Slipping Clutch

Ladies and Gents,

I have just completed a comprehensive restoration of my son's former 1996 VFR-750. It was repainted with new decals, tank rust was removed by a local restoration shop, and the carburetors were professionally cleaned and rebuilt, with another thorough cleaning by me. After fixing a couple of annoying stuck carb float issues, the bike is running very well. All the fluids were changed, all new coolant, oil and filter, etc. The bike looks almost like new.

On the test ride today, and after a fuel fillup, the clutch began slipping about mile five from the house. It grew progressively worse, and I returned home. The final two miles home, the clutch was slipping so badly that I could use only 1st and 2nd gear.

The clutch engagement range is very tiny, almost at the very end of the clutch lever all the way out. It has the characteristics of a stuck slave cylinder, perhaps?

Any ideas? Is the clutch pack relatively easy to replace?

Cheers,
Mike Shelton
Stafford, VA
1996 VFR-750

 

Mike you might have a bit of debris lodged in the tiny return port at the master cylinder. I'd clean that out first, then flush the clutch line and bleed, before I worried about the clutch plates themselves.

Actually replacing fibre discs is pretty easy, on my 5th gen I worked on the sidestand and didn't need to drain the oil. You will need a fresh clutch cover gasket, the fibre discs and for good measure some new springs. Disassembling the clutch is as easy as removing the 6 bolts that hold the springs in place, then slipping the parts out of the basket. Just pay VERY close attention to the position of any washers in the clutch, and to the sequence of the discs. Use a torque wrench on the spring bolts, bad things happen when these are over-tightened.

 

Cadbury,

Thanks for the quick reply. I did use a Mity-Vac to flush and fill the brakes and the clutch with new fluid, but I'll check again and look at that return port.

I replaced the clutch on a Ninja 1000R many years ago, and it was quite simple, so if needed, it sounds like the VFR will be simple also.

Cheers,
Mike Shelton
Stafford, VA
1996 VFR-750

 

12 August 2016

OK, here's an update. This morning, I did a complete fluid change and flush and removal of all the debris and crud in the clutch slave cylinder. Used compressed air to gently blow through the line and bleed port. All the new fluid came through clear as I completed the job.

Just returned from Test Ride #2, and the clutch exhibited the exact same traits. OK at first as it is cool and warming up. Zero slipping, nice and tight. About ten to fifteen minutes into the ride, the clutch began slipping as I was climbing a slight rise in fifth gear. This was in the general direction back to the house, so I kept going. The clutch lever feels fine and I detect it is engaging at the same point, but slipping badly.

Here's some background. I received the bike back from my son in March. It was his first (and only) motorcycle, as a college gift, which I purchased used in 2000. Because of family and his busy schedule in the Navy, he was no longer riding it. The bike had not been ridden in about three years. The carbs were gummed up and the bike would not start.

I had the bike apart, down to complete removal of the forks so that I could R&R the spark plugs and do a complete cleaning of the radiator system. The fairing parts and tank were repainted in the OEM Honda Red, forks rebuilt, new front tire installed, bike was reassembled. Started it up and after thorough warming, shut down and changed the oil and filter. I used Shell Rotella 5W-40 synthetic oil, which I have used successfully long-term in three previous Japanese bikes and in my BMW R1150RT (dry clutch). I have about 320,000 miles using this oil on four motorcycles, three of them with oil-bathed clutches. Never had a slipping problem on the Jap bikes. Rotella is good oil.

I just wonder - is the VFR hyper-sensitive to synthetic oil? Or, are the clutch plates glazed over from long-term non use? Mebbe the clutch plates are worn? The bike has only 29,245 miles on it and I know all its history since we bought it at 9000 miles used. It has never been abused and raced, and my son had a low-speed low-side in loose gravel several years ago which scratched the paint left side.

I can think of no other causes for this issue. I'm outta ideas. I don't wanna opt for a new clutch pack and the associated work unless I have no other options.

Thanks much in advance for anyone's consideration.

Cheers,
Mike Shelton
Stafford, VA
1996 VFR-750

 

No, you should not have any problems with synthetic oils as long as they meet JASO-MA/MA2 specifications (no friction modifiers). Suspect young person first.

