LM3 clutch issue

[wirespokes]

This is a 'new' bike I've been sorting out. Took it on the maiden voyage and I'm really loving it.

However... it's got this weird clutch issue. Started out with shifting problems so looked into the cable adjustment - which was way off. Couldn't adjust the adjuster because the jam nut had been jammed on so tightly at some time the threads were buggered. Pulled the arm, removed the adjuster and eventually got the nut off. My tap/die kit doesn't have an M10x1 die (evidently not a common thread pitch) so 20 minutes later with a thread file had the nut threading easily.

It's shifting much better now, but it still has this weird problem. With the clutch pulled in, trans in gear, there's some resistance spinning the rear wheel in the forward direction. But that's not the weird part. What's weird is I can barely move the rear wheel in the reverse direction.

The bike has 18K on the clock, and looks it, with no record of the clutch having been replaced. I guess that doesn't rule out the possibility since there was so much trouble with clutches in the 80s.

Any ideas what could cause this weird behavior? I'd think that if the clutch disengages the transmission, it should be the same either direction.

[LesP]

I was curious enough to check the Eldorado.
With the clutch lever in and in any gear the back wheel spun either way the same (pretty easy)
About all that happened was the gear box sped up depending on the gear selected but you could hear things rotating on the gearbox for sure.
I even backed the cable off to very little hand lever, it went from locked wheel to plates just scraping then smooth free wheeling (It is all new parts though)

What happen's when you adjust the clutch cable for no free play at all ?

#
Turning the gearbox backwards can load the helical gears (and dogs) differently so there could be drag from that (shimming or engagement)

[guzzisteve]

I swapped out my stock one on my LM3 at 15K, it still has the short splines but it's been 35K this time. I use the sintered bronze plates. Was the hot set-up at the time but it does groove the pressure plate & ring gear.
I think yours is notched hub.

[moto-uno]

 ^ +1 , with guzzisteve . In not too much time you'll find you can only get into neutral when it's still rolling and then
the engagement becomes really grabby . Rust on the hub and clutch plate debris in the flywheel splines on so on .
It's a pain , but cleaned up with a new 4mm spline and plates and you'll probably never go in again . And what better
time than now :)   Peter

[wirespokes]

Les - like you, I spun the wheels on the 85 and 87 LM4 and they spun easily either direction.

Good idea removing all free play and see what happens.

Another factor, though I don't think it had any affect on the current situation, was the clutch arm return spring was missing.

Now that I've got the clutch adjusted and the shift lever positioned in a good spot I have no trouble getting all the gears or neutral. So I don't think the splines are an issue. I did pull the shift lever and the plastic bushing was a little worn where it rides on the bolt threads. Turned it around to the other side, plus I removed that coiled flat spring that's supposed to keep tension on the arm. Removing it gave a little more bolt shoulder for the bushing to ride on, rather than threads.

On the other hand, perhaps there is a problem with the splines if the clutch isn't totally disengaging.

Releasing the clutch should disconnect the transmission, so that shouldn't be coming into play. But since the clutch isn't completely releasing, that might be the case. So why would it be an issue in 'forward' but not 'reverse'?

Something I thought of: With the clutch arm spring missing, the throw-out rod could have been wearing into the spring. But, no - the clutch works and there's plenty of adjustment left.

The rear wheel rolls freely both directions in neutral. So it's not the final drive or wheel or brakes. And in neutral, everything through to the trans output shaft is connected. What a weird problem!

[jwinwi]

Clutch friction plates are worn too thin? Possibly a result of the missing clutch arm spring?

[Antietam Classic Cycle]

Clutch plate rivets sheared, friction material loose and jamming.

[wirespokes]

Clutch plate rivets sheared, friction material loose and jamming.

Sounds possible. What could be the explanation for dragging in reverse but not forward?

I am beginning to think a crabbing is in my future. So far, every one of my 3 Guzzis has, for different reasons, needed clutch work. T3 - grabby SureFlex. 87 LM4 - notchy splines. 85 LM, rusty pressure plate. And now this one... I must be a magnet for clutch issues. 

Woulda been nice if my friend, the PO, had warned me of some of these issues, like rear brake not working, no air filters, tank repaired poorly, no battery, no mirrors. And now the clutch.

At least I'm getting faster at fixing these things! 

[Groover]

Sounds possible. What could be the explanation for dragging in reverse but not forward?

Probably some weird feathering (like tires) with to the clutch sections allowing it to slide one direction (normal direction) then catch on reverse direction. Just a guess.

[wirespokes]

I'm leaning towards Charlie's suggestion of clutch rivets coming loose. Makes the most sense. I'll have to rummage through my spare parts and figure out what needs to be ordered. I don't think I've got any 2mm clutch discs left, so will need to upgrade to the 4mm. I know I've got one 4mm disc, but might possibly have another. I'll need a hub. So the order will most likely be for a disc, hub and intermediate plate.

Probably best not running the bike till it's fixed. I had been thinking of running it with the possibility of it freeing up, but now don't think that's wise. What's it like when a disc comes apart? Anyone had this happen? Does it trash any other parts?

Is it possible to determine whether this is the case or not peering through the timing hole? Would the clutch discs be visible?

