Need Hydraulic Help/Experts

[Chokse]

OK, here's a question for anyone with a little knowledge of motorcycle hydraulic systems.  I'm working on a project to add a hydraulic clutch to my Magna (no details yet because it is only a working theory at this time). 

The hydraulic clutch (the part on the engine) I am looking to use originally had a clutch master cylinder (the part on the handlebar) with a 14.000 - 14.043 inner diameter piston (I.D)., and a 13.957 - 13.984 outer diameter piston (O.D.).  I cannot use this particular master cylinder because it is from a sport bike and will only work with a 7/8" handlebar.  Also, it does not even come close to matching the look and design of the Magna's brake master cylinder, and I would prefer that it did.

So, here's what I have found after a lot of exhaustive research:

I have only been able to find two clutch master cylinders that look similar to the design of the Magna's brake master cylinder AND fit 1" handlebars (It is important to me that it looks good on the bike).  The problem is that neither has the same size piston I.D. and O.D. as the original master cylinder for the hydraulic clutch I am looking to use.  Here's the size breakdown:

One clutch master cylinder, from a VTX 1800C, matches the look of the Magna's brake master cylinder very well.  I'm quite happy about that.  However, it has a much smaller clutch I.D. (12.700 - 12.743) and O.D. (12.657 - 12.684).

The other clutch master cylinder is from a 1996 - 2003 Honda Valkyrie.  I only have the shop manual for the 1996 Valkyrie, but the master cylinder rebuild kit from Honda seems to be the same part number for all years.  I have not seen a clear picture of a Valk clutch master cylinder, but I think it is a fairly close match to the Magna's brake master cylinder (but maybe not quite as similar as the VTX's).  At any rate, according to the shop manual, the Valk's clutch master cylinder has a larger I.D. (15.870 - 15.913) and O.D. (15.827 - 15.854).

So, here is my dilemma.  Should I go with the smaller VTX one or the larger Valkyrie one?  With the VTX one I worry that it will not create enough hydraulic power to actually activate the clutch (14.000 down to 12.700 is a pretty big drop in piston size).  On the other hand, if I use the Valk's clutch master cylinder, I am worried that the larger size piston will create to much hydraulic pressure and blow out a seal. 

Does anyone have any educated opinions or experience with hydraulics.  I'd really appreciate any useful opinions or information you might have.

If I can get it to work, I do a write up here on the process and what's involved.

Thanks in advance.

[lragan]

The principles behind hydraulics are quite simple.  The thing to remember is that the pressure, in lbs/sq in. or kg/sq cm, or whatever consistent units you like, is the same at each end (well almost the same -- for our purposes, we are going to ignore losses in the tube that connects the two).

Maybe I missed it, but I didn't see the size of the slave cylinder.  It is important, too.  If you want to have the same clutch "feel" that you have with the cable, and if the slave cylinder will actuate the clutch throwout lever at the same place the cable does now, then you must have the same diameter master as you have slave.  Now, you can trade motion for force, so if you want to move the handle on the master cylinder less distance, (and necessarily require more force to do so), you can use a master cylinder with a larger diameter than your slave cylinder.  Conversely, if you want to use less force, but travel a longer distance to disengage the clutch, the diameter of the master cylinder can be made smaller than the slave cylinder.

As for blowing out seals, if you make sure that the total pumped volume from the master cylinder is less than the volume of the slave, you should not have a problem.  So the travel and the diameter come into play in this calculation.  Ideally, they will be pretty close to matched.  If the master cylinder volume is substantially less than the slave cylinder volume, you will not be able to get full travel on the slave. 

I can squeeze with my full grip strength on Maggie's front brake, and not blow a seal.  Of course, I don't have the grip that many of you do, or that I once did, but the point is, you will not blow out seals on a properly balanced system.

Hope this helps.

[Chokse]

Lawrence:

Thanks for the quick reply.  The clutch part I am looking to use (not the master cylinder but the part on the engine that the hydraulic line connects to) is from a VFR 750F.  The shop manual does not give a great deal of information, but I did find this (in addition to what I already posted):


Clutch Slave Cylinder I.D.:   35.700 - 35.762
Clutch Slave Cylinder Piston O.D.:   35.650 - 35.675
Clutch Outer Guide I.D.:   24.995 - 25.012

Does any of this help give you a better idea about the two master cylinders I am looking at and whether or not either one will work?  I suck big time at the math stuff (not the good half of my brain) so me doing calculations is probably a really really bad idea.  Can you tell from these numbers if I can get this to work?  Thanks so much.

[lragan]

Chokse, it appears from the numbers you quote that the slave cylinder will travel only about 15.84/35.66 = 0.444 as much as the master cylinder does, assuming you use the largest master cylinder in your list.  Put another way, in order to get the same travel that you have now with a cable, the clutch handle will have to move 1/0.444 = 2.25 times as far, assuming the same leverage to the master cylinder piston as now exists to the cable.

