Modern Vespa

Probably not, but I'm already done. Took less time than it would have taken to google it!

Here's the base gasket template

Dig it.

Quick issue. Maybe.

Trying to put the clutch back in and it doesn't seem to wanna go.
There's 2 keys for this one, BGM superstrong, and both look a bit smashed, should I replace them? And is there any trick to seating this guy? There's no channel for the second woodruff key that's on the crank, just one slot in the threaded area. How the frig does this go back on the crank?

It's sheared off. The oil pump gear notch is at the bottom of the pic. It needs to capture the key. The other have of the key is in your clutch.

Ahhhhh ok now I see that. Thanks Rob!
New key it is then! And that explains a lot

Yes - the two piece key... Rare and not widely available.

If you have a small jewelers file, a little clean up on the edge of the crank isn't a terrible idea. it's a little mushroomed at the key slot edges. Nice to have that clean no drag.

The key that is in the crank - aka one of the two keys - looks like it might be a poor fit. Maybe even has a shim in there with it? That would be the root cause reason for the shear if yes. You want the key to fit nicely snug left and right side. Any right to left movement will allow momentum and sheer forces to increase.

The BGM clutch shoulda come with a key that has a half moon shape on the back. I like to grind off just a few mm at the end, so I can rock it slightly when in the slot. This way, I can tilt the nose slightly down when installing the clutch - and then it rocks into place flat as the clutch slides on.

That only works if the slot is super clean and straight sided. I also dress the bottom edge of the key just a hair if needed to insert in a tight slot. I like to have slot and key super clean - not a spec of debris to mess up the snug clean fit.

Even with side car and extra HP, using the same clutch you have and beating it pretty hard, I've never sheered one.

Snug fit is the critical part - so worth waiting a day for the right key if you don't have. My $.02

Hate to say it, but my own opinion is that it's time for a new crank, key, and clutch center. Hopefully the oil pump cog is still 100%.

I've seen worse -but of course you might be right...
We will have differing opinions...

That said - before I did a bunch of ripping down - I think I'd do the clean up and quality fit key trick.

Like any part, each key maker has their own level of "grade A" quality.
Sometimes the things aren't flat and parallel at all!
You might error on buying a few keys from different suppliers - read BGM and SIP - from stateside supplier - and inspecting/ micrometering both to see what fits must snug. Just gently file away that mushrooming first...

Its failure mode - if it fails again - likely won't be catastrophic - meaning it may not get you home if it fails, but I don't think it will create anything more than a nuisance.

Agreed there. Might as well clean it up and install a new $5 key and see what happens. It's not like it's going to make the parts any worse if it shears again. $5 is way less than $200~ish (plus time and labor).

When this happens, the clutch nut wasn't tight enough. 80Nm and blue thread lock.

Oil pump cog is kosher. However it does not come off the crankshaft. Looks like when the key sheared it got mashed around the crank arm and fused in place. So now the end by the threads is a little thicker than original.

Alrighty. Crank is out, but not after having to remove a chunk of the Grade 1- perfect repair https://www.sip-scootershop.com/en/product/tool-crankshaft-sip-for-disassembly-for-clutch-side-kulu-for-vespa-125-vna-ts-150-vba-t4-160-gs-180-ss-rally-px80-200-pe-lusso-98-my-11-t5-cosa_38886000?usrc=Tools ….

What do you guys think about the end of the clutch taper? Could I sand the smeared mess off maybe? Or since the crank is out just replace it with a long stroke?
Would I need anything other than the long stroke crank?
Just a new crank put her in and go?

Also took a shot of the clutch carrier. Doesn't look too bad to me.

You can clean that up and run with it. It's not a taper fit on the crank side.

But if you feel like spending by all means, get a long stroke. You'll need some base and head gaskets (which you now can make yourself!) to adjust the squish.

True, except I don't think he can make 1-2mm aluminum gaskets on a cri-cut

Not with that attitude I can't!

Awesome. Emery cloth or something else? I've got zero experience with this particular problem

I already gave you my 2 cents on what i think.

One thing i would not do is mix n match brand new parts with knackered parts. Either band-aid both the old ones, or buy brand new ones of each. The choice to me is super easy since you already spent the time to remove the crank.