[Antietam Classic Cycle]

I'm leaning towards Charlie's suggestion of clutch rivets coming loose. Makes the most sense. I'll have to rummage through my spare parts and figure out what needs to be ordered. I don't think I've got any 2mm clutch discs left, so will need to upgrade to the 4mm. I know I've got one 4mm disc, but might possibly have another. I'll need a hub. So the order will most likely be for a disc, hub and intermediate plate.

Probably best not running the bike till it's fixed. I had been thinking of running it with the possibility of it freeing up, but now don't think that's wise. What's it like when a disc comes apart? Anyone had this happen? Does it trash any other parts?

Is it possible to determine whether this is the case or not peering through the timing hole? Would the clutch discs be visible?

Depending on how hard the rivets are/were, they can gouge the pressure plate, intermediate plate and ring gear. Usually if they've failed, they pretty soft and don't do any damage.

Nothing helpful really in view through the timing hole or even the starter hole really.

[PeteS]

Every time I post this the gurus groan but its kept me from having to remove the trans to fix the splines.
Remove the timing plug, tighten the clutch cable for minimum play and then use WD40 aimed at he back center of the clutch area to drown the splines while working the clutch. Do it for about 10-15 seconds. Make sure you are doing this on a gravel or with lots of newspapers under the transmission. The WD40 will burn off the friction area in a few hundred feet. If I do this is the spring the clutch will be free until I put it up in the winter.
Obviously won't fix the plates coming apart but won't do any damage.
If you try this, duct tape the WD40 tube to the can or the ring gear will catch it into the bell housing.

Pete

[moto-uno]

  ^  A few decades ago I wish that remark about taping the tube to the can had been made . When winterizing my Le Mans 2
 I was soaking everything in  wd-40 ( it really kept rust at bay ) and the last cylinder to get blasted , also got the tube :( .
 Geez was that an idiot moment . And yep , I took the top end off to remove it .
   A fellow I knew some time ago would seal off the clutch housing on his old boxer BMW and half fill the clutch housing with
mineral spirits while having the clutch pulled in and spinning the rear wheel ( in gear) . I t worked for him for a number of
years before he'd go into it for a proper repair . When you have little to lose , why not ?   Peter

[wirespokes]

Thanks guys.

I dug around and found several good 2mm clutch discs, so should be good to go. The bike will be parked for a while till I can get around to it.

[wirespokes]

Crabbing today produced some munched clutch parts. The problem wasn't a disintegrating clutch plate. There was a fair amount of rust in there, which I'm guessing accelerated spline wear - clutch disc hubs, flywheel and trans input hub are toast.

It's sad having almost new discs (7.9mm thick) with worn splines.

Anyone have a good flywheel suitable for an 84 LM?

[moto-uno]

  Quite a while ago when finally replacing a clutch pack on my Le Mans 2 I found the the flywheel splines to be quite
notched and thought of a new flywheel, but because I'd had it lightened , I asked a machinist that did much work for
the custom shop I worked at if a repair was possible . He made a tool which basically pushed through the notched
side of the splines ( I don't know how many at a time). They were a bit thinner , but perfectly smooth and I still have
that flywheel in it 2 decades later . I remember he charged me $100 at the time .  Peter

[wirespokes]

I was wondering about that Peter. The wear can't be more than .010", so smoothing shouldn't make the teeth enough smaller to make much of a difference. How many miles have you put on it since then?

[moto-uno]

  At least 100k kilometers and it was still easy to find neutral and it didn't slip .
However about 3 years ago I went in for a mainshaft input seal leak and updated
the hub to the new 4mm unit and clutch plate kit from MG cycle . I think it was the
SD-Tec kit . The flywheel still looked fine .   Peter

[Chuck in Indiana]

He made a tool which basically pushed through the notched
side of the splines ( I don't know how many at a time).

That was a broach. Most likely one at a time with a rotary table.

[moto-uno]

  That sounds correct , thanks for posting that !  Peter

[wirespokes]

I asked my machinist friend to make me a broach to fix the flywheel teeth. After he explained the process, I could see there was no way that was gonna happen. Harpers didn't have one (the LM3 is lighter than most of them, so a bit unique and scarce), so used was rather remote. Besides, the cost, getting a flywheel from europe could take a while.  Since it looked like new flywheel time, I figured there was nothing to loose, trying to make this one usable.

It was a long painstaking process cleaning up those teeth - all 66 of them. I'd spent almost as much time cleaning up the ways on my lathe, so I've had practice - but I'd evidently forgotten what a drag it is. Fixing the ways involves a practice called scraping. It's one sharp edge scraping along the cast iron something like a one-tooth file. I took a thin file and ground the end a little under square and sat peering at that flywheel for hours carefully scraping each individual tooth. Got it done over a period of a couple days.

The teeth aren't perfect, though they are much much better, and the ridges are gone. The wear was around .010" with the unworn area about a third of the middle of the tooth. Only one side of the teeth were worn.

The big question was whether the clutch would function properly. Thinking back, with it as awful as it was, the clutch action wasn't bad before, even with the heavy flywheel and clutch hub wear. The teeth on the clutch disc centers were worn quite badly, so they probably weren't hanging up at all. But there was a lot of debris in the splines.

Now I've put on 50 or 75 miles and the clutch works perfectly. I guess I'll start watching for a good used flywheel and have it lightened, for some future time it might be needed.