much and am expecting a replacement in the future. But it may 'heal'. The clutch on my old R100 has slipped for more than a decade [175,000 total miles on the clock], so maybe a happy ending? Right now I am building a fairing, switching shocks, making seats, yadda, yadda and will probably maybe might disable it in the distant future to lube/replace transmission splines, swing arm bearings, final drive bearings, drive shaft bearings and what ever else goes wrong with these bikes.
Beemer Bone Yard has smaller piston slaves. Wrong direction. I want bigger.
Thanks for your comments.