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Stray

Different clutch slave cylinder sizes?

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Hello All, 

 

Does anyone know how the clutch space piston size of our VFRs (and other Hondas) changes over the years? 

 

I know a few numbers:

- 5th gen clutch slave is 35.6mm

- VTR1000 clutch slave is 35.6mm (I’m assuming as same part number)

- 6th gen clutch slave is 33.5mm

Oberon clutch slave is 38mm

 

Not sure if all 6th gens are same across the years? What about 8th gen? What about other Hondas with the same type of slave? CBRs, Blackbirds, Pan Europeans etc? 

 

I’d like to fit a bigger piston slave on my 5th gen but don’t know which one (other than Oberon).

 

As as an aside, if you’d like a softer clutch on your 6th gen you may want to try a 5th gen slave. You’ll get longer lever travel and more modulation. 

 

Best,

 

Stray

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5 hours ago, Stray said:

Hello All, 

 

Does anyone know how the clutch space piston size of our VFRs (and other Hondas) changes over the years? 

 

I know a few numbers:

- 5th gen clutch slave is 35.6mm

- VTR1000 clutch slave is 35.6mm (I’m assuming as same part number)

- 6th gen clutch slave is 33.5mm

Oberon clutch slave is 38mm

 

Not sure if all 6th gens are same across the years? What about 8th gen? What about other Hondas with the same type of slave? CBRs, Blackbirds, Pan Europeans etc? 

 

I’d like to fit a bigger piston slave on my 5th gen but don’t know which one (other than Oberon).

 

As as an aside, if you’d like a softer clutch on your 6th gen you may want to try a 5th gen slave. You’ll get longer lever travel and more modulation. 

 

Best,

 

Stray

I have just fitted the Oberon to my 6G and it is a thing of great wonderfulness, lighter than my CBF 125 and the pick up is over a longer period making moving off and slow riding a much more pleasant experience.

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Didn’t know 5th and 6th were different. I know 5th shares part # with RC51. I put an SP1 master on mine with a braided line and think it is much improved. Probably more the line than the master. 

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13 minutes ago, BuzznerSuntrusts said:

Probably more the line than the master. 

 

The lines on these things are 20 years old. I did my clutch with braided when I did the brake lines and it was a cheap, easy upgrade. It improved consistency as much as anything.


Never thought to swap the slave, though. What sort of difference did you find when you swapped it all out?

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I did the entire front end and had the parts on hand, so that's why I went with the SP1 master. I just felt better. Firmer, I could cycle it faster in multiple gear downshifts/blipping.

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Braided clutch lines are pure bling.  They are under almost no hydraulic stress whatsoever.  Bleeding the system after fitting the new line probably accounted for all of the improvement!

 

I am surprised there are even that many Honda clutch slave cylinders.  Of course, most of my Hondas are from the same two eras, so that might account for my lack of exposure to different ones...

 

Ciao,

 

JZH

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I forgot about my Pan. I picked up a '92 ST1100 earlier this year as a project. Turned out the master cylinder return port was plugged solid so I stuck my old VFR master on it as they are the same. Guessing the slave cylinder is close to if not the same as 5th Gen.

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Buzzner, what behavior does a master cylinder with a plugged return port exhibit? I’ve been chasing a soft-levered 5 gen delinked front brake system for ages, bled the system carefully multiple times, rebuilt master and calipers w OEM Honda parts, but didn’t know about a return port or how to check it.

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On 5/17/2019 at 7:57 AM, Stray said:

...

- 5th gen clutch slave is 35.6mm

- VTR1000 clutch slave is 35.6mm (I’m assuming as same part number)

- 6th gen clutch slave is 33.5mm

Oberon clutch slave is 38mm

 

 

I assume that's the 5th gen Oberon you have listed... drawing some conclusions from their model numbers, the 5th gen - model CLU 3038 - is 38mm while the 6th/8th gen CLU 3036 - is probably 36mm, and is the only 36mm model they offer in their Honda section.

 

Also, has anyone confirmed that the 5th and 6th slaves are a simple swap? I'm thinking in can get most of the benefit of a 36mm Oberon in a used 35.6mm 5th gen slave and a rebuild kit for about 1/3 the cost!

