Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Clutch pull effort

Just for the hell of it.....because of many threads about excessive clutch level effort.....I put a scale on the clutch lever of my 650 race bike....it had a 6 plate clutch with 750 springs tightened down just short of coil bind.. The studs protrude through the nuts about 4 threads...Venhill Featherlite cable, Emgo alloy levers....The pull reads 16 pounds....Compare this to my 96 Ducati hydraulic clutch at 14 pounds and the 81 750 Honda with a new cable at 16 pounds.....I can pull in any of theses levers easily and repeatedly....
Anyone else ever measure the pull?

Hi Tony -

Interesting....I keep thinking about changing my clutch, pull is a bit stiff (I have a fish scale so I'll give that a try....cable is off at the moment tho), but it's original and works, so if it ain't broke.....

However, I hadn't heard using 750 springs on a 650 clutch with six plates. All the mods I've read about have been the seven plate conversions on 750's with the 650 springs. Is that correct or do I have it backwards based on your post? :confused

Cheers,

Steve

Never measured using a scale like that, but I have found that cable routing makes far more difference than most people expect. I have a stock clutch, with 750 springs tightened to 3 threads proud of the nuts and I used to be able to pull the lever with one finger (index finger). That was until I changed from a cheapo Wassell cable (the nipple at the gearbox end pulled off after nearly 8000 miles) to a heavy duty Venhill cable. Now it is much heavier, though nothing like as bad as many other T140s I've tried.

Last week, we had a ball ramp unit fail in service. This unit is swaged together and the center shaft just pulled through the plate. It was repairable, but we opted for a new one at around 54$ from British Only.
The bike had 750 springs in the clutch.
Those manly clutches take a toll on the whole system.
The 7 plate clutch I recently installed has 500 springs in it. You could pull it with one finger. No slipping. It's a true wonder.

Cheers,
Bill

Any way to identify 650 vs. 750 springs? Must look lighter, are they shorter?

It's a land speed racing bike with about 12-15 more HP than a stock 650....In conversations, John Healy mentioned 6 inexpensive Taiwan cork plates will work quite nicely if excessive clutch slipping is avoided....it does not slip even with the long 4.28 overall gearing for 130 plus mph speeds...less is better if it works...About 6 ounces of ATF in the primary..

For a fair contest we have to standardise on distance from the pivot to the scales' hook.

It’s not an exact science is it!

Tied on like this. Moved the lever out as far as I could, so the string clears the handlebar.



Pulling the clutch slowly shows nothing more than 10 lb.



Once pulled, 5 lb will keep it there.



It’s a 650 with the Mr Pete six and a half cork plate mod. I think they’re 750 springs but they’re screwed out as far as possible without the nuts fouling the outer case. No slip under any conditions.

TT, that's a light pull....... My measurement was 5-1/8 inches from the fulcrum................The feel of the lever when pulled in is also a factor, a smooth "springy" heavier pull beats a mushy light pull.....And hand strength...

You're not wrong about feel. I have more than ideal friction in in the cable, which is at least 30 years old and was on the bike when it went on fire.

But it's light enough that there's no sore wrist nonsense.

I've had clutch problems in the past. Terrible slip whenever oil got onto the Surflex plates. Cork tolerates oil a helluva lot better.

Did my beesa A65 3 spring clutch , measured 5 and 3/4" from fulcrum, just before the ball end, 6.5 kgs , 14.4 lbs to pull in , will hold in at 4 kgs, 8.8 lbs, old fisherman spring balance , possibly the exaggerator model.
Clutch nuts are close to flush with studs, springs stock 650, 6 plates. Cable is home made nylon lined.

Also mind the pivot to nipple distance. The 750 I worked on had 1 &1/8 measured there and we found 3/4" set for a significant decrease in lever pull. The owner has severe arthritis in his hands and this was a blessing for him increasing the pleasure of riding by an order of magnitude.

Cheers,
Bill

yeah, my pivot distance is not ideal, should be 7/8", but its 1 and an 1/8", so it would get lighter with the correct/ unobtanium lever. All the repops are 1.125".
TTs clutch is V light , must try that 6.5 plate dodge, need to wait till the present friction plates are worn down to stuff another plate in, if I try it now the pressure plate will hit the outer case.

Lever on mine is less than an inch from pivot to nipple.

The clutch mod was more work than Mr Pete described, but isn't life always like that!

The thinnest cork mat I could get was 1/32", but even then I had to leave the Surflex lining on a couple of plates to prevent the outermost driving plate falling out of the clutch drum.

And of course the pushrod was then too short.

If spending £100 doesn't have an impact on your life, then buying a 7 plate conversion makes sense.

If you like to experiment, glue cork to the drum and (some) bare driving plates, add an extra steel plate and bend three tabs inward on the last steel plate.

I didn't smooth the cork or the rather scruffy plain plates, so take-up was a bit lumpy, though it's getting better.

