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Hi all,

I hadn't investigated the primary/clutch area on my '68 Bonnie yet, however the clutch has been dragging and I wanted to get round to tackling it.

When I drained the primary it seemed very low on oil. Removing the cover the primary chain looks okay to me, as does the tensioner, though I've not taken these out.

My main issue is the clutch and basket. Removing the clutch plates, the friction plates were sticky with gunky oil. One of them looks worn but I'm guessing they're all scrap. I wanted to ask about the metal plates though as these show no obvious wear - is there anything I need to check for (warping or anything like that?). Trying to decide if I need only friction plates.

The clutch basket has me worried though. Looking at the slots the clutch moves in I see what look like notches (see photo). Is this normal/acceptable or some weird wear pattern? The inner slots that the other half of the clutch connects to look fine and show only minimal pitting.

There was a little sludgy oil in the bottom of the primary casing, and testing it with a magnet it shoes some metal content. It's not going to be particularly easy to clean out and I'm guessing some parts of the alternator as magnetic. Should I be removing everything in the primary and cleaning it up or is this overkill?
 

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When you say it's dragging, what exactly do you mean? Trying to creep forward at stops? Mine always sticks when started, in fact the owner's manual explicitly says to free the clutch prior to starting the bike.

Anyway, you might as well replace the friction plates, they are cheap. The manual says to check the steel plates for flatness on a sheet of glass. I also checked mine for wear with a micrometer, but I am still using the originals.

I am constantly surprised by how little oil is in the primary case. It's just enough for the chain to skim through it on the bottom run.

That clutch basket would concern me, though. I thought the manual discussed this, but I can't seem to find it now. The plates have hammered the edges of the basket, they should be straight and flat so that the tabs can slide freely. Mine have a few dings but nothing like that. Having never seen one like that, I don't know how much a problem that is. I would assume that would prevent the plates from separating freely - I am betting the distance between the centers of those divots is the thickness of the steel plate plus one friction plate.
 

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Can you tell what the state of the clutch shock absorber rubbers are? They are there to prevent this - without them lash in the drivetrain would act like a hammer.

DON'T try and take the rubbers out to inspect them. Unlike the description in the manual which treats this like a casual feat, they actually are a royal pain to reinstall. You wouldn't want to take them out until you are ready to deal with it. By hand there should be no real free play in the clutch central hub.
 

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Definitely time for a new Clutch Hub/Drum. You might be able to file the slots and make them straight. However, if all the Tabs don't make contact simultaneously with the Clutch Hub/drum, new divots will be generated quite rapidly. As has been suggested the clutch shock absorber rubbers might be in need of replacement as well. At the least the hub that encloses them may well be packed with crud in such a way as to render the rubbers ineffective. One last minor thought; when all is repaired be sure that the drive chain is adjusted with sufficient slack so as to minimize drive-line shock from the wheel back through the drive-train.
 

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That part is scrap metal,but as said,check the grooves of the centre and i would replace the rubbers if they have been in use much over 3 years.Plates are often good to re-use with a good clean.Lightly roughen the plain plates with just a little rubbing with abrasive paper.Not all over until its dull,just a light rubbing.
I would check you have alternator clearance at this point with the cover off.
Check the primary chain for wear and missing rollers.
The rubbers can be fitted easier if you put them in boiling water.Use your own clutch centre with a long piece of bar bolted to it as a tool to squeeze them up when you get to the last 2 rubbers.Sometimes you might buy rubbers and they are a little slack so not requiring this long lever.Most important is to make sure those centre screws are very tight on re-assembly as they can undo in use.
 

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Discussion Starter #6
Okay, thanks all. I'm amazed at how much damage there is to the clutch basket. I've not had the bike long so I don't know the history of the rubbers. Are these mounted on the inside of the clutch hub?

When I say the clutch is dragging, even with adjustment done on the cable I noticed two things : first if I try to kick the bike through with the clutch pulled it would take a couple of kicks to get the clutch to unstick. Secondly if I'm riding the bike the clutch seems to work okay on upshifts, but when stationary I get a significant gear grinding sound (sometimes) going into first, and also (sometimes) going down from third into second. It wouldn't surprise me if at least part of the clutch was sticking together or not running linearly along the slots.
 

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Okay, thanks all. I'm amazed at how much damage there is to the clutch basket. I've not had the bike long so I don't know the history of the rubbers.
I have replaced mine several times looking like that in under 12,000 miles.
There has to be a better material to make those things out of.
 