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2 hours ago, sfdownhill said:

Buzzner, what behavior does a master cylinder with a plugged return port exhibit? I’ve been chasing a soft-levered 5 gen delinked front brake system for ages, bled the system carefully multiple times, rebuilt master and calipers w OEM Honda parts, but didn’t know about a return port or how to check it.

It “pumped up” the clutch. I took it out for the first shakedown ride after clearing and rebuilding the carbs (and other stuff) and eventually the clutch started slipping and finally sticking fully disengaged. On the c-stand, in gear, easily turn the rear wheel. I let it sit for 20-30 minutes thinking it was a heat thing (I’ve had brakes do that) but no change. Finally I cracked the banjo slightly and that released the pressure so I could ride home. I bled it first, thinking it was crud or bad fluid. Also the little metal thing that sits over the return hole was missing and the rubber expandable seal thingy was ajar. 

A second ride produced the same results, so I swapped out masters with my old ‘99 VFRs that’s been in the shelf since the SP1 front end swap. Solved it and I broke down the ST master to see what was up. The return hole is under the solid part of the metal thing (it’s there to stop the return flow from shooting up. Why? No idea. It was plugged solid. I stripped some wire and tried to pass it through, but nothing doing. 

I think I over answered your question, and if it was brakes they would lock solid until you cracked the banjo to release the pressure. 

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13 hours ago, Marvelicious said:

I assume that's the 5th gen Oberon you have listed... drawing some conclusions from their model numbers, the 5th gen - model CLU 3038 - is 38mm while the 6th/8th gen CLU 3036 - is probably 36mm, and is the only 36mm model they offer in their Honda section.

 

Also, has anyone confirmed that the 5th and 6th slaves are a simple swap? I'm thinking in can get most of the benefit of a 36mm Oberon in a used 35.6mm 5th gen slave and a rebuild kit for about 1/3 the cost!

Didn’t know Oberon makes two sizes for Honda - thought it was just the 38mm? 

 

Yes, the clutch slaves look remarkably alike. Even the sprocket cover looks identical between 5th and 6th gen. 

 

Thats why I posted here thinking 6th gen guys could use 5th gen slave for softer clutch. 

 

And to ask if there is anything bigger than 35.6mm to make my 5th gen clutch even softer. 

 

Does anyone know? 

 

Stray

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3 hours ago, Stray said:

Didn’t know Oberon makes two sizes for Honda - thought it was just the 38mm? 

 

Yes, the clutch slaves look remarkably alike. Even the sprocket cover looks identical between 5th and 6th gen. 

 

Thats why I posted here thinking 6th gen guys could use 5th Feb space for softer clutch. 

 

And to ask if there is anything bigger than 35.6mm to make my 5th gen clutch even softer. 

 

Does anyone know? 

 

Stray

Well, it is much appreciated... I just ordered a 5th gen slave and rebuild kit and I'm under $40 on eBay, so I definitely get your motivation.

 

More part number snooping might provide some clues... K&L's application chart for slave rebuild kits lists 5 different kits for Honda. So I think you can safely assume a maximum of 5 different bore sizes and we already know two of them. Operating on the theory that they've gotten smaller (cheaper?) as time goes on, I looked up the 84-85 VF700F and found this which is a replacement piston kit... with a stroke of 26mm and a bore of... wait for it... 38mm!

 

Going back to the K&L chart, here's a list that share the same rebuild kit...

 

CB550SC Nighthawk 1983

CB650SC Nighthawk 83-85

CB700SC Nighthawk 84-86

VF700C Magna 84-87

VF700F Interceptor 84-85

VF700S Sabre 84-85

VT700C Shadow 84-87

VF750C 82-83

VF750C Magna 1988

VF750F Interceptor 83-84

VF750S Sabre 82-83

VT750C Shadow 1983

PC800 Pacific Coast 89-90

PC800 Pacific Coast 94-98

VT800C Shadow 1988

VF1100C Magna 83-86

VF1100S Sabre 84-85

VT1100C Shadow 1100 85-90

VT1100C Shadow 1100 92-96

 

No guarantees, this is just me randomly googling, but it's worth a look. Some of these might share the bore and be a completely different configuration. Still, that's the list I'd start looking at...