Hi Gavin,


I hate to rain on your parade but with 1-1/16" on my T150, 1" on my T160's and 7/8" on my T100, afaict it makes 1% of sod-all difference (unfortunately, I'm not near them to measure the actual pulls ). Certainly for demonstration purposes, I can work all the levers at least several times with one finger, day-long needs two. And I'm not, by any stretch of the imagination built like Arnie, a gym bunny, etc.

Likely the only people who would notice a difference are, as Bill posted, those with real medical conditions affecting hands and/or lower arms.


If you mean the standard '71 levers, from a post by John Healy some time ago, I believe that makes 'em Harris "repops"; if you can find Emgo, they're only 1" (or, if you can only find Emgos, it's the Harris that're 1").

Hth.

Regards,

I also believe that the shape of the lever affects how the clutch feels...In my opinion, stock Triumph levers are not shaped well for riders with smaller hands...

I like it when you pish on my parade Stuart . Appreciate the info, I think the lever fitted currently was a Wassel item, just checked it is defo 1.125 " pivot to nipple centre, a secondary effect of shortening the pivot would be to help keep the dreaded clutch click at bay, the three ball ramp does not like to be over pulled, at the mo I leave very generous slack in the cable to prevent this, one small bonus is that with the lever closer to the bar the initial pull is less of a hand stretch. My clutch does not feel too heavy to me at the mo, but if it got lighter I wouldnt mind, compared to what it was like when I first got it its now a girls clutch.

Just remeasured the pull, first time I had just hooked the lever with the scale, this time I put a loop of string round the lever so the scale clears the bar grip. Halved the value, more like 3 kgs , ~ 6.5 Lbs to hold in. I thought it was lighter . I know it could be lighter still, when I tried my mates T150 clutch I thought the cable had broken, lightest clutch I have ever felt.

I've had some pretty sweet Triumph clutches in the past. Mine is currently a duplex chain unit basket in a pre unit with two chains masterlinked together. Early bladed levers. Very easy pull on it, but the bike makes no appreciable power to speak of.

With other bikes, it's down to special attention to every single component of the clutch, either repair/replace, or modify. Any single malfunction will ruin the clutch action. I was very surprised at the improvement in clutch action when we replaced the ball ramp unit on the '69 TR6. It was also clicking and needed very precise adjustment to avoid. Now, we can't make it click at all. So, now, I'm thinking that a clicking clutch can be fixed with a new ball ramp unit and one that does click is an indication of immanent failure.

On pre units, I have installed bushings in the outer gearbox cover when it was found that there was too much play in the lever there.
Heavy duty Barnett clutch cables always improved the clutch feel. Worn pivot bolts and perches often need replacing or repairing. I have installed the stuffer plate on several bikes, and it does improve things, but the seven plate clutch is the best solution I've seen so far.

Using light weight oil, ATF, or specific motorcycle oil is definitely recommended.

On Nortons, there is a known problem with gearbox oil migration down the center of the gearbox mainshaft. Spraying a little 90w on your clutch plates does nothing for your plate's grip. I haven't heard of anything similar with Triumphs, but when I worked on this custom made Triumph here a little while ago I found a seal installed on the end of the shaft, gearbox side.

There's always something new with these old bikes.

Cheers,
Bill

Bill and TT set me off on a mission, I have a pile of clutch plates and a couple of triplex baskets in the loft.
Dug them out, spent about two hours checking for warped plated and found 7 good flat plates about 75 thou thick all passed the 2 thou feeler test after some tedious lapping to get rid of the burrs on the driven tangs., also found a pile of Surflex plates ( vintage 1990s I think) that are just more than the book 145 thou min thickness. ordered some 1 mm cork sheet. 6.5 plate clutch here we go.
Noted one of the clutch baskets is a subtly different construction from the others, rather than being constant thickness around the rim it is relieved between slots on the OD, sprocket teeth still reasonable and not badly notched either, put it on the scales , 50 g , 2 oz lighter than the regular basket. mmmm.
So my plan for the lightest clutch I can possibly achieve is to do the Pete R thing, machine off the ID part of the Surflex friction lining to move the effective radius out. And hope that the whole stack of old worn flat plates is thin enough to fit fit.
I have some brick cleaner H Cl acid ( Muriatic ?) which will be used to give all the glazed steels a more bitey surface, 20 minutes dip to etch is supposed to do the business, dangerous chemistry to follow.
Whats the best way to clean old friction plates? any ideas.
Re the 3 ball mech, I spent a load on a refresh of this part, and was dismayed when the unworn stuff still clicked, wasnt until I learned about the different lever pivot distances that the penny dropped, the 1.125" pulls the 71 mech too far, slackened the cable, click begone.

If your clutch is oily, cork will grip much better than any other lining I know about.

The surprising thing was how easily Surflex lining can be removed. Most segments could be picked off with a thumbnail. Some needed a penknife.

6 cheap Taiwan friction plates shaved like this, running in ATF, gives zero slip with the man springs on the race bike in my OP.. Or do what TT did with the 1/2 plate...

