"Bolt-On" hydraulic clutch conversion

[mrriggs]

I've been wanting to do a hydraulic clutch conversion for a long time but a hand injury this year has made it a priority. I decided to make a "bolt-on" slave cylinder because it was an interesting challenge. It is a direct replacement for the stock clutch actuator, with no modification to the side cover, and it uses the stock pushrod.

I made the body of the slave cylinder from cast iron and the piston is stainless steel. It mounts to the side cover with a snap ring. A stud is screwed into the lower screw hole that fits into a hole in the backside of the slave to prevent it from turning.









I made a hard line that runs up through the cable hole and meets the soft line under the tank. It was covered with heat shrink tubing to give it the appearance of a cable.



Bleeding the system does require removing the side cover which isn't that big of a deal considering how often you need to bleed a clutch. I used the reverse bleeding method which was quick and effective. Hook a big syringe of fluid to the bleeder and push it through while sucking the excess out of the master reservoir with a second syringe. Then push it in and out a few times to be sure all the air is out. Close the bleeder and you are done.

I despise brake fluid so this was designed as a "mineral oil" system. You will hear all kinds of opinions on what fluid is best; baby oil, ATF, fork oil, power steering fluid, or even [gasp] mineral oil brake fluid. I like fork oil because it's easy to get, has good lubricating properties and seal conditioners. I'm using the thinnest stuff I could find, RedLine "Like Water".



I'm using a 9.5mm Magura master cylinder to get the lightest pull possible. The only thing missing is the mirror mount, although that is an option with this master.



A picture of it all buttoned up. Notice the little chrome cover still fits on there to cover up the snap ring.



To say that this thing has a light pull is an understatement. It feels like it's not even hooked up. The best part about it is the feel, it is so smooth and there is no hysteresis. It engages and disengages at the same spot, and with the adjustable lever you can pick exactly where that spot is. I absolutely love this clutch setup, it has transformed the feel of the entire bike. The only question that remains is how well it will hold up with daily use.

[preston]

MrRiggs :
this is great set up you have developed, and your photos are great to help understand..... Maybe you could market this ?
Impressive.
I use bar-end weights with end /bar mirrors, which work well for me.
Preston

[grizld1]

Elegant work--thanks for sharing!

[10ecjed]

I like it.

[rockhead]

as with many good ideas ..... click on the link. a very neat hydraulic clutch

www.heidentuning.com/p/28/3609/mo74-cgp1%7C22=2/%23ht-6599-hydraulic-clutch-kit-now-special-price%21

[grizld1]

With the banjo fitting and line hanging out in the breeze, I wouldn't call Heiden's product "neat." It's ugly, exposed to damage, and overpriced. I'll give Jerry Heiden this much, though; he's a true artist when it comes to getting a dynamometer to produce the numbers he wants to see.

[mrriggs]

It's funny that you would call the Heiden setup overpriced, I was just about to comment about how cheap it is. Mine cost twice that much and that doesn't even count the labor.

[grizld1]

Brett, I commend your modesty, but there's no comparison--an old Ford Escort is overpriced at $10,000, and that fact doesn't change because you see a good Mini Cooper that costs more than twice that much. Your design and components are far superior. IMO the Heiden kit is overpriced for what it is.

[mrriggs]

I've noticed that most aftermarket parts aren't made to last. But then, most of these old bikes aren't ridden enough for that to really matter. Say you have a $500 part that will last 50,000 miles and a $250 part that will last 5,000 miles. Simple arithmetic says that the more expensive part is the better value, but if a guy only ever puts 2,000 miles on his bike then it doesn't really matter. The cheaper part is "good enough" and he'll have an extra $250 for "hard-core" stuff, like glitter paint.

[mrriggs]

Just a quick update. It was 21°F this morning and the clutch pull was just as light as ever. The stock clutch would stiffen up quite a bit when cold.

Also, my weepy old push rod seal no longer leaks because there is no up and down movement from the slave cylinder. It had been leaking badly for several months. I put off replacing the seal and bushing because I wanted to see how much the new slave would help.

[flea]

very nice,please say you will market it (would put my stuffed hand up),but as far as heidens go your right, by the time you add the master cyd,oil line to be made up ( we cant all do it our selfs) and slave its still not to bad a price but if had a choice would definitely go your version.like the more hidden look of it

[mrriggs]

I never planned to market it but there is a guy who has expressed interest in buying the slave cylinders from me to assemble a kit. It's all rather premature now. I want to put a lot more miles on this before I would ever consider it.

[b.]

You mentioned you used a 9.5mm MC. What was the size of your slave cylinder? I heard a range of requirement for pressure plate movement, from 2-3mm, 4mm, 5mm. No idea whats really needed. At your spec's to get just 2mm of movement you would need to have a 25mm or smaller slave cylinder.

Thanks.

[mrriggs]

My slave cylinder is a 1" (25.4mm) bore. Bore ratio is only half of the equation. You also need to account for the lever ratio. Magura lists the lever ratio for my master as 4:1 with a max piston travel of 13.8mm. I'm not sure where on the lever they were measuring travel to come up with the 4:1 ratio. When I measured the travel at the ball on the end of the lever it was 105mm at max adjustment and 78mm at minimum adjustment. The respective piston strokes were 13.5mm and 10mm, which is a ratio of 7.8:1.

I haven't pulled the right cover to measure pressure plate movement but it calculates out to 1.4 - 1.9mm depending on the lever adjustment. I have the lever adjustment somewhere in the middle so I'm probably getting about 1.7mm pressure plate movement.

[b.]

Thanks for the input. Presuming lever ratios are typically close to one another. I'm using a Brembo 13mm master with 12mm travel. I did get a chance to rig up a measurement of maximum movement of using the stock pully-screw mechanism and I was consistently at 2.08mm. Mind you that's without any resistance applied. The BMW K1200 slave is 32mm which gives me 1.98mm of travel if I use the entire stroke.