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Hydraulic Clutch AKA Broken Cable Blues

Jays100

Veteran Member
Joined
May 29, 2020
Total Posts
720
Total likes
227
Location
Enfield, CT USA
More than once, I’ve had broken clutch cables which have left me stranded, or forced me to resort to extreme measures to get home. The last time was a few months ago in heavy traffic. Fortunately I had a spare at home so a repair was easily and quickly accomplished. But I had to push to get moving, jam in gear and shift at easy throttle. Push, jam, repeat, all the way home.

Fast forward to a project bike and clipons don’t lend themselves to cable operations without interferences and length issues. Plus, no symmetry from either side of the bike.

To fix, I’ve adapted ideas from all over and the result is a hydraulic actuator, the right length hose made to order for small money, quality handlebar master cylinders are a matched set side to side (and on sale too, bonus!). The catch is no slave cylinder exists, well, until now.

22EB5D79-8AA6-4C0E-80D8-19DC0D92809A.jpg

I’m still operating from hand sketches and pencil calcs but the design is there and discounting my labor, for about the same $$ as a replacement cable. Er, not counting handlebar cylinders, and new switch gear, and throttle pipe, and throttle cable. Okay, okay, so it’s not cheaper but it did achieve my goal of cleaning up the handlebars.

Eventually, I’ll post the various costs and how well they work.
 
I like the idea and did consider the possibility for my drag bike project, but for it the cable and factory actuator is simpler and might also be lighter in the end. But that was also using an available slave cylinder modified to fit, and your idea looks smaller and lighter.

So in theory I could (eventually) have a bike with a Jays100 high output oil pump, an EI with electronic advance and ridiculous spark energy AND a hydraulic clutch. Cool.
 
…sponsored by Miles Beyond Ordinary Designs….lol

Would there be a market if it were a kit? More to the point, is the cam actuator the same for all of the models? 175/350/450?
Such a kit would include the clutch master, slave and a hose. Also requires switch change so how far would it go?
 
I just ordered the piston seal and internal preload spring. It’ll be working (or not) by Christmas.
 
…sponsored by Miles Beyond Ordinary Designs….lol

Would there be a market if it were a kit? More to the point, is the cam actuator the same for all of the models? 175/350/450?
Such a kit would include the clutch master, slave and a hose. Also requires switch change so how far would it go?

The actuator is similar on those 3 models, except the 350 uses that little 3 ball part but the basic operation is the same. The 175's version is in the left crankcase cover while the other two are in the front sprocket cover. I don't think there would be as much interest in it as there would (should) be in the gear oil pump, but I think you'd find some of our members interested. And for those who have the integrated left switch with clutch lever perch in it... yeah, it would cost more money to go with a later separate switch and perch. My red 450 uses a plain perch on the left because I'm using the starter button for the horn, so in my case it wouldn't matter.
 
YES ! This is great of you Jays100 :) I really miss hydraulic clutch actuation,especially when sitting in 'stupid traffic';I used to own a First Generation 1986' Honda VFR750F1 and it spoiled me.
 
Have to figure out some kind of scale to measure the difference in lever force but if it’s easy enough, shouldn’t matter. I guess if my wife can squeeze/hold, will be good for anyone!
 
@Richard
Normally I would agree, this is a unique case.
Preventive maintenance is an elusive thing for stuff outside of oil changes and the like. I had lubed this cable so it was in good shape at the beginning of the year. Where it broke was at the handlebar barrel end. There was no fraying as a precursor of impending fail, it was a clean break, all strands went together. Clearly the molded barrel end wasn’t moving properly inside of the lever pivot and flexed into a fatigue fracture. Admittedly that is a maintenance grease point, grease had washed out. However, this one I’m chalking up to component quality, not maintenance. The new, cannibalized, cable is like silk!