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Marvelicious, you’re a LEGEND - thanks for this! 

 

EDIT: unfortunately none of the above have the same style slave as our bikes. Mounting holes and configuration all wrong. 

 

Marcelicious is still a legend, though...

 

I’ve since discovered ST1100 slave is 34mm if anyone’s interested. 

 

Stray

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18 hours ago, BuzznerSuntrusts said:

I think I over answered your question, and if it was brakes they would lock solid until you cracked the banjo to release the pressure. 

Thanks Buzzner. Sounds dodgy - glad you were able to nurse it home. My issue must be something else, probably one last air bubble I don’t know how to find/get rid of.

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9 hours ago, Stray said:

Marvelicious, you’re a LEGEND - thanks for this! 

 

EDIT: unfortunately none of the above have the same style slave as our bikes. Mounting holes and configuration all wrong. 

 

Marcelicious is still a legend, though...

 

I’ve since discovered ST1100 slave is 34mm if anyone’s interested. 

 

Stray

Ah... I see what you mean. Not only are the inlet and bleeder clocked differently (might be able to work around that), but it looks like the lugs aren't even spaced the same. For what it's worth, the models listed for each rebuild kit appear to share bore (and probably stroke) but they don't all appear to be the same configuration. For instance the CB550SC also shows up on the 38mm list:

s-l1600.jpg

 

It appears to be a completely different animal, but it shows that the whole list is worth investigation.

 

 

Also, your info on the ST1100 narrows it down even more. So going back to the K&L chart, we've got...

84 VF700F et al at 38mm

5th Gen VFR et al at 35.6mm

ST1100 et al at 34mm

6th Gen VFR et al at 33.5mm

The only K&L kit we don't know the bore of is the VF1000R, 1200 Goldwing and so on... I haven't been able to figure that out.

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Marvelicious, we might be into something here. 

 

If your 6th gen master plays well with your 5th gen slave then all of us can have the perfect clutch! 

 

5th gen clutch if famously soft with long travel. Some people like that and others don’t.

 

Lots of 6th gen guys say their clutches are too abrupt like a switch. 

 

6th gen master with 5th gen slave might be the perfect middle ground. 

 

One caveat: Apparently the Firehawk guys have the same stock setup as 5th gen and they rave about the Oberon mod. 

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Here’s a chart showing ratios for master vs slave cylinders. Found it in the Aprillia forum, about 1/2 way down:

 

https://www.apriliaforum.com/forums/showthread.php?311989-Master-Cylinders-A-Comparison-of-Appropriate-Application/page2

 

It’s designed for brakes but principle is exactly the same. 

 

 

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Yeah, I'm not sure of the different master cylinder bores Honda has used, but at the end of the day it's all just a matter of mechanical advantage, right?

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My ST11/5th Gen is 14mm while the SP1 is 1/2".

So swapping out the 14 for the 1/2 on the 5th Gen [Which I did, with the same(?) piston] means more travel at the lever?

IDK. I know I like it. I don't think I actually realized the masters were different since the slave cylinders were the same part# 5G to SP1.

I keep reading the description under the chart. Easier to push, but more travel, but easier to modulate...?

So Stray, what are you after? Maybe the 1/2" master is a better fit than changing the piston?

What's the master on the 6G? You'd probably want the "coffin box" reservoir of the stock VFR to match the brake.

 

With the ST11, it was engaging waaaaay out and far too long for my comfort. After getting the return port cleared, it was better, but still a touch too long for my taste. Maybe that's down to clutch wear and not hydraulics? 

 

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Based on a little Googling, the 6th is 12.7mm (1/2"). The 6th gen is definitely a bit unsubtle, which is why the idea of swapping to a 5th gen slave sounded good to me.

 

And a thank you to Buzzner for proving the concept...

 

Stray, are you saying your 5th is too soft? Because going to the Oberon (or other 38mm) slave is going to be softer, as would going to a 6th gen master with your stock slave... 