I have not looked at the leverage at either end of the system you are contemplating.  Probably the master cylinder/handle combination is set up to provide the travel you need, but that is another important factor to consider.  How the slave cylinder connects to the throw-out arm is another consideration.

In order to tell just how each different option would work, we would have to understand how the travel of the handle relates to the movement of the master cylinder piston, and how the movement of the slave cylinder piston relates to the movement of the clutch.

The problem could be simplified by the specifications.  If we knew the volume of fluid moved for the complete travel of the handle (for the master) and the volume needed to move through the friction zone of the clutch (for the slave), we could tell if the two were a good match.  Do the specs say anything about these factors? 

[Chokse]

I can't seem to find anything in the manuals that gives this sort of information, but I might be looking in the wrong place.  I have posted the three manuals in a ZIP file that you can download with the link below.  Sorry, but it is 90MB, but I think it will download fairly quickly.

I am wanting to use the clutch from a 94-97 VFR 750F so I have included that shop manual.  I am looking at clutch master cylinders from an 1800 VTX (all models of all years use the same master cylinder) or a 96 - 2003 Valkyrie (again, all models from each year seem to use the same clutch master cylinder).  I have also included the shop manuals for both of these bikes in the ZIP file, but, and it's a big but.... the Valk manual is in German (the only one I could find to download).  I used a web based translation program to translate some of the terms.  Here's the link and if you find anything that will help you get a better idea about all of this, please let me know.  Thanks for all the help so far Lawrence.

http://dl.getdropbox.com/u/265131/Service%20Manuals.zip

[lragan]

I will look at this, because it is interesting, but it will be a while before I can get to it.

The economy must be improving, because I now have two clients.  I went from November of last year until July this year with no work at all. 

I am grateful for the work, for sure -- but I do have to get it done!!

[lragan]

Chokse, I have looked at these manuals, and I cannot sort it out. 

If you have the opportunity to do it, this is what I would try to do:

1) Measure the total travel on the clutch throw-out arm on your Magna as you operate the clutch lever on the handlebar through the entire travel.  (this presumes the slave cylinder will be attached at the same point as the cable is now.  If it isn't, measure the travel wherever you plan to attach it.

2) Find a physical motorcycle of the type you are planning to copy the hydraulics from.

3) Measure the travel of the throw out arm (If possible) on this (these?) bikes as you move the clutch lever through its entire range.

If you find one whose travel matches what you measured in 1), use both the master and slave cylinder from that model.

Or if you like a particular master cylinder, go measure that bike first.  If the travel is not right, try to adjust the travel by picking another slave cylinder.  The travel is inversely proportional to the square of the diameter, so if you need to increase the travel to fit the Magna, use a smaller diameter slave cylinder. 

The math goes as follows:  diameter1/diameter2 = sqrt(travel2/travel1).  ( "Sqrt" is abbreviation for "square root".)

You would need to look at the slave diameter specs and get as close to the right ratio as possible.  My guess is that the clutch systems are not all that different, and a matched set from a particular model bike will work -- but that is just a wild guess. 

Is this helpful?  I hope so.  Sorry I couldn't figure it out from the manuals.  Let me know what you learn.  I am certain others are interested in this conversion...

[Chokse]

Lawrence:

I have done a little of my own research over the past couple of days and here is what I found.  The VFR, VTX, and GL 1500 all use the same clutch piston (the part on the engine).  I checked part numbers and all three are the same!  If they all use the same clutch piston, then any of the three master cylinders should work fine.  Right?  From what I understand, you've got a piston at the master cylinder and a piston near the engine with a hydraulic hose connecting the two.  If all three of these bikes use the same clutch cylinder, then any of the three master cylinders should work perfectly fine with it.  If that's the case, I think I'll go with the VTX because it is cheaper, and it is a perfect match for the brake master cylinder.

Based on this information, what do you think?

[Charles S Otwell]

I've been following your discussion, and I'm not sure I understand, you are talking about replacing the clutch cable on a third gen Magna with hydraulic type like used on the earlier models? If so where and how will you mount the slave cylinder to the engine? Also just out of curiosity what would be the advantage?

[Chokse]

Charles:  No, that's not what I am doing.  I am doing the VFR engine swap and while I am at it, I want to upgrade to a hydraulic clutch by utilizing the VFR's sprocket cover.  In the following link, it is item #1 (and several of the other smaller items shown in the fiche picture).

http://fiche.ronayers.com/Index.cfm/Module/Main/TypeID/26/Type/Motorcycle/MakeID/1/Make/Honda/YearID/37/Year/1996/ModelID/7481/Model/VFR750F/GroupID/328595/Group/WATER_PUMP

If you look at the Magna's parts fiche, I would be replacing the cover found under "Water Pump".

If you look at the picture in the link above (for a 1996 VFR 750), you will see the hydraulic clutch piston (not to be confused with the clutch master cylinder piston) which is item #12.  You can also see where the hydraulic hose connects (item #10).  The hydraulic clutch piston (item #12) is the same part number (22863-MJ8-003) as the one used on the VTX 1800 and GL 1500.  This is why I think either clutch master cylinder (VTX or GL 1500) will work.