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I keep a couple of old clutch drums to use rather than buying new,dubious quality replacement new ones.
Yes,the rubbers are in the centre part of the clutch and there are 6 of them.
It is not often the roller bearings and thrust washer wear out but check them.
With those notches,it would be difficult to change gear as some plates might even stay a bit locked up having to pull up the ramp of the notch.
With a well adjusted clutch and good gear set,there will be virtually no noise as first gear is selected.On mine you just hear the click of the lever mechanism.I also have very easy neutral selection.
When i got this bike it had a terrible dragging clutch and i did have to replace most of it.
 

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When I say the clutch is dragging, even with adjustment done on the cable I noticed two things : first if I try to kick the bike through with the clutch pulled it would take a couple of kicks to get the clutch to unstick. Secondly if I'm riding the bike the clutch seems to work okay on upshifts, but when stationary I get a significant gear grinding sound (sometimes) going into first, and also (sometimes) going down from third into second. It wouldn't surprise me if at least part of the clutch was sticking together or not running linearly along the slots.
Well, the kicking thing is pretty common. Like I said, the original owner's manual explicitly says to kick the clutch free prior to starting. Since you start these bikes in neutral, it's possible to start the bike with the clutch stuck, and if the clutch hasn't been freed and you try to make that first shift it will hammer the thing pretty badly. It should free after a couple kicks.

On mine I do have to be a little careful about what speed I shift into first from second - it bounces off if the bike is still moving too quickly. OTOH, the 500 is a little different.

I have a vintage Yamaha that has swollen friction plates. The dragging is really obvious. In particular, when shifting into first from neutral there's a big clunk and the engine slows down. The engine design makes swapping them a lot harder than on the Triumph.
 

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Hi Scott, Where are you in California?

Regarding your clutch, I have a lot of experience with them. I've seen this wear before & know exactly how it feels & how it acts when it's worn. There is a lot to this job. Nothing really hard, but you must do the whole job or it won't work properly.

Thanks for the photo, that really helps.

As you suspect the plates tend to catch on the ridges which prevents them from separating smoothly. Also it often prevents the plates coming together smoothly as well. I've experienced some that occasionally a plate would actually hang up on ridge & clutch would slip & lever would have way too much play until plate found its way back. Very odd the things it can do & can be hard to diagnose without visual inspection.

Primary oil is extremely important for good clutch operation as well.

I don't know what causes this wear, but my hunch is not changing the primary oil especially if condensation builds up. Also high mileage will do this. I don't see rust, so condensation may not be a factor in this case. I've seen several chain wheel (baskets) with 20k miles on them with a fraction of that wear. I've wondered about oil types/brands that may reduce wear. I feel oil drag on plates accelerates wear, but I really don't know.

With this much wear I would not attempt to refinish grooves as they are then way too wide.

I only see the very edge of inner drum, but I expect it will have excessive grooving as well.

Most certainly the tangs on plates will have wear/damage as well. I expect inner plate tang damage also.

Primary chain will have to be removed & measured per the shop manual. The max is 1/4" as I recall. That's way to much wear for my comfort. I like to change at 3/16" stretch tops. I current have a primary apart. About 20k on bike. That chain has 1/16-3/32 stretch. Will reuse it.

Regarding chain wear, the sprockets wear to match the chain. If you use new sprocket with worn chain it tends to rapidly wear sprocket to match chain wear. Front sprocket needs to be checked for wear too. Clear close photos of front teeth would help. But if chain measures good & front sprocket looks good, reuse them.

It would be wise to replace front sprocket seal also. Remember spring in seal goes towards sprocket. That is a fact. Don't reveres it.

Regarding the tensioner, it is normal for them to groove where side plates run. Once rollers contact rubber the wear pretty much stops. Look for cracks, splits, little chunks of rubber coming off. That's bad. If rubber has come loose from tin, that's bad. Take out adjuster rod & examine threads, nut threads, end of rod for wear/damage. The head can wear & pull through sometimes. Get a hex head primary chain adjuster tool & snap-on 1/4 drive 7/16 universal socket. It will fit nicely with long extension. Makes chain adjustment very easy.

At this point you need to do full tear down. You'll need clutch hub puller, crank sprocket puller, torque wrench, chain adjuster tool. Plus the home made clutch locking plates & the clutch plate with a long handle bolted to it. Worn tangs are not a problem for these tools.

DO NOT mess around jury rigging the clutch hub puller. Just get one. DO NOT guess on torque of main shaft & alternator nuts!!