 

Assuming we have correct numbers, quickest to softest would be...

Stock 5th gen                             35.6mm:14mm  2.54 ratio 

Stock 6th gen                             33.5mm:12.7mm 2.64 ratio

Oberon slave for 5th master      38mm:14mm 2.71 ratio

5th slave/ 6th Master                 35.6mm:12.7mm 2.80 ratio

Oberon slave for 6th master      36mm:12.7mm 2.83 ratio

 

Based on that, I have to assume that if the 5th is known for being soft, there has to have been changes to the clutch itself on the 6th gen because the 5th should be the least soft! Maybe they went to a much stiffer spring?

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You guys are ON IT - good stuff! 

 

My initial motivation for softer pull is the 100 pound clutch springs that are going in the race bike (5th gen). It will be both heavy on the clutch AND a bit jumpy with her bigger rear sprocket. 

 

That means I’ll need a softer pull and better modulation to stop the rear stepping out from a clutch dump. Basically longer travel let’s you feed in the clutch gradually as traction allows. I’m very much a feel rider and use the clutch a lot. 

 

The second motivation was to help the VFR community set up some sort of “master-and-slave-swap” (sounds a bit like an 80’s porno!). 

 

Trouble is I’m no expert and  learning as this develops. I’ve already learned heaps from you guys on this post. If I’m right: 

 

5th gen guys could benefit from a 6th gen slave. 

 

6th gen guys could benefit from a 5th gen master. 

 

Not sure of 3rd, 4th and 8th gen ratios but let’s get the whole party involved! 

 

6th gen guys have the advantage as VFR slaves are crazy cheap on eBay right now! Masters are crazy expensive though...

 

Personally I’m torn between a bigger slave (Oberon) or a smaller master as you suggest. I like the idea of a radial master because that gives even more mechanical advantage over the slave. Not worried about retaining the coffin box look - function is king on a race machine. 

 

Some of those radial Ducati masters are looking very tempting. 

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57 minutes ago, Stray said:

5th gen guys could benefit from a 6th gen slave. 

 

6th gen guys could benefit from a 5th gen master. 

Flip that around... Those combos would be super short!

 

Yeah, a radial master would be pretty sweet, but they do tend to be spendy. I'm seeing plenty of used 6th gen masters on this side of the pond for pretty decent prices, though I'm not sure how bad shipping would be.

 

Little differences in a clutch make a huge difference in feel. Think of it this way... 1" of lever travel (25.4mm conveniently with our ratios) on the stock 5th gen becomes all of 28mm or just under 1-7/64"... 

 

I think some of the European stuff (not sure about Ducati) uses a 12mm master. With the 35.6mm slave that would be a 2.97 ratio... Not sure if that would wind up being too long or not... It might be just the ticket with stiff enough springs, assuming it has enough travel to actuate fully. The last thing you want is to shorten the slave travel to the point where it either starts dragging or slipping!

 

I'm no expert, I'm mostly just playing with numbers here... still, we'll see in a week or two, depending on when my parts show up!

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Also... not to promote the other site, but... 

https://vfrworld.com/threads/brembo-radial-clutch-upgrade-with-pics.44505/

You might shoot CandyRedRC46 a PM if you want some real world feedback about the radial masters. It looks like the radial stuff is actually larger diameter, but changing to radial changes the whole dynamic.

 

Edit: His thread on the same subject here:

 

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I'm running a billet Brembo 16x16 clutch master on my 4g streetfighter with OEM slave. The difference from stock is amazing, in terms of ease of pull, feedback, and modulation.

 

I have a RCS16 master and 38mm Oberon slave for my 6g, but have yet to install them and get miles in. 

 

I've got a TSW clutch slave here if somebody wants to try it. PM me for details. 

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Don't forget that one of the few changes Honda made to the Y2k 5th gen was an upgraded clutch system...

 

Ciao,

 

JZH  

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Interesting... if the info I'm getting from the parts fiche is right, they changed to the later springs and master cylinder, but the slave cylinder stayed until the 6th gen. 

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