VIDEO -- of my Aprilia hydraulic clutch mod

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I've completed the hydro clutch mod, I've got a couple hundred miles on it, and it is an overwhelming success.

The Super RustBucket had a pretty hard cable clutch pull. I was never able to get a very satisfactory cable routing. With the hydro clutch, the pull is now about 30% of what it was before. Maybe even less.

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This is an almost 10-year old iteration of my 1976, back in its "Bug Killer" days. Note that the clutch cable makes a gentle, swooping, "S" curve. It's still like that today. You can't get an easier cable pull than this. However, the hydro clutch pulls easier.

Furthermore, the clutch operates like a dream hot or cold, stopped, or moving. Goes in and out of neutral effortlessly in all conditions.

I have one minor tweak I want to try, and then I'll be posting a video I'm making of the installation.
 
Awesome work Dogbunny.
I kind of love how the modification is visible.
I originally was leaning toward the "incognito" style such as MrRiggs but I think I lam preferring the way that set up looks. Something I have had on my plate for much later do figure out.
I will be looking forward to your video.
Outstanding work on one of the xs650's most common problems. Done without great cost, repurposing an existing part designed for another application. Great addition to the vast information contained in this forum and in my opinion should be considered for inclusion into the technical section for ease of searching.
Thanks for sharing!
 
I originally was leaning toward the "incognito" style such as MrRiggs but I think I lam preferring the way that set up looks. Something I have had on my plate for much later do figure out.
I originally would have preferred "incognito." Forum member Bewarethemoon is working on marketing a kit based on MrRiggs hidden slave cylinder, which I would like to try on a different bike.
However, there is one huge advantage to having the slave on the outside of the sprocket cover. Remove three bolts, and the slave cylinder comes off, and you have access to the push rod. This is important because the length of the push rod has to be PERFECT, and it will take a little trial and error to make it so. There are easy ways to make the rod longer if you cut it too short, and of course, you can always make a too long rod shorter. But, when all is done, the rod length should be perfect. A 0.25mm difference in length will have a pretty big effect on "clutch feel" -- how and where the handlebar lever releases the clutch. I've got the feel so that it's just like it was with the cable.
 
Yes I was leaning heavily toward the igcognito style. I had been thinking about it after reading MrRiggs modification. I have also been very impressed by Daniel's (Bewarethemoon) efforts to create a similar system. In fact I think I was about #7 on the order list. The derailment of that project (which thankfully has since resumed) had me once again looking and thinking. Since I am not a machinist, that led me to considering the use of an existing slave cylinder designed for other applications such as the Aprilia you chose, among others. I am just so far from that point that it has been far down the line for me although I have continued with the research. You taking on the exact same project and negotiating the pitfalls along the way to present a solution will save those like myself that have great interest in a usable hydraulic clutch many headaches, much time, and help us produce better results for our efforts. If I were building a resto mod or something similar I would without question prefer the incognito version as well. It is very very cool. Your "how to's" are always first class and very informative. Congratulations on this successful venture!
 
Nice work Dog. This is one mod that I need to do on my bike for sure.
I'd like to see more and longer road testing. Would like to hear from those who have been running it for a long time. But if it passes the test of time, then I think this is one of the best mods that can be done.
 
I'd like to see more and longer road testing. Would like to hear from those who have been running it for a long time. But if it passes the test of time, then I think this is one of the best mods that can be done.
Excited about this. I think I’ll start looking for and engine case for the mod and keep my original. Too bad there isn’t a way of adjusting for the rod length. I guess over time, as the plates wear, the rod would have to be shortened?

May have missed it but what size master cylinder are you using?

Just thinking… for mounting the slave cylinder, one the mounting holes are located, the inside of the case could be built up with weld, then redrilled and helicoiled, that should make the mount quite solid.
 
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Excited about this. I think I’ll start looking for and engine case for the mod and keep my original. Too bad there isn’t a way of adjusting for the rod length. I guess over time, as the plates wear, the rod would have to be shortened?

May have missed it but what size master cylinder are you using?

Just thinking… for mounting the slave cylinder, one the mounting holes are located, the inside of the case could be built up with weld, then redrilled and helicoiled, that should make the mount quite solid.
Some good points and some good questions there. Whenever I finish the video, a lot will be answered. Making a decent vid takes a lot of time and editing.
I'll answer one at a time.
I'm not smart enough to figure out if the rod has to be shortened or lengthened as the plates wear. Two points -- first, the plates take forever to wear. Would probably be ten thousand miles before anything had to be done.
Second.

