My 78 TR7RV came with a seven plate clutch installed when I purchased it almost 4 years ago. Last year I inspected and cleaned the plates which were not quite ready for replacement. Figured I had one more season on them. So now I'm looking into replacing the clutch and wondering if I should go with a new 7 plate or return it to a 6 plate clutch. Reading the forums makes me think that a well adjusted 6 plate clutch works perfectly well, and that most folks are running a standard 6 plate clutch. I find very few vendors in the U.S. that sell 7 plate clutch kits, and when I do, they cost more than twice that of a 6 plate. I am familiar with clutch drag, slippage, and hard pull. I've changed the cable to a Featherlight and replaced the RED heavy duty springs with stock T140 springs. I do experience a bit of slipping in 5th gear but think another half turn tightening of the spring nuts would most likely cure that. So, is a 7 plate clutch necessary and worth the extra cost?
Many thanks!
Are you sure there's any significant wear on the linings? They must start out pretty thin.
Wear on my own bikes' clutch friction materials has been so slow that they practically last forever. After all, we don't go around slipping the clutch.
If I read the rest of your post correctly, your 7 plate clutch is slipping, so you want to fit a 6 plate clutch. That is perverse.
I don't understand how a 7 plate clutch can slip if properly adjusted, especially with t140 or stronger springs?
I have a featherlight/ 7 plate clutch /t120 springs and an alloy pressure plate.
My bike is "pepped up" from a standard bike with half race cams and 8.5 Pistons
It doesn't slip.
The plates should last a long time if a decent brand.
What oil do you use?
In the uk standard plates are about £9, 7 plate type about £11/12
I use a 6 plate clutch without any problems and have done since 1978 .Just replaced it a few weeks ago as i had some spare plates sitting on the shelf and i was rebuilding the centre anyway.Not many sellers at the places i attend througout the year offer the 7 plate version.I paid £4.50 a plate for mine.
I would expect,with a clean up,your 7 plate will still be OK.Scratch up the plain plates a little and rinse off the friction plates with a mild degreaser or even washing up liquid.
I like Barnett friction plates and have used their springs too. The only time my clutches have ever slipped was when I used car oil. I clean old plates with a soak in diesel fuel and an overnight drip dry. Bob
My question is.... When it is time to replace the clutch plates, is it worth the extra expense of a 7 plate set rather than 6 plates?
Here in the U.S. very few vendors sell the 7 plate sets, and those that do charge twice as much as a 6 plate set. Seems to me the vast majority of people are running 6 plates. If that's the case why spend $140 for a 7 plate set, rather than $65 for 6 plates?
Is there any real advantage? Read the forums and you'll see that 7 plates can slip just like 6 plates.
If,like mine,the 6 plate works very well and no sticking with hardly any noise when selecting 1st,i would just keep using a 6 plate as,i still do.It might be just the way they are set up that determines how good it works.It appears that plates get stuck more often in the USA for an unknown reason as mine has never stuck.Since my clutch plate replacement recently,including plain plates,i have got a better 1st gear engagement.It is the first replacement of the plain plates so maybe replacing all the plates cures the crunch.Only difference in my case is the old ones might have had tang wear which might make a difference.
This complete plate change has the clutch working the best it has ever been so worth paying a little bit more.Cost was under £50 for all plates.I buy these at autojumbles so they are unknown makes.
If you replaced a worn 6 plate with a new 7 plate,it is certain to be better but i wonder if the same could also be achieved by using a new 6 plate.
I do prefer the use of an alloy cover plate over the steel pressed type.When i fitted one about 15 years ago,it did make an improvement although i cannot explain why.
Hi PMeridith, Yes they are worth it. But the 6 plate works good also. The main advantage of 7 plate is less lever effort & better release. The less effort comes from being able to use less spring tension. Installing stronger springs voids that. Still a 7 plate grabs better than 6 plate. Even Triumph went to 7 plate in later years. It should not slip with 650 springs. 750 springs are much much stronger. It for sure shouldn't slip with 750 springs. Where are your nuts now in relation to the studs? I really like Hyde 7 plate. I've not used the other type 7 plate like Bonneville Shop sells.
