Modern Vespa

Is the woodruff key the only thing that stops the clutch from spinning on the crank?

The crank on the flywheel side has a taper and I understand that the torque of the flywheel onto the taper of the crankshaft is what keeps the flywheel from spinning on the crank. But on the clutch side there is no taper. My clutch came loose on the crank a while back and now the key is a little loose in the slot. It's now ok but whenever I ride I'm paranoid that the clutch is coming loose again, and with a 1000km ride coming up I want to be somewhat sure it will make the distance.

Any thoughts would be appreciated.

Cheers

with it being loose it could have slammed the key,maybe?
A 1000 mile trip would be reason enough to put new key in.
Then again the key thats in might be the strongest key you'll ever have.50/50
Have fun on trip!

Yeah, The key is fine but the slot in the crank has been widened a little from it being loose before. I'm hoping someone has a trick for keeping the clutch tight on the crank when this happens.

Are you sure the slot us enlarged? The woodruff key is softer metal than the crank shaft in order to keep that from happening. Sounds like you may have a fly side key in the clutch side. I think the clutch side is 4mm and the fly side is 3mm... I think.

There's a big difference between them, it would be very difficult to mix them up.
I wonder if you could have the keyway welded and re-cut? Though it'd be coming close to the price of a new crank I imagine. The other thing that you might do is JB weld it in place, that stuff sticks like shit to a blanket.

I assume the 1000k's is the Mille?

Thanks all. I do have the right key in there.

I've just come back in from the shed after taking the clutch cover off to check. It's still tight on the shaft and hasn't moved since last time I checked it. I just need to trust it will stay put I suppose. But I know it not 100% right so it bugs me.

Yes ginch, it's the mille. Looking forward to it but nervous at the same time. The first day should be ok but the second seems like an f'n long way.

I think he's made a little mistake because the route doubles back just after Goulburn and then turns around and goes back along the same road... I worked it out without the little loop and it's about 520 all up. Much easier!
Four or five of us are riding up from Melbourne so we'll be seasoned professionals by then. Assuming of course that we make it!

Hello

Three different types of nut on the clutch over the years the castellated nut and tab should never come loose, the large nut and grover washer sometimes and the flanged nut all the time.

Grumpy

Thanks Grumpy. I always watch out for your posts as they always contain pearls of wisdom. I have the castellated nut and tab washer and probably didn't torque it right or use the tab washer correctly the first time. Is the torque really important here? It seems like the woodruff key is doing all the work.

Ginch- you'll have calluses on your arse by the time your finished. Crazy stuff. How many days you taking on the way up?

Hello

The Correct Torque is your friend here,the clutch has to be a stiff (solid attachment) part of the transmission and any movement on the shaft can cause chatter of the parts and will in extreme cases break the woodruff key, if you are happy that the key is good and you have the correct torque, tab washer is in place.

Have a good ride

If you are worried take a spare key and you will not be worried.

Grumpy

Sounds like cheap insurance of the best kind. I'll add it to my spares list and the clutch nut tool to my tool bag. Cheers.

Does the key fall out of the slot easily without the clutch on?

We are going to ride up over three days, avoiding the big straight roads where possible and diverting for the nice twisty ones. Hoping there will be enough time up our sleeves to attend to any issues on the way up and won't break down on the event itself. That's the theory anyway... I only put my new motor together last weekend...

Yeah it's not tight. I remember if I rotated the crank so the slot faces down it would have dropped down into the case. I used thread locker last time I put the nut on and it seems to be holding well so I think I'll leave it be. You know what they say.....if it ain't broke.....

See you at the start line.

Normal in my experience.

When I was a kid an old guy told me they just floated in there ,when it fell out and lost it I told him Glad they didn't just fly in there.haha which it did,flew out of sight.

Funny until it flies into the case.

I was just putiing a clutch in a motor Today, and I'd stuck a little rag in the gap because I don't ever want the key to fall in, and it DID fall out (I was actually picking it out), and I could have sworn that it went inbetween the rag and the primary... I said the F word about 75 times... I was just about to pick up the motor and see if I could miraculously dump it out, and id not I was ready to open the damn case, and out of the corner of my eye I saw it behind one of the legs of the table.... I did not want to do that... Most of mine fit kinda snuggly into the keway usually.. depends on where I get the key.. they're not all cut the same... I've had to file several too.

I've ridden 10k miles without a clutch side key, it's not what holds the clutch in place.

Hello

What does hold it in place?

Grumpy

Huh?

Thanks for bringing it back to my original question but please explain further. Very interested in a technical explanation.

Yah, I'm the edge of my seat. I want to hear this explanation.

When I first got my vespa I rebuilt the clutch and didn't retighten the nut properly, resulting in a sheared key.

Not having another one on hand I just tightened the nut properly and it held fine.

I ended up blowing that clutch and got a used one from a friend. I've also replaced my crank since then. Each time I never bothered getting another woodruff key, and I've never had a slipping clutch since that one time.

I guess the friction at the points where the clutch and crank meet is enough to stop the slipping. It makes sense to me because there's no way the woodruff key is going to transmit that power.

I just don't know why there even is a key on that side. The flywheel needs one for ignition timing, but the clutch?

I wouldn't recommend not using one,there not there for shits n giggles

Thanks for that. I'm surprised it holds but good to know.

I think they are. D'Ascanio knew how many would fall into the gearbox. He's still laughing in his grave.

He was a smart man.