Hydraulic Clutch Actuation for GT380

[markush]

Hydraulic clutch actuation for GT380

With the original clutch plastic release screw, the pressure point changes constantly during operation, so the clutch cable often has to be adjusted while driving, when the engine has warmed up or if the clutch is used frequently. This gets worse if you also have installed reinforced clutch springs.
In addition, the disengagement path on the push rod is often not enough to disengage the clutch sufficiently, so it is often impossible to switch into idle gear when standing and engine running.
With a completely new clutch and a new clutch release screw, the problem is not very pronounced. But most of us are likely to be on the road with parts that are not so completely new.

To get rid of all this, I built a hydraulic clutch actuation. Nothing has to be adjusted here, the pressure point is always the same and the release travel on the clutch push rod is reliably at least 2.5mm, so that stuck switching into idle is a thing of the past.

The slave cylinder has the same external dimensions as the original release screw and can be installed directly in place of it.

before

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after

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dust cover

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The steel flex hydraulic line is routed in the same way as the clutch cable before. For this I made some fittings which sit in place of the clutch cable adjustment screw. In this way, no machining is necessary on the gearbox cover.

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[markush]

The clutch pump comes from the accessories (Far East). It has been slightly modified to use an original GT (brake)lever so both sides levers are the same.

IMG_0008_(640_x_480).jpg

[joolstacho]

Excellent work there mate.
How is the actual slave constructed? Obviously it must have a piston and seal in it, and a return spring?

[Alan H]

I did something similar on a GT550 here - https://www.kettleclinic.co.uk/kcforum/ ... &start=310.
A great improvement and easier on the hand, plus it offends the purists - usually when it's pointed out to them!

[markush]

Excellent work there mate.
How is the actual slave constructed? Obviously it must have a piston and seal in it, and a return spring?

Thank you!

Yes, it's like a disk brake cylinder. No spring necessary, the piston is pushed back by the clutch springs via the clutch push rod.
The piston has a bore for the push rod, with a bearing ball inside and a seal to hold some lubrication in place between push rod and ball.

IMG_0004b_dr.jpg

[jabcb]

A GT380 at the recent Steel City Mods & Rockers has another hydraulic clutch solution. The owner said he used Magura Hymec parts.
https://www.magura.com/en/components/po ... chsystems/

[markush]

I am aware of the commercially available universal solutions shown above and have deliberately not chosen them because they use the original clutch release mechanism. They actually just replace the clutch cable with a hydraulic line. On the GT550 this may give a small advantage. Certainly not on the GT380 with the plastic clutch release screw, because this part mainly causes the problems mentioned above.

Apart from that, I don't like at all this slave cylinder throning on the gearbox cover.

Magura's assertion that with their hydraulics the manual force required on the clutch lever would be significantly less can also not be left uncommented.
You have an approximately constant hand lever travel available, this must be converted into the approx. 1-3mm movement of the clutch push rod. This results in a transmission ratio for the forces that occur. First of all, it doesn't matter how the translation mechanism is designed.
In practice, it can of course be that a hydraulic system runs more easily than a rotten clutch cable.
Apart from reduced friction losses and the like, you shouldn't expect any further clearly noticeable reduction in the pulling force on the clutch lever if you don't change the transmission ratio.

[jabcb]

The owner of that GT380 said that the Mangura hydraulic clutch didn’t make much of a difference.

He build a very nice & usable show bike. With monoshock, 3-into-1 exhaust, a GS front end, GPS speedo/tach & hydraulic clutch. Not sure, but I think it also has CDI ignition. Won second place in the Japanese class at Mods & Rockers.

My Honda Nighthawks have a hydraulic clutch with a slave cylinder much like brake calipers. Works quite nicely.

[Alan H]

Using a larger master cylinder than the slave makes a greater movement on the slave cylinder as I did. It has worked fine for two years now and hasn't needed any adjustment - and the bike gets used regularly, so certainly works for me. It isn't a show bike, it's a practical rider built by me for my use and preference.
Arthritis in my hands makes pulling a clutch in awkward after a time, so the mod I did eases that too. People usually have different ideas of how to do things, it doesn't mean that any are bad, just different.

[markush]

Using a larger master cylinder than the slave makes a greater movement on the slave cylinder as I did.

Yes.

And that increases also the force needed on the hand lever.
If one has problems with the hands (as I also have sometimes), one should use a master cylinder smaller then the slave cylinder.
But this then also decreases the slaves piston- and push rod travel, so one has to find a mid way between lowest possible lever pulling force and minimum needed clutch disengagement.

I assume, when buying such a commercial hydraulic conversion kit, it comes with master and slave cylinder at the same size to maintain the original transmission ratio in the clutch release mechanism.

[markush]

Short field report in keywords after a year has passed since installation.
Driven a couple of tours, no leakage, function still good, stable pressure point, clutch separates perfectly, shifting into neutral while standing with engine running is no problem.
So it has proven itself.

There is a minor change to the lower hydraulic line for easier manufacture and installation:
http://suzuki-gt380.de/gt380_dateien/mo ... 0Kupplung/ (last pics)


What is still annoying are my reinforced clutch springs with the increased manual force required. But currently I can't force myself to "pick apart" the engine for this, I rather drive.

[Alan H]

It's good to be different - and upsets the purists at the same time!