Look over the "Bodge! not happy" post for plate thickness. When new they look worn out.
Don't do any thing else yet. Things are not adding up here. What kind of oil are you using?
On a side note, with 750 or heavier springs you should expect the clutch cable end to pull off. Carry a spare cable (not kidding). I've found only Barnett cables can take the strain.
Don
As Don says,the 750 springs are hard to work.I used them for a short period and it hurts the fingers if running in traffic for any time.I think i had a cable end break off too.When my cables fail,it is usually at the gearbox end.Always have the clutch cable loose with no ties to the frame.I might do a short video of my 1st gear selection without it crunching.Very unusual for it not to make any more noise than just a click now.Of course,it is hard to video as two people are needed but i do have a wife for that.My assistant mechanic who is now quite good at spanner work.
Thanks to all for your thoughts. For the record, I'm running Valvoline 20w-50 motorcycle oil. My clutch pull is good even though I have t140 springs (57-4644). My Venhill Featherlight cable has an unrestricted run. About 1.5 years ago I cleaned the friction plates and scuffed up the plain metal plates. The pressure plate has been adjusted to where the top of the clutch pins are just below the top of the nuts. It's my thinking that perhaps another half turn of tightening on the nuts may resolve the slight bit of slipping I experience when I kick it down in 5th gear.
So it sounds like Rambo and Coloradobob are happy with 6 plates, while others like TR7RVMAN, TT, and DaveM see the 7 plate version as having an advantage even at twice the price. I'm still on the fence.
If you get slip with six plates, you'll have wasted the price of the plates and will no doubt then spend the price of new plates for the seven plate kit.
Springs insufficiently tensioned cause slip, on any clutch.
"Springs insufficiently tensioned cause slip, on any clutch."
TT, that's exactly why I am hesitating to spend the extra money on 7 plates. Slipping can happen on any clutch. I think it's more about adjustment / tensioning the springs rather than the number of friction plates. Certainly the vast majority of t120 and t140 on the road today are running with 6 plates. If slipping was an exclusive condition of running 6 plates, don't you think most of us would now be running with 7 plates?
Well, give yourself an easy cheap life by tightening the springs and then leaving the clutch alone and riding the bike.
Unless it still slips.
Other people's experience is misleading. Some people report no slip, drag or heavy pull with the original clutch. Why? Some of them are just lucky; some of their clutches aren't as original as they think; some of them never use more than 1/3 throttle; some of them don't ride their bike; some of them are even stating a falsehood.
Im using a six plate barnet set with new stock plain plates. Softer springs, no slip. Stay away from the "alto" plates (orange) They will happily slip right out of the package I had a set of stiff springs and it was a workout in stop and go traffic.
Hi PMeridith, Again, the main advantage of the 7 plate was to get easier lever pull by allowing you to run softer springs or looser spring adjustment. A side benefit was they tend to release more freely so shifting may be better. For sure finding neutral tends to be easier.
I'm sure you rod adjustment is correct. Would be interesting to measure how far the top steel plate is from the edge of chain wheel. That is the fitted total stack height. The measurement gets larger as plates wear. If you had a base measurement with new plates, when worn you could run nuts in equal to the wear of stack height & that would maintain spring tension of a new clutch. Normally on a new 6 plate I start with dome of nuts even with studs. Then back a nut in & a nut out to get no wobble. So the average is still even so to speak.
As you know 750 springs are shorter & much stiffer so going in with all 1/2 to 1 turn can make a big difference.
However... If it was my bike I would for an experiment change oil to Mobil1 v-twin 20-50. Ride bike a few hundred miles & see how it effects clutch. Seems there is a difference between motorcycle oils on how they effect Triumph clutches. I've been finding v-twin gives better friction than ATF fluid, yet frees as well. Plus v-twin is very good lube for chain & slipper blade. My hunch is within 200mi. or less v-twin will cure slip.