The spare cable was from another bike. Now, that bike is being assembled but with clip-on handlebars and the clutch arrangement interferes with the headlight ears. A different solution was needed hence the hydraulics idea. That allows me to route in uniquely and keep the chrome headlight ears intact. The clutch actuator area is a big spot where nothing much is happening and a rear set shift linkage opens it up more. In my opine, just makes the engine even more interesting.
 
Edit wonky this morning. I meant @ 450roo

@Richard, yes on the VFR, Gold Wings, Suzuki uses…all are too large diameter to fit the cover. I used a master cylinder from a KTM and made a slave to fit the cover.
 
That’s the same failure mode that left me stranded before. Admittedly I’ve gotten better about re-lubing it, but if there’s an upgrade available that would have me A) not worrying about it ever again, and B) giving me a less fatiguing solution for city traffic, I’m all for it.


- 1972 CL350
- 1985 VF700F
 
Some photos of my vision/progress.
How it fits in the cover
Clutch - 1.jpg

Side view
Clutch - 3.jpg

Clutch master view, shows hose clearance
Clutch - 4.jpg

Wide view
Clutch - 7.jpg

Dash view, shows symmetry of controls and clip-on handlebars. Yes I know the fork tube height is not set. I have a USB/voltmeter next to the key switch.
Clutch - 5.jpg

Front
Clutch - 6.jpg

Wide side, the stock CB gas tank will be used, it's a good size/shape for this build. Much to be done.
Clutch - 9.jpg Clutch - 8.jpg
 
Great work thus far, Jay! Really impressive. How will clutch adjustment be done with the hydraulic lifter?

Side notes: I guess you have a cafe racer in the works? Does that tank in the background belong to this build?
 
If you're wondering, I tend to use my builds as test beds for my ideas and so don't start a build project. There are some big gaps in my progress photo's is another reason.

Here are my costs for the Hydraulic changeover:

36 Master Cylinders (both clutch and brake)
75 Clutch actuator (est retail)
12 Hose, clutch
33 Switches (both sides)
00. Contribution to my delinquency
37 Clip-on handlebars

205 Sub total for this part of the project
 
Yes, Cafe style.
Apologies for the parallax error from my phone camera, makes the seat look way bigger than the tank but isn't the case.
Clutch - 1 (2).jpg
 
The interesting thing about hydraulic clutch actuation is an internal spring keeps the piston/plunger pushed against the actuation rod. Therefore, no matter what direction the clutch wears, the piston and thus the handlebar lever engagement point is always the same.

An automatic adjustment if you will.
 
Barrel end lube at the lever (or lack of) did him in
It still means he had to pull the cable too hard, which is why I think it's binding somewhere.
My 450 and Valkyrie both have about the same pull force, so hydraulics, in and of themselves, don't make it easier.
 
Right, not necessarily easier, we’ll see.

My purpose was to clean up the controls. But to your point, it’s a $$$ solution to a $$ problem.

The routing was fine, it was the first thing I checked. Because the break was exactly at the barrel, it was not routing. The barrel simply didn’t rotate to keep the cable pull straight, but bent repeatedly at the cast joint, and broke.
 
The old solution to a broken clutch cable is to remove the outer cable and tie off the end of the inner somewhere convenient where you can get hold of the inner cable and pull that for clutch action. I have done this several times, at times for long rides home.
Just in case someone has not heard of this method.
 
Well, todays myth is it will be a permanent solution for this bike.

Regarding problems, my Ducati needed a fluid change yearly to work properly. The seal was changed every 2 years. No worse than cable maintenance and adjustment, just different.

I do get carried away though. ??????*♂️
 
Question to the forum, What is the clutch spring rate? I'm not finding anywhere, does anyone know?
Conversely, what is the load at installed height? Either will do.

Here are my calcs, a man's squeeze is 35# which translates to 577# at the clutch to disengage with a .353" (8.9mm) stroke.
 
Question to the forum, What is the clutch spring rate? I'm not finding anywhere, does anyone know?
Conversely, what is the load at installed height? Either will do.