As for a long stroke crank, you can go that route. It will add the complexity of getting a correct squish, then spending the time to rejet the carb.

emery cloth will just round over the ridges. A hard file will cut the ridges off and make it flat.

Yours doesn't look bad I'd just hit the high spots with a file followed by some 320 grit and run it.

I've sheared the clutch woodruff on my super strong way worse than that and it's been fine for years since then.

Careful filing off too much. Function is more important than pretty.
Long stroke crank would be nice. To decide, how tight is the clutch inner on the crank? Should be minimal play. If it's gone baggy, then decision made.

Filed it down to the point where the oil gear slides on with just a touch of resistance. Clutch will be easier on and off now too lol.

About to reinstall the crank but struggling with the how to with the crank installer tool that comes with zero instructions.
Going YouTubing now.

Appreciated. Just not trying to spend half the cost of a new crank on tariffs. Fingers crossed push doesn't come to shove.

Which crank installer is that? Mine came with no instructions, but I didn't think it needed any.

I usually put the crank in the freezer overnight to shrink it down a smidge. Then heat up the bearings (without damaging any of the seals). It's easier to fit the crank doing it that way.

The SIP one. I got that part sorted now.

Flying right along now. Instead of waiting for my wife to go into the office to scan the base gasket I decided to try to cut that one. Nailed it first try!
Had to use my dremel and sand the clutch carrier, it wouldn't slide on at all at first, too much of the woodruff key smeared in there I guess. Two quick goes with the sanding bit and she slid on slowly.
Pulled out my clutch nut and have the torque values for all the nuts written on the baggies….

Why the F does my clutch nut say 23-27ft.lbs?
I see why I sheared the key now if that's what I set it at before… put that back on at 70nM. Flywheel at 63nM.
Honestly after cleaning up the clutch everything went back together super easily. Not a hitch in the giddyup.
Even the pressure test. First try. Not a leak to be seen. Been at 6psi for 45mins. (Walked away to make dinner).

So back into the frame she goes tomorrow.

Went back to check an hour an 45 mins later. Still at 6psi. Can't get better than that!

Working smarter today

Working fast also.
Looks like the motor is reassembled.
U need a Santa's helper for motor install.

Spoke way too soon. Dammit.
Kickstarter doesn't engage and the clutch arm doesn't move. Yay. Whole day wasted. There's the dang ol yin to yesterdays yang.

Welcome to the club

Agreed with Socalguy!

Most often missed parts when I am asked to "fix" an engine tbat wont turn over

1 kickstart Gear

2 woodruff keys

I post a picture of the gear in place - to force myself to put it in place. I think I went through a half dozen gaskets last build and that was at least 1 of not 2 of them…

On positive note: u have gaskets!

Clutch arm. May just be brass plunger alignment or damage from clutch coming loose?

I'd be tempted to push-start it rather than split the cases... 😁

Well it's a bit icy and cold here so I'm in no rush to get her outside to ride right now….

However. Opened the cases and found my problem.
For some ungodly reason ( I think I was just resting it until I was ready to put it in place) I put it on the end of the primary shaft. No wonder that wasn't working!

Clutch is back out. I noticed that in other videos the innards of the clutch should spin around in the carrier. Mine don't.
So gotta open that up and see what's happening in there.

Plunger moves fine. Gotta investigate tomorrow

Update, turns out I have a clutch tool already. When the clutch is compressed the inners spin, not super freely but I can move them around. There's a point where when uncompressing (decompressing?) that that stops though. It looks like maybe the ring isn't sitting properly? I'll take pics tomorrow. I'm in bed already.

Ok got a minute today and took apart the clutch completely. Here's the pics below.

I found nothing that looks amiss. Let me know if you see anything though. When I put it back together I gave it more oil.
Still getting the same issue, can't spin the innards of the clutch unless the tool is compressing the plates a bit. Clutch arm doesn't move when installed in the case.

With the clutch cover off, the arm moves fine. So the cover can be ruled out.
Did I miss something? Could it be the pressure plate? Doesn't seem defective but I dunno what else is going on.


Step by step disassembly below.

Clutch looks okay. It shouldn't spin in the compressor unless it's compressed so the plates are separated, so that's fine.

Are you running stiff springs? What's the HP of the motor? (I.e. do you need stuff springs?)