Hi All, I find the whole clutch & clutch cable issue most interesting & for old weaklings like me with arthritis it can really effect enjoyment of the bike.

I'll relate some of my experiences if I may. Most interesting how different others experiences can be.

Regarding 650 & 750 springs the 750 spring wire diameter is greater. Also 750 spring is shorter. The factory 750 spring is way stiffer. A 650 spring I can compress a ways with my fingers. 750 spring I can hardly compress.

A factory 750 spring is about 1 3/4" long with wire dia. aprox. .112"

A factory 650 spring is about 1 13/16" long with wire dia. aprox. .098".

Oddly neither spring matches length spec in workshop manual. This is with new springs.

I have many used springs on hand. Oddly they have not taken a set, meaning the old springs have the same length as new springs which I find rather odd. I guess the quality was good. Testing springs with home made tested on bathroom scale, comparing to new, they don't seem to loose tension either.

I bought my '73 Tiger new. A few years ago I installed Hyde 7 plate +1 kit. The original springs had not lost length, tension showed same as new repro springs.

Has original lever & perch. 7/8" pivot.

Some parts sellers sell 650 & 750 springs as being the same. They are not!

I became interested in springs due to my clutch cable broke 4 times with either the upper or lower ends pulling off. Venhill featherlite cable was no more durable than genuine Triumph. I didn't try Emgo cable.

After much research I found Barnett cable has swaged steel ends. They are much stronger at the attachment of ends. So far the Barnett has been the only cable to hold up long term.

Regarding friction of cable, I have only used motor oil for lube. I keep cable, lever, cable ends well lubed. I lube cable with bag of oil suspended like photo in workshop manual. Takes several hours to get clean oil flowing through. I usually leave overnight.

The Featherlite started off good but after a few thousand miles the inner liner deteriorated & started balling up causing much friction. The upper end pulled off. I used no lube on liner as Venhill said do not lube.

Barnett cable lubed with Mobil1 v-twin - oil is every bit as friction free as Featherlite was, but again has held up well.

A well lubricated cable cannot be overstated. A friend of mine had Barnett cable installed a few years without lube ever. Was ok at first, but had gotten hard to pull. Lube with v-twin oil & the bag made lever about twice as easy to pull. Truthfully I was shocked. This was just a few weeks ago so very fresh in my mind.

Back to springs... I wanted to not only stop breaking cables, but my hands have developed arthritis after a life time as a mechanic. I need easier pull.

My first attempt was to replace 750 springs with JRC brand 650 springs tightened to studs flush with dome. Then going tighter a little to adjust wobble. Prior I'd adjusted 750 springs same way.

This dramatically reduced lever effort, but I was experiencing some clutch slip riding 2 up which I ride 2 up often.

I put 750 springs back in. No more slip.

I have always used Mobil1 V-twin 20-50 oil in engine & primary as they are shared. V-twin frees clutch well & no slip.

After more research I installed Hyde 7 plate +1 kit. Reinstalled 650 springs tensioned to stud even with slot not dome. Then went deeper on 1 & out on another to adjust wobble.

This has given me very easy lever effort & no slip.

Back to the '69 Bonnie. Installed Hyde 7 plate all new steel plates also, Hyde brand. Experimented with different oils. Torco 20w didn't release as well as hoped. Tried ATF F. Released well, but was a little grabby on take off. Mobil1 V-twin. Worked well but owner wanted to try ATF again.

At work I discovered over a period of years ATF of different types & even different brands of same type can have very different friction characteristics. Strange but very true.

This time we used genuine Mercedes Benz ATF 134 (basically a semi synthetic Dexron). This has been best yet on '69 Bonnie. Very easy freeing of clutch, no slip, yet very smooth take off.

From my experience at work this friction is very similar to ATF shell 134 or Pennzoil Dexron IIIO, or Pennzoil Dexron VI. All of these are good at lubrication of metal parts such as chain & roller bearing, yet don't increase slip.


From what the Pennzoil man says the difference between ATF F & Dexron is Dexron has friction modifier such it allows softer grab of plates. My experience shows that to be true in real life. I don't know about ultimate slip, but Dexron family seems to not slip on our bikes.

Regarding 3 ball ramp another friend recently replaced ramp & it really helped release. The pivot was worn bad where pin goes through.

I've been involved with several Hyde 7 plate kits now. I've become a believer in them. Aerco makes a 7 plate also. I have no personal experience with those. I don't know anybody that has installed on. 1 person reported positive results on the group.

Fun & interesting stuff!
Don

I did away with the innermost plate, in that the series is: cork lined back of basket- plain driven plate- lined driving plate and so on.

Be more interesting with a image of your scale reading

Hillbilly....I just noticed from your photo that you are shaving the inner, but have also gripped the inner.

I would have thought you would clamp on the outer to shave the inner......or do you leave the steel part of the plate the same width and only remove bonded material???
Which means you carry unneeded weight I guess? But the photo looks like you are removing some steel/reducing the thickness of the plate?