Seriously? :lol: (speaking for myself only, of course)

OTOH, can't you just use a master with either a smaller (or larger, hell I don't know) piston if you need it to be an easier pull?
 
The original 6-spring clutch used springs rated at a free length of 40.1 mm, and 26.6 mm with a load of 31.6-34.1 kg. I'm guessing you can derive the rate from that.
 
@ WintrSol, you rock!
@ ancientdad, I'm considering the possibilities from all angles, which present many scenarios of problems. For instance, if too long travel, will the pressure plate rub on the outer cover? Or if the stroke is reduced (via volume displaced/larger diameter) Where does that diameter come from and how do I bleed air? But I do have a working system right now. If it works, well, it works.

I'll solve all of those problems but the more I can identify and solve on paper, the better it will be. You want that, right?
 
KTM MX and Enduro bikes around 2010 use a small hydraulic 'pull cylinder' that could probably be adapted.
I've been thinking of doing a hydraulic conversion to a 360 for several years, bore the original housing and fit a piston in there. (the easy bit) running a line that fits into original location and doesn't look out of place is the issue. The external line you have isn't exactly looking good in my opinion
It would be easy if I could weld alloy as a block could be welded in then drilled and tapped for banjo bolt.
The other thing that made me 'put it on hold' is the chance of fluid boiling when sitting in traffic.
It's an issue on several bikes with hydraulic clutch operation but they are mostly cruisers or haven't had fluid changed in years.
 
Isn't DOT 5 fluid supposed to help avoid the boiling issue? When I worked for the City of Tampa garage we changed all the old Kelsey-Hayes master cylinders on the Harleys to DOT 5 fluid because they had boiling problems (though we never actually experienced it ourselves when we test rode them, though the cops ran long funeral or oversize load escorts with long wait times at intersections might have). If true, it seems like that would work with a clutch slave
 
Yeah, boiling out the fluid is definitely an issue and has happened to me. I ended up using a Motul product and changed that every year which stopped the problem. I have also seen non-failed clutches with coffee colored fluid so one never knows on these things.

@CrazyPJ by original location, are you wanting the hose to route in the same oblong opening in the side cover and down to the slave? Trying to understand what you meant. The pull cylinders work with the same cam Honda uses (or gear rack in KTM's design).

In this case, my thoughts revolve around chemical compatibility. Glycol based brake fluid systems typically use seals of EPDM rubber, but, fluids like chain lube, need a butyl, or neoprene rubber for compatibility. Typical hose is resistant to brake fluid but not chain lube. More research is certainly needed. Anyway, having my hose run outside of the cover solves this nicely by virtue of a physical barrier between chemical stressors. Of note is temperature is a consideration but not an issue. It becomes an issue when rubber is borderline compatible where a heated fluid will accelerate chemical breakdown or swelling. We wouldn't use that material.

Another possibility is to weld/braze a tube to reach from the slave cylinder up to the top of the crankcase and attach a hose there, a very good solution if we could do it in a cost effective manner.
 
I have no experience with the Dot5 systems. Do they take special seals? *sigh* more research...
 
I have no experience with the Dot5 systems. Do they take special seals? *sigh* more research...

All we had to do back then (1976-77) was fully flush the DOT 3 fluid out with DOT 5, then bleed it and done. No seals had to be changed.
 
Okay, I think Dot 5 can and will be a superior fluid but it is $$, not $. Its usable range high is 350F/180C +.
As Dot 3, 4, 5.1 are all glycol based, they're hygroscopic (have an affinity for water) so their boiling points are generally lower. It's interesting that 5.0, silicone based, has an affinity for air so sloooooow bleeding is critical.

And, to convert from glycol to silicone fluid, denatured alcohol (itself hygroscopic to some extent) is used to clean/purge the old fluid from the lines - ancientdad notes this clearly from first-hand experience. no other changes needed, liking this immensely.

