Another slave clutch bleeding issue... and yes, I did much searching

Many, many useful tips on the forum but I'm still stumped on my clutch slave.

I have only had the bike for a month or so, only one ride and it rode well but I noticed a bit of creep when stopped with the handle pulled but in first.
So, ordered a kit for an 85 vfr500. It did not fit. The old seal seemed larger than the new seal (even with expansion taken into account). \installed anyway but when trying to bleed, I would hear a slight sucking from the CS so I contacted the parts guys with the measurement of the old seal. Looks like the P.O. may have swapped a slave from another VF model.
The parts guy kindly sent me a seal from a 750 (thanks, PERFORMANCE International in Costa Mesa). But I tried that today and it is too wide? Looks to be slightly wider, when compressed, than the bore.

O.K. back in with the old one. Bleeding all morning and getting nowhere. I can build up pressure but not enough to disengage the rear wheel when in gear.

Cracked the upper banjo already. When I squeeze the handle, I do see a bit of ripple in the reservoir. The reservoir does go down when I open the bleed. No leaks anywhere.
I remove the slave and squeeze and the piston does move outwards a few mm at a time. There are no fluid leaks at the piston. I push the piston in by hand and the fluid increases in the reservoir. Is this a symptom of a weak master?
When I crack the bleed, I get constant micro bubbles. I am not sure if those are stuck in the fluid or being sucked in from the bleed hose but I did check that constantly. If I had NO air bubbles, I would suspect the master.
So now, I have clamped (taped) the handle down for overnight with the hope that any air moves upwards to the upper banjo.
Any other suggestions? What is the C clamp method?

Thanks and sorry if this is repetitive.

Peter

 

More mysteries to solve: Tried and tried to bleed with a new kit (k%l) but it seems as if the seal is too small as I can hear air working its way around the seal. I contacted the seller, wondering if the P.O. had replaced the slave with one from another Honda. he sent me a seal for a 750 which is too wide for the bore.
The inside of the slave is identified as MF2, which Honda says is correct.
Ordered a Honda original part and the seal seems similar or maybe even a bit smaller than the one from the kit that leaked.
I feel a bit of uneven surface in the bore and am wondering if the inside has disfigured over time. No corrosion or pitting that I see, just a ridge.
Most of the ones for sale on Ebay look beaten up and may not be in any better shape (as I would have to put in a new seal anyway), are there any other slaves from other models that I can fit to a vf500?
Any other suggestions?
Thanks

 

I think I remember the seals are not symmetrical (just like caliper piston seals). It has a slight taper. The wide end should enter the slave first upon assembly (just like calipers).

 

Yep, they are tapered with a fold and the wide side (looks like a skirt) goes on the inside so the oil pushes against the inner groove to swell out the sides but i am feeling a slight ridge inside the slave. The stock seal, from Honda and K&L both seem way too loose although the MF2 slave body is stock for the 500. Frustrating stuff to deal with as Honda doesn't really have any answers or sell clutch slaves (in Canada). If anyone out there has one off their bike and apart, have a look at the inside and let me know what your stamp is. There has to be a simple problem, or..... maybe one of the other seals does give enough pressure and my plates are stuck from 2 weeks of sitting? Probably not as I did hear air sneaking by the new seal when pumping the slave. Just grasping at straws at this point.

Thanks.

 

How many miles on the bike? Bore should be the constant, perhaps it is worn beyond the service limit.

 

34xxxkm/22xxxm or close. I will look up the bore measurement. Anyone know if a slave from another VFR will fit this bike? The slave kits are a bit confusing as one will claim to fit the VF500 and 700, 750 but Honda says it is another part number.

 

Hi guys, just picked up a nice 1983 VF750F to add to my collection, runs beautifully etc. but has a leaking slave cylinder. Thought I might add a few comments to your thread as I am right in the thick of finding out why the leak and beginning repair on the slave myself and it seemed appropriate to comment. The bike has about 30,000 mi (54000km) on clock. On dissembling the unit, it is quite apparent why the leak. Hope the pictures demonstrate the scratched and pitted piston, worn edge on the seal and slight scratching of the bore which I have already lapped with a bit of 1200 wet n' dry emery paper. It really requires honing for a better result though.

The first thing I noticed was the lip at the entry to the cylinder bore- is that meant to be there? My feeling is that it is , and prevents the piston from popping out when you remove the assembly from the bike- I will ask my Honda mechanic when I pick up the new seals! The lip seal/cup itself definitely worn out and rounded, and the piston is corroded. My approach will be to hone out by hand the bore, smooth off the piston external diameter, replace both oil seal and cup seal on the piston, and try it out.