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(Incorrect slave shown for illustration purposes only.)
If you make the rod too short, you can just drop a round, washer-like shim in the bottom of the piston rod hole. I'm thinking this is the way to go -- make the rod too short on purpose, then drop three 0.2mm thick shims in the bottom of the hole. Remove or add shims to taste.
 
May have missed it but what size master cylinder are you using?
My research indicated that a 13mm bore was popular. I searched eBay for cheap master cylinders. Found a Chinese one from a U.S. seller with an advertised bore of 12.7mm for $20.44, delivered, and that's what I'm using. I thought I might have to experiment with bigger and smaller bores, but the one I bought seems fine.

By the way, I'm using Finish Line brand Mineral Oil Brake Fluid (intended for bicycle hydraulic brakes). Seems to work fine, and about a thousand times more pleasant to work with than nasty DOT3 fluid.
 
Just thinking… for mounting the slave cylinder, one the mounting holes are located, the inside of the case could be built up with weld, then redrilled and helicoiled, that should make the mount quite solid.
Yes, I am using helicoils, a tip I got from Forum member ippytattoo.
Building up with weld, in addition, is a good idea too, but I don't think it's neccessary.
Two of my mounting holes went partially into back-side webs (just happened, not done on purpose), and I think those two holes are quite strong. The third hole is a bit thin, but I think that with the helicoil it's fine.
 
Some good points and some good questions there. Whenever I finish the video, a lot will be answered. Making a decent vid takes a lot of time and editing.
I'll answer one at a time.
I'm not smart enough to figure out if the rod has to be shortened or lengthened as the plates wear. Two points -- first, the plates take forever to wear. Would probably be ten thousand miles before anything had to be done.
Second.

View attachment 216807
(Incorrect slave shown for illustration purposes only.)
If you make the rod too short, you can just drop a round, washer-like shim in the bottom of the piston rod hole. I'm thinking this is the way to go -- make the rod too short on purpose, then drop three 0.2mm thick shims in the bottom of the hole. Remove or add shims to taste.
The system should take up the 'slack' created by plate wear the same way a hydraulic brake does when the pads wear.

You may need to add a bit more fluid as the slave cylinder has to move toward centerline to compensate, but it should be self-correcting in terms of spacing.
 
Cool read this is..I too have gone down the hydro route albeit with a trials/ktm cylinder but have yet to finish it to see how it performs...out of curiosity, how much travel does your piston need/have to work well??
 

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The system should take up the 'slack' created by plate wear the same way a hydraulic brake does when the pads wear.

You may need to add a bit more fluid as the slave cylinder has to move toward centerline to compensate, but it should be self-correcting in terms of spacing.
Since rod travel distance is a function of master / slave cylinder specs and there is no adjustment, one would need to be careful the clutch assembly isn’t pushed into the right side case.
 
Cool read this is..I too have gone down the hydro route albeit with a trials/ktm cylinder but have yet to finish it to see how it performs...out of curiosity, how much travel does your piston need/have to work well??
I don't know. In at least one of the other threads that I researched, someone got into calculating optimal slave piston travel. But, I figured that Chinese master cylinders are so cheap, that I'd just experiment with different ones until I found one that moved the slave the right amount. My research indicated that a 13mm M/C bore was popular with an Aprilia slave. I bought a M/C with an advertised bore of 12.7mm and it's working fine, no need for further trial and error.

I figure the stroke of all master cylinders is going to be about the same. What matters is the bore of the M/C, and the bore of the slave cylinder. I never thought to measure the bore of the Aprilia slave, but I will the next time I have it off, which shouldn't be too long from now -- I'm waiting for some shim washers I ordered for push rod length adjusting, and then I'll finalize my push rod. My push rod length is fine as I have it now, I just want to make it a bit more "finished."

Your KTM looks similar in over-all size to my Aprilia, but a couple millimeter difference in the bore will cause a significant difference in travel.
 
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I finally finished my installation video, which I also inserted into the very first post in this thread.
The video is a bit long, but there's a lot to it. I hope it's not too choppy and isn't too boring. I now have a lot more respect for video creators.
 
It's a pretty easy conversion -- there really isn't much to it.

Making the video -- that's where the real work is. Not to whine, but making an EDITED video -- as opposed to a "single shot" video -- is a lot of work. Very time-consuming, and a huge software learning curve.
 
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