I want to convert to a hydraulic clutch for a few reasons.  First, I am pretty lazy about lubricating cables, and have twice had the clutch cable snap at very inopportune times.  Aside from the fact that a new cable isn't cheap, both times it has left me stranded on the side of the road.  A hydraulic clutch would eliminate this.  How many times have you had your brake hose burst?  Also, a hydraulic clutch is easier to engage (takes less hand strength).  I'm more than strong enough to engage the cable clutch, but I live in city of 20 million and most of them have cars.  The traffic jams get pretty serious and I am stuck in stop-and-go traffic very, very often.  When you are in a heavy traffic jam for over an hour, constantly working the clutch lever, your hand starts to get pretty tired.  While a hydraulic clutch would not eliminate this entirely, it would make things much easier for me going to and coming from work each day.  Finally, I want to do it because I think I can, and I always like doing something that most other people have not done. 

It's like when George Mallory was asked in 1924 why he would possibly want to try to climb Mt. Everest, he replied, "Because it's there."  I kind of feel the same way.  My bike is apart right now (completely apart) and I am in the process of doing a number of mods.  I am adding wheels that will work with radial tires, dual disk brakes on the front and a single disk brake on the rear, swapping out the innards of the VFR engine for the innards of the Magna engine.  While I'm at it, why not add a hydraulic clutch?  In doing the VFR engine swap, I had to make a new wire harness to get everything to work (basically a Frankenstein harness made from Magna and VFR harness parts).  I went ahead and added in the VFR's clutch diode wires, fuel sending unit wires, and electronic speedometer sending unit wires.  This way, if I ever decide to add something like a Dakota Digital speedo/tach, I can get rid of the speedo cable and move to an electronic system, and if I add a fuel sending unit to the Magna's tank, I can have the speedo/tach gauge show my fuel level as well.  Some people will think it's a waste of time and money, but it's my hobby and it keeps me happy.

[roboto65]

Some people will think it's a waste of time and money, but it's my hobby and it keeps me happy

And thats all that matters is it not !!!! But the Hydraulic may not make it as easy as you think my Valk is just as hard as the Magna if not worse and it is Hydraulic I think the reason for the maker going Hyd is because of the increased Clutch spring pressures on say the Valk and the Sport bikes.  Just a theory 

[Chokse]

Your theory is probably correct, but I'll be using the Magna's clutch springs, so it should be no worse than the cable.  It will also prevent me from dealing with snapped clutch cables and will require less maintenance.

[Charles S Otwell]

Finally, I want to do it because I think I can, and I always like doing something that most other people have not done. 

Well now that, I UNDERSTAND!! 

I'm working on a project to add a hydraulic clutch to my Magna

Sorry, I saw Magna and missed the part about the VFR swap .. Now it makes more sense, not that I ever doubted that you could do it to the third gen engine  But for the life of me I couldn't figure how ..  Can't wait to see the finished product, good luck..

[lragan]

Lawrence:

I have done a little of my own research over the past couple of days and here is what I found.  The VFR, VTX, and GL 1500 all use the same clutch piston (the part on the engine).  I checked part numbers and all three are the same!  If they all use the same clutch piston, then any of the three master cylinders should work fine.  Right?  From what I understand, you've got a piston at the master cylinder and a piston near the engine with a hydraulic hose connecting the two.  If all three of these bikes use the same clutch cylinder, then any of the three master cylinders should work perfectly fine with it.  If that's the case, I think I'll go with the VTX because it is cheaper, and it is a perfect match for the brake master cylinder.

Based on this information, what do you think?

I agree that either will "probably" work. If you use the one you like, as opposed to the one designed to work with the slave you have, your master cylinder travel will have to increase, but not by much (14.02/12.72)^2 = 1.21, or 20% further.  If the leverage is the same on both master assemblies, you will have to move the clutch handle 20% further to operate the clutch.  You will have, in effect, a little more leverage on the clutch spring with this arrangement.  I don't know if the master assembly leverage is the same or not -- could not tell from the manual.  What this boils down to is whether the distance between the pivot and the piston is the same in both assemblies.  You can probably tell by looking at them closely if you have that chance.

I hope you are taking lots of pictures of this modification process.  I think a lot of us will be interested in both the process and the outcome.  Good luck to you on this project.

[Chokse]

Lawrence:

That's what I think I'm going to do.  I checked into the VTX 1800 master cylinder and two are listed with very different prices (one is about $50 higher than the other, but both use the same piston set).  The guy at Ron Ayers was as confused by this as I was, so he is going to order both and find out what the difference is (probably one is painted and one is brushed aluminum).  At any rate, I will end up getting one of these two VTX master cylinders.  If lever travel becomes an issue, I can always pick up a pair of Pazzo adjustable levers from Ebay.  Expensive, but it would correct any lever related issues. 

Thanks for all the help and I am taking lots of pictures.  Once everything is done and I have a little time to ride (haven't ridden my bike since March!!!!), I'll post the pics on my website.