 

Maybe some more diagnosis is needed. Can you take another ride until the clutch starts slipping, and then break open the bleed nipple and see if there is any built up pressure? If not I guess that would rule out hydraulics and point towards worn plates.


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Cadbury,

Good idea. I'm about to go do just that. The bike has not been operated in about 30 hours, so if the clutch has returned to normal, I'll see if it does this again for the third time, then crack the bleed nipple and see what happens.

Thanks for the assistance.

Cheers,
Mike Shelton
Stafford, VA
1996 VFR-750

 

The crud in the return orifice is in the master cylinder, not the slave. It is a tiny port located under (sometimes) a shiny metal plate visible when you remove the master cover. The shiny plate must be moved in order to clean the return orifice with a thin steel wire, e.g. electric guitar string

 

14 August 2016

Kenny,

Thanks for the clarification. I rode the bike again yesterday, and it was much better. It took longer before the clutch began slipping, but not as bad as before. Once it became prevalent, I stopped, and cracked the slave cylinder bleeder. It produced a very small squirt of fluid and some bubbles. Re-tightened, and then rode another 15 miles with all sorts of up and down shifting, revving up to 9000 rpm. The bike also does amazingly smooth clutchless upshifts, so I did that some to mitigate the issue at the beginning of the ride.

Bottom line - when I returned home, it had stopped slipping, but the engagement friction zone was still a bit too far out.

I have thin wire - I'll use that today on the port, and also change the oil again.

Thanks for your, and everyone's, help. The bike is looking primo, and the new paint really pops.

Cheers,
Mike

 

I would have thought the clutch springs would have been able to push any crud through the return hole, problem occurs with the brakes because it is only the "O" rings in the caliper that pushes the fluid back into the master cylinder and that is why it blocks and the amount of fluid travel in the brakes is minimal compared to the clutch slave cylinder

 

The pressure plate is being held 'open' by the fluid pressure in the line pushing against the slave piston and push rod--that's why the clutch is slipping. So the springs aren't moving nor are they able to move--the force that compressed the springs is still holding them with no release possible, i.e. the return path is blocked.

Another culprit is delamination in the inner layers of the 20-year old rubber tubing.

 

Good stuff. Attention should be paid to the post aboot former riders, owners ect. Specifically here that someone may have been riding the clutch for many miles. In this case an unknown but in many cases a distinct possibility.

LOL, Rotella seems to be holding its own..

 

17 August 2016

Hi all - thanks to KennyBobby, BadBilly, NormK, et.:

Here's an update -in between all the other distractions and shiny objects I've been chasing, I did a complete check of the clutch plumbing and did one more flush and fill of the clutch fluid. The only thing I have not done is to remove the master cylinder piston and seal to look at that. But I am sure that assembly is good and I'm not gonna remove it.

The return orifice in the bottom of the reservoir is clean, and a piece of wire stuck in that hole encounters notches and resistance as the clutch lever moves the piston rod in and out.

To reiterate, the slave cylinder was removed and thoroughly cleaned. It's not the problem - everything in there and the rod moves freely.

Soooo - following my fourth test ride today, of about 10 miles, the clutch is still slipping, not as bad. But the traits and mannerisms remain the same - OK when cold and first riding away, but as the bike warms up and the coolant gauge stabilizes, the slipping reappears. The clutch lever feel is good and modulates well.

I can only conclude that the clutch itself needs replacement. I did some research and watched some VFR YouTube videos, and I'm convinced that the plates need replacement.

Fortunately, the eight plates are only about $10 each, and with a new gasket, I can have Honda factory plates and gasket to my door for about $100. The actual repair looks quite straightforward, although it's more time that I don't have. But oh well.

Thanks everyone for all your help. Any additional info or wisdom tidbits on the clutch replacement will be appreciated.

Cheers,
Mike

 

I did a clutch disc and spring replacement in my 5th gen earlier this year, using EBC-brand parts; my clutch at 94000km was getting a bit shuddery on take-up. It works beautifully now.

I was able to do the job on the sidestand without draining the oil, but (obviously) you don't want to drop anything into the sump, so I stuffed rags into the cavity while I was working. The gasket might take some breaking loose, and I used a plastic hammer to get it moving. I was able to swing the clutch cover out of the way and cable tie it to the radiator, without disconnecting the pulse generator wire.