You can use automotive vibration damper puller for crank sprocket as they work fine. Harbor Freight sells a cheapo one that works. You may need to buy separate puller bolts. 1968 will have SAE bolts, but watch out for CEI thread bolts. Don't mess up on this. The clutch hub puller needs to match threads. If you don't have thread gauge you need one.

It may be possible to pull chain wheel separately, but don't count on it. Also I would not be surprised to see hub bearing race wear/damage. Watch the Lunmad youtube video on how he does clutch rubbers. It will show you how he does it. I pull crank sprocket & clutch hub simultaneously.

Look at the race in chain wheel & the rollers, race on hub.

You will need new chain wheel. It may or may not come with race. You'll need new thrust washer behind chain wheel. Examine it carefully. There are a few versions & you need to get the correct one.

The clutch hub rubbers are almost certainly worn/deteriorated. The new inner drum may or may not come with them. If not you'll need new rubbers. If new drum doesn't come complete, you'll need to examine spider & side plates for wear/damage.

You'll need to make or buy clutch locking plates & a long handled holder plate to hold parts steady & to lever drum to remove/replace rubbers. I recommend making them. I have photos of all the stuff I made & the pullers etc. I posted them here some time ago, but can't seem to find them. PM me & I can email them to you.

I would do tear down & take the drum apart & remove rubbers. Then you'll know all the parts you'll need. This is going to cost you a some bucks... Just the way it is. Good used parts are fine if you can find them, that is if... Replace rubbers on any used drum.

You'll need all friction & steel plates. Regarding clutch plates, trust me on this, get a Hyde 7 plate set all new friction & steel. If your steel plates were perfect you could reuse them but any wear on tangs will very soon wear the new chain wheel & drum. If springs & pressure plate look good, reuse them. No advantage to use aftermarket aluminum plate. Check rod ends for wear, check adjuster bolt for wear. Hyde plates work really, really good. They just do. Free perfectly, 1 kick & no slip. Bonneville shop & others sells a different 7 plate kit. I've never used them. I've only used Hyde & know they work. Soak new friction plates overnight will oil.

At this time it may be a good idea to get a new clutch cable. I most strongly recommend only the Barnett cable. They are very strong & ends are swaged not soldered ends don't pull off. The friction is very low. Every bit as low as Venhill & much stronger. Easy to change on the '68.

Clutch oil is most important. The 1968 allows you to use any oil you like. After getting involved in several of these clutches I recommend Mobil1 v-twin 20-50 oil in the clutch. ATF F works well to, but I feel v-twin gives smoother take off, with just as good release & no slip. V-twin has very high zinc & seems to reduce wear also. I like it in motor too, but that's another subject.

Regarding primary oil level, the '68 has a level check drain. You can sort of drain oil out the chain adjuster plug, but I bet you found it didn't drain all that well. It works well to siphon oil out filler plug using a 9" long 1/4" brass tube & clear rubber hose from Ace Hardware. Do it with motor well warmed. I siphon into baby bottle so I know how much came out. Then refill per manual & check with level check plug. I like to change engine & primary oil every thousand miles. Just makes all last longer & work good.

Before I forget, very important to keep alternator rotor inside stator while bike is apart to prevent it from loosing magnetism. Or use "keeper" bars on it.

If you are getting oil leaks at trans sprocket area from either trans oil or primary oil, it's a good time to change those seals while clutch is off. That's its own job. You'll need tool for removing sprocket nut.

Strongly recommend Loctite #243 the clutch nut, drum screws, alternator nut. Look close at lock tabs for nut(s). Make sure the tab is actually into the keyway. Often it just misses it so lock tab doesn't actually hold it.

If you have high miles the 3 ball cam can wear also. If worn you get low lift. That's another subject. Get the clutch done 1st & evaluate it. They tend to last good though.

I can confidently say if you follow all this, your clutch will be an absolute delight.

If you are close to me I can swing by & take a look.

Don
 

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I must say,many thousands of Triumph twins run perfectly well with standard 6 plate clutches and too many people are trying to improve on something that works really well.Hence in 40 years of T120 use,i have not found any need for an extra clutch plate.I get no sticking plates,no need to kick the engine over to free a clutch which does not stick,no condensation in the oil,no crunch as i put it in first gear.
If was repairing this clutch,i would fit standard cheap plates which have proven to be excellent.
At this stage,most of it is worn out so you will need to buy most of the parts.Usually the front engine sprocket is very robust and i have yet to replace mine after 40,000 plus miles.Do not buy a cheap primary chain.
This job is very easy to carry out with the specialised tools.It can easily be replaced leaving the engine sprocket in place but removing the stator studs.I suppose it looks daunting the first attempt but just take pictures of the parts as they are fitted and when taken apart so re-assembly is easier.Use the parts book if you need to check assembly order.
 