I think the problems of fluid boiling etc. in a hydraulic clutch system used on an air-cooled motor would be well served to use a Dot 5.0 fluid (and not 5.1) to begin with. It will certainly age better with no water in the system.

Applying the same logic to the front brakes, then, with no water present, the corroded and stuck disc brake calipers may experience extended life in a rebuild and subsequent storage environment. Further, the silicone based fluid is non-caustic to painted surfaces.

Love these discussions!
 
The nice thing about dot 5 fluid is that it won't eat the finish when it gets spilled on painted parts, unlike the other fluids.
 
Whatever you use there will be issues.
Silicon based fluids have long term problems that most people are not aware of.
US Military switched all vehicles to silicon base so there wouldn't be a problem changing fluid every 1>3 years.
What they found was, condensation could still get into the system but at a slower rate, water droplets would accumulate at the lowest point and destroy whatever they were in contact with.
DOT 5, has a shorter lifespan than DOT 3 as it's 'more' hygroscopic and should only be sold/stored in metal containers.
Yes, I want to run line into same position as original cable, never thought of a smaller diameter tube to connect above cover, it would look like original cable adjuster.
Thanks for the idea
 
Isn't DOT 5 fluid supposed to help avoid the boiling issue? When I worked for the City of Tampa garage we changed all the old Kelsey-Hayes master cylinders on the Harleys to DOT 5 fluid because they had boiling problems (though we never actually experienced it ourselves when we test rode them, though the cops ran long funeral or oversize load escorts with long wait times at intersections might have). If true, it seems like that would work with a clutch slave

Dot 4 brake fluid is good until 446 degrees F. which is a plus.
 
Looking at fluid properties can be confusing. Brake fluids have wet and dry boiling points and in a practical sense, only the wet numbers should be used, those are real world limits. The dry boiling point would be used for lab work, or perhaps in a racing environment where the fluid is refreshed frequently.

Regarding water pooling into low points of a system, as Dot5 fluids are anhygroscopic (anti-water absorption) and their specific gravity is <1 (its lighter than water at .953), then, any moisture that exists in the system will eventually percolate down via gravity, to the lowest point as the Dot 5 fluid will float on the water - (remember, the mix is not in solution). To be clear, unless the system is open, we're only talking less than a drop of water, negligible by all accounts and if seals have even a modicum of integrity, will vigorously resist water ingestion.

Regarding ideas, please post a pic of what you end up with!
 
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I only found out about military use probably 2003 or 04.
They had vehicles stored for years but didn't specify how long.
I used DOT 5 in 1980's and it had been out for a long time even then so could have been 10 to 20 year long term storage?
In that much time water molecules will pass through the rubber (which also deteriorates)
 
My Calcs

Here is a snap of my calcs to arrive at relative sizes and loads. There has been an interest expressed to approach this differently so this should help.

Note that your master cylinder choice determines the slave cylinder dimensions and is influenced by load and stroke desired.
 
Calculations sheet

hon 450 hyd clutch act.jpg

In short, the master cylinder I chose will result in a lever pull force of 19 lbs/9 kg. Typical adult strength is 35 lbs/19 kg and a .23"/5.8mm stroke. There is a window to go up one more o-ring size to bring both the lever force exerted and stroke result and remain within the dimensional limits of the cover.

If a clutch master cylinder is harvested from a VFR for instance, a redo of the calculations is required to keep both stroke and force within appropriate boundaries.

Feel free to post your approach or PM if further engineering is needed.
 

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Useless trivia

It is also interesting to note that similar calculations are used for hydraulic braking systems. To complete, further calcs are needed for the various frictions and leverages. Not real complex but definitely very involved. That is, brake pad to disc friction, disc size lever, wheel size lever and rubber-to-asphalt friction (wet surface used) are needed.

Disc type brakes were first patented in 1902 by Frederick Lancaster, Birmingham England.

It's unclear when the first hydraulically actuated clutch mechanism was first used in the automotive world.
 
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