A fast easy way to change primary oil that gets almost all of it out is siphoning. Get a 1/4 brass tube. Cut it to 9". Hook some clear hose to it. Stick it down primary filler plug behind chain & it will go all the way to bottom. Suck on hose & siphon it out. Do it after a good ride so oil is hot. Refill with 250cc motor oil. Leave some room in frame for any extra primary oil to self level. Get a 3 pack of Gerber baby bottles from grocery store. They are marked in oz & cc. Ace hardware sells the tube & clear hose. Always clean eng & frame screens at every oil change. I change oil every 1k miles.
Again all, thanks for your thoughts. TR7RVMan, yes, rod adjustment done with cable completely slackened. I will try your suggestion with Mobil1 20w-50 in primary and see if it makes a difference. If not I'll pull the side cover off and unless the friction plates are too far gone, will clean and replace and slightly tighten springs and see what happens.
Hi PMeridth, You have to change all the oils, meaning primary, eng sump, frame oil. The primary oil slowly exchanges with the frame oil so primary oil would be diluted by the old eng. oil in 20 miles of freeway driving.
If you have to pull primary cover measure the stack height. I posted it the prior post I mentioned. That is will all new plates. 6 or 7 plate will stack the same within 1/64th inch. Some after market 6 plates are really fat & almost make the last steel plate fall off the drum with clutch is pulled. Plus rod adjuster nut can hit the inside of the inspection plug on primary. The adjuster is really close on the 750s.
On a side note, the '78 Tiger is a very rare & most desirable machine. Pretty much has the best of everything with the simplicity of the single carb. Those bikes are gems!
Don
My 650 Triumph limited duration race bike has far more HP and torque at the rear wheel than most Triumphs have at the crankshaft... It has six Taiwan clutch plates , T140 springs and running in about 8 ounces of ATF ....It does not slip...
If you read the original post it wasn't Mobil1 20w-50, but Mobil1 V-Twin 20w-50. They are very different products. The V-Twin is rated JASO MA2 and is designed to be used with wet clutches.
The 7th plate makes a big difference in the amount of torque your clutch can handle.
The amount of torque a clutch (T) can handle is based upon:
- The coefficient of Friction (COF) of the material used for the clutch facing (and whether it is used wet or dry, and as importantly the type of oil used - Modern "Energy Star" oil reduces the COF dramatically).
- Clamping force of the springs (Using the wrong springs is a common problem).
- Mean effective Radius (MER). It is calculated by outer diameter (d1) less inner diameter (d2)/2 or (d1-d2)/2
- Number of friction surfaces (each plate in a Triumph plate has 2).
T = COF x Clamping Force x MER x number of friction surfaces.
Reduce any one of the factors and the clutch will be more apt to slip. Increase any of the factors and the clutch will handle more torque.
Increase the COF by using the clutch dry (impractical on a Triumph with a chain drive)
Increase the clamping Force with heavier springs (Increases clutch pull and chances cable will break)
Increase the MER of the friction material by using a narrower (larger inner diameter d2) limited by the ability of the friction material to handle heat
Increase the number of friction surfaces (a 7 plate kit adds 2)
But to the point on this slipping 7 plate clutch are you using modern automotive oil in the engine, and thus the primary???? You could add springs to the point where you would have trouble pulling in the clutch or a couple of more plates and the chances are the clutch will slip anyway.
johntioc, sorry for the confusion. I was referencing TR7RVMan's suggestion of trying Mobil1 V-Twin 20w-50, but left out the V-Twin. Just to make sure we're on the same page, the full name is Mobil1 V-Twin 20W-50 4 Cycle Motorcycle Oil, and it's a full synthetic.
I have never used automotive oil in the bike. As I mentioned earlier in this post, I am using Valvoline 4-stroke motorcycle Conventional 20W-50 Motor Oil. The literature states that it is designed to be used with wet clutch motorcycles.
Great! Some people are still not up to speed with the problems modern automotive oil cause with wet clutches. Just wanted to be sure - better to check than be sorry...
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