As far as your issue is concerned, I suspect a mismatch in parts is the problem. The new cup seal should be slightly difficult to fit and might seem oversize at first glance, my feeling is that one almost needs a sleeve like a ring compressor to compress the cup on the plunger/piston to make it easier to assemble, and remove the possibility of nicks on the seal (it would be easy to make a simple sleeve to do so out of shim or even an old beans can). This seal is obviously meant to be quite snug when assembled, after all, like brake caliper seals, requires compressed air to get the piston to pop out of the cylinder.

Just to add to my previous post, I would be surprised if these clutch slave parts did not suit a range of bikes from that era, as do many others. The parts number I ordered for the cup seal was 22865-MB0-003 1243872. Does that align with your part? Cylinder diameter is ~34mm and piston ~33mm, I dont have a micrometer and cant find my vernier for the moment.

 

I will measure mine as well and try cleaning it out in case there is a coating of dry stuff in there (no rust that I can see). I am curious if the clutch slave body on the 750 has the same mounting points as the 500. if so, I should be able to find a good 750 slave as the ones for the 500 seem more rare and what I do see is expensive as--is crud (so, no idea if it is better or worse than mine). What number is stamped on the bottom of the bore?

 

I thought you might ask that! Unfortunately, there is no number inside or outside the bore .... once I find my vernier, I can measure up the mount point and diameter of the housing and will post later. The Honda parts listing for the VF series does not show a part number for the housing either, only for the components- strange! I would hate to think what a complete assembly would cost too. In my case, I think just a rejuve (light hone with wet n dry) plus new cup seal will do the trick..they are not that critical, although Honda do specify a wear limit, that I haven't checked.

FYI, the hole size of the gearbox case where the slave cylinder fits is 50mm

 

Just found my vernier, the piston is 33.5mm, bore size 33.6mm, the engine housing into which the slave unit fits is 49.8mm and the land on the black of the slave cylinder is 48m. So, the slave is only loosely located I suppose as it is centred on the clutch pushrod. There does not appear to be a gasket. Hope that helps!

 

I'll have some stuff to add to this conversation, but don't have time right now. But...
Pretty damn sure there is not supposed to be a lip. I have a bunch off of bikes that I will confirm with.
There is a gasket, but it doesn't really do anything and won't affect anything if it is missing.
It should not be "loosely" located. It should have 2 dowels that firmly hold it in the right spot.

 

Ok, well maybe my VF slave is off another model...that would be ironic! Will follow up both issues... the parts list I have definitely doesn't have a gasket and there are no dowel pins locating the housing. This tells me the VF unit is not equivalent to VFR

 

OK... Hold on! Beeton... we are talking about a VF500F, right?
Glenn... you are posting VF700/750 fische pages.

 

Sorry guys... yes my bike is a VF, the post was more on the cup seal tightness issue... the slave cylinders might be different. I desist for now

 

100% should not be a lip on the inside bore of a VF500F slave. (or a VFR700/750F)
The 1986/1987 VFR700/750F uses the same slave, it just does not have the "Hydraulic Clutch" plate. MF2
VF700/750/1000/F/R is a different part.

 

His is a "VF" too... but a 500. He does not have a VFR500, as there is no such thing.

 

Glenn... your unit is pretty bad. Should also not have that lip and your piston is (obviously) pitted. That steel piston (with pitting) has worn your aluminum slave.

 

Thanks for the comment Captain 80s, thats the info I was hoping to get! I took another look at the housing, it "appears" there is a lip, but on closer inspection it is just where the where the seal stops moving outwards I think. I will get a new piston and hope the scratches are only skin deep on the bore.

 

use green scotchbright to clean any ridges or imperfections on the piston or bore.

 

Hi Guys, as it so happened, I picked up a nice brake cylinder hone from Supercheap Auto (great source of all things automotive) and honed the cylinder bore then finished off with 800 wet n' dry paper- it came up like new! I also ordered a piston, oil seal and cup seal from local Honda dealer, but on inspection today, to my dismay, the new piston was oversize by 3 mm and the cup seal likewise- what the f---.

The parts list above is correct for the 750 but incorrect for the 1000. The parts guy told me that the 1000 cylinder is labelled as shown in my pictures whereas the 750's are not- interesting. It seems some dodgy operator has exchanged the original slave assembly for one from a VF1000- needless to say I am learning fast! Anyway, a little judicious use of abrasive paper did rejuvenate the piston and I am awaiting the correct cup seal. Checked the travel on the piston and the cup seal is well back in the cylinder, so it should be fine and have enough stroke to work properly. I will post in due course! Before this work, the clutch was indeed operational, but leaky, so I expect similar performance in spite the cylinders being slightly different.