The clutch disassembly is as easy as pulling the bolts and springs out then sliding the clutch lifter plate out, then sliding all the discs out. When you come to reinstall, there are two slim spring washers that go in, the flat one is first, then the dished one concave out, then the fibre discs. One fibre disc has a bigger id, that goes in first.

The clutch bolts don't need much torque (12 N-m) and apparently the clutch outer threaded portion snaps off easily if you over-do it.

Cleaning off the old gasket material was the biggest pain, and I used a scraper with a razor blade, gently so as not to gouge the alloy case. It has been suggested that greasing one face of the gasket prior to installation would make future removals easy. The rags in the cavity will stop gasket debris from getting into the sump.

I found that while I was working on the clutch, the slave cylinder was extending, and allowed some air into the hydraulics, which was very obvious from the first squeeze, so you will probably need to bleed the clutch. I suspect you're getting good at this by now. I also pulled the clutch pushrod right out and polished it up before some grease and re-installation.

Best of luck, hope this cures your slipping clutch.

 

i hope the new clutch disks cure the problem.

Earlier you said:

When the engagement is so far out on the lever it indicates to me a fluid issue such as the blocked return hole, or delaminated tubing. The tubing shreds apart internally and acts like a one-way valve that let's the fluid down to the slave but not back up to the master.

 

Cadbury,

Thanks much for all the info. Very helpful. My VFR has only 29K miles.

I will order the Honda OEM parts today - it's all available according to various web sites.

The restoration has produced a beautiful bike. When the clutch is replaced, it will be a 100% all-up-round and ready for eBay and Cycle Trader for sale.

Cheers,
Mike

 

29 August 2016

Fresh Update:

The frustration continues. The new clutch parts came in, and I installed the nine new clutch plates and replaced the five springs with new ones. The engine cover gasket came off just fine and the entire process was easy with no drama or surprises. The metal plates between the clutch plates looked fine with no bluing or heat damage and all were flat and straight. And I changed the oil with fresh Pennzoil non-syn 10W40.

Some of the clutch plates showed wear, other looked like the new ones, so that area was indeterminate to me. The clutch basket and the entire area were incredibly clean, no signs of clutch plate debris, no sludge, nothing. Just real clean.

Soooooo, I took it for another test ride, about 15 miles, and same thing as before. The clutch is just fine as the bike is warming up during the early part of the ride. Near full-open throttle in higher gears produce no slip, but as the temp gauge heads to the normal spot, the slipping begins again, and it remains that way the rest of the ride home, using the clutch for normal shifting and also doing nice, smooth, clutchless upshifts. No matter what, the slipping continues.

I'm outta ideas. The bike is beautiful and finished and I have a buyer who wants the bike bad, but I can't give it to him until I get this clutch issue resolved. I will take it to the local Honda dealer today for them to find the cause, which remains a mystery to me. It assuredly has a cause, but what it is, I dunno. The only things I have not done is to replace the clutch line to the slave cylinder, or to overhaul the master cylinder with a new piston kit.

Any more ideas? I am all out.

Cheers,
Mike

 

Back the bolts out a bit on the slave cylinder to make sure the pushrod is not loaded, then try that and see what happens once it warms up

 

Not a bad idea, but I would wonder why that would work? Hmmmm. Never know.

Since I was in the general area this morning, I stopped at the local dealer and spoke with one of the long-time mechanics there. First, no quick fix because they are backed up and could not get to the bike for at least a week. And I leave soon for Reno.

We spoke a bit. Naturally, the shop has no master cylinder rebuild kits in stock, nor clutch lines. But he asked some good questions, and he recommended that I remove the plunger/piston and seal from the master cylinder for inspection and cleaning. As some have suggested here, he surmises that I may have a small clog or obstruction in the master cylinder plumbing. The shop would basically have to replicate most of the same diagnosis I have done.

I'll also drain the fluid from the clutch line and take compressed air and blow through the line as best I can.

It can't be the clutch. It has to be somewhere else, since the exact same symptoms occurred with the new clutch.

Egad.

Thanks,
Mike

 

If you don't have enough clearance on the rod, as the motor heats up the rod expands and puts pressure on the pressure plate, the rod is expanding at a greater rate than the alloy casings