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I must say,many thousands of Triumph twins run perfectly well with standard 6 plate clutches and too many people are trying to improve on something that works really well.Hence in 40 years of T120 use,i have not found any need for an extra clutch plate.I get no sticking plates,no need to kick the engine over to free a clutch which does not stick,no condensation in the oil,no crunch as i put it in first gear.
If was repairing this clutch,i would fit standard cheap plates which have proven to be excellent.
I concur!
 

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Hi Guys, Do what ever you want for the plates. The Hyde plates just work better plus I think they wear the grooves less. Maybe because they have 2 more plates, or... is it Hyde drags less so has less sideways friction in grooves?

In any case oil is very important to good clutch operation. Very important!

Regarding chain wheel & drum groove wear. Here is the parts on the '69 Bonnie. This set has covered about 18,000 miles.

Minimal wear on grooves. Mobil1 v-twin oil in primary. Hyde plates. The bike is ridden on many longer rides. Usually 60-200 miles. Not slow poking, but ridden gently. No wheelies or burning rubber. Primary oil changed every 1000 miles.

You can see the shape of small Hyde friction pads on chain wheel. The pads are small & thin, but they grip & wear well. Free very easily. Also you can back off the springs a turn or so which gives less lever effort.

Regarding the front sprocket, I didn't say replace it. I said inspect it along with the chain. Reuse if good.

Here's the photos of '69 Bonnie clutch.
Don
 

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Hi,

When I drained the primary it seemed very low on oil.
Should I be removing everything in the primary
As the thread's progressed, I'm guessing you now know the answer ... :)

The alternator could have as little as 8 thou. between rotor and stator, and the rotor is magnetic, so it makes sense to look at both surfaces and ensure they're free from any debris.

With the stator removed, you can also check your engine didn't get the 'tuning' that was fashionable at one time, that joined primary and crankcase. It involved removing the drive-side crankshaft oil seal, drilling one or more small holes through the primary/crankcase 'wall' in about the four o'clock position behind the stator and fitting a breather in place of the primary filler. Then, years later, as 'standard' became fashionable, aftermarket primary breathers were discarded and crankshaft seals replaced ... but small holes in the crankcase missed ... :Darn

When you reassemble, 8 thou. minimum clearance between rotor and stator all the way 'round is both achievable and important.

Mobil1 v-twin oil in primary.
Note the OP's bike is a '68, which shouldn't need engine oil in the primary?

Hth.

Regards,
 

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I was also using ATF and stock plates in my clutch with no ill effects but have to agree, this clutch basket looks extraordinary.
Was it original part or aftermarket ?
What's a difference in price between stock and Hyde plates ?
 

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For 18,000 miles,that clutch does look very good.My own does last a fair time given its regular oil changes and checks.My bike is ridden very hard and often with a pillion so it does work hard.
 

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Hi Stuart, I'm quite aware the primary doesn't share engine oil. Done some experiments on different oils.

Was running Torco primary oil. Worked ok, about like the old straight 20w from the early 70s. No slip, didn't free all that well.

Then used ATF F O'reilly's auto parts house brand. It freed well, no slip, but tended to be jerky/grabby on take off.

From the good results with Mobil1 v-twin 20-50 with oil in frame bikes, decided to use it in the '69 Bonnie. It worked quite well. Frees as easy as ATF, yet smooth on take off, no slip. This is with either stock or 7 plate clutch.

Others in the club have experimented with the v-twin with good results.

My hunch is v-twin may give better wear for grooves & chain. Will take another 20k miles or so to see it that is the case.

On the other hand regarding ATF different brands of ATF F or Dexron for that matter can have a large effect on the jerking at take off. At work doing services on automatic transmissions. Merceds brand, Penzoil, Shell all worked good. This was from either Dexron III or ATF 134. We tried Chevron & Mobil. These proved very jerky/harsh durning shifts. Customers were very angry. Changing back to the known good ATF cured problems in only 5 miles.

Back to the bikes, V-twin oil is about the same price as the good ATF. So my reason is possible better wear.

Don
 

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Hi Guys, Do what ever you want for the plates.
Thanks for your permission.

And you have my permission to spend as much money on aftermarket plates that you feel you need to get get your clutch to "work better". I'll stick to just adjusting the clutch properly. It's worked on my bike since 1972.
 
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