Modern Vespa

Hello,

I finished rebuilding my P125 motor and got everything together and running. The problem is the new VMC 10 spring clutch isn't engaging.

I assembled and installed it per instructions thanks to BajaRob, my kit didn't include instructions. I've adjusted and readjusted the cable several times without any luck.


I soaked the plates in 30 wt non detergent oil overnight before assembling, but that was a few months before installing it. Does it need to be torn apart and resoaked?

edit: I dremeled out the clutch cover for clearance also.

Any ideas?

Thanks

Is it engaged when the cover is off?

I'm not sure, I need to pull the motor to find out, which will be the next step.

This is a strange one-

it's running and i would assume you kicked it over to start, yet the clutch is not engaging?

Is there some play in the arm before the plunger touches the pressure plate or does the arm feel rigid?

The arm feels rigid with no play, and the lever pull feels normal.

No need to pull the motor to check what's doing in the clutch. Ass lifted, wheel off, and you can get at those three bolts on the cover no problem.

With my VMC 10 molle I had those same symptoms when, as it turned out, the pressure plate had come loose, but stayed wedged in there between the brass plunger and the clutch basket. Eventually the plates were separated enough that I coudn't kick it over.

I suspect there's more tolerance in the VMC's seating hole for the pressure plate. My solution was to make sure the clamping retainer clip thingy was really bent 90 degrees and and didn't allow for any play.

(Or are you running that fancy red bearing-based pressure plate?)

That's the problem! With the cover on and the cable not attached, the arm should move a little before making contact with the clutch. It could be the plunger being too long or your clutch cover needs a spacer to compensate.

Thank you very much for this, you saved me a few hours work. I wasn't aware you could work on the clutch without dropping the motor. I am running the red pressure plate that came with the clutch.

Thanks, I'll check that out.

My 1950 Harley FL was a walk in the park to build compared to this

Did you put the brass small cylinder that gets pushed by the clutch lever inside the clutch cover? Without the brass small cylinder the clutch will never engage but the clutch handle might feel like engaging. Even the whole mechanism will move and will look like is working but there will not be any engagement. That brass cylinder is very easy to pop out of place. You will need to put a little bit of lithium grease to keep in in place.

Did you mean this?

Yes I did install it. Today I'm digging into it to hopefully find the issue.

Post some pictures of what you find.

Pictures are always helpful with questions like these, because the answer may be obvious to us if we can see it, whereas you still don't know what you don't know yet.

When you assembled the clutch, did you spin-test it (with the clutch compressed after assembly, you should be able to spin the basket since the plates are separated), then have them engage and not spin when you release the tension on the clutch tool?

i.e. confirm the clutch is working as-intended so we can affirmatively rule that out while we're focusing on the plunger, lever, and pressure plate.

I'll take some pics when I get it out. I'm learning on the fly here. The bold highlighted statement above is on the money.

To remove the entire clutch, the engine needs pulled yes?

Nope, you can take the clutch out with the engine in the frame. It's a little less obnoxious when you take the rear hub and brakes and brake cover plate off, but it's still possible with all that installed.

Yep. First Vespa rebuild is always interesting. My first rebuild was a VBB, and it was definitely comical to a fault. It really honed my cold, burning hatred of the Haynes Manual, though.

While the techniques build on each other as you work through the various motor types (Pre-P largeframe, P largeframe, smallframe, wideframe, etc.), there's gotchas unique to each of them. And that's before we even get into tuning and just the annoyance of re-pro parts not always fitting right... So long as you don't drop the woodruff key into the crank case, it's harder than doing it on the bench, but completely do-able with the motor in the bike. You don't even need to disconnect the clutch cable, just let the cover hang.

(It'll be a LOT easier if you replaced the castle clutch nut with a modern flange nut. That's a must-do update on all my bikes. With that update, I've done a complete clutch swap in twenty minutes.)

Given that most of what we're diagnosing is about the lever engaging, I wouldn't even worry about pulling the clutch itself to start unless you want to go ahead and dive in. Let's get a look at some pictures and make sure the pressure plate, lever, and plunger are all correct first.

I remove just the rear tire and deal with the bruises from the hub studs.

I already switched the castle nut with a flange nut. I figured that one out on my own😄

I'm getting pretty proficient at splitting cases, as I've done that three times to "fix" issues that I caused.

You're learning fast!

I always tell people that if their clutch castle nut tool has wear marks on the tightening faces, they're using it wrong.

Here's some pics before I remove the clutch.

It looks like the brass plunger is wearing around the outer edges, but not in the center. Is that correct?

If so, then either the clutch cover is not on straight or the pressure plate is not properly seated into the clutch, as JVM suggested up at the top.

It looks the same as when I installed it.

Does the cover fit onto the casing without interference? Does it fit squarely onto the casing with good o-ring seal? Looks pretty tight with the MOLLE. Sometimes the inside of the cover needs some material relief to have clearance with the clutch basket. Not saying this is the problem just something to pay attention to. SIP sells modified covers for this although I've been successful doing it myself with a sanding drum on a Dremel. There are also spacers that can be purchased to raise the cover if necessary. Again not saying this is what you are running into just something to keep in mind with non stock builds. Had to use a spacer recently myself.

Yes I had to dremel the cover to fit, and it mounts flush

That's good for clarification the clutch does not slip?

Define "not engaging".

Let's get on the same page. Do you mean clutch is not engaging, OR do you mean that you cannot DISengage it w/ the handlebar lever or the clutch arm?

If it is not engaging, drain your oil and try just loosening the three cover bolts. If it now engages, your stack up is too tight holding clutch open, and you likely need a cover spacer as mentioned. Or something is fishy w/ your nonstock hi end clutch install...

Ditto.

Do you mean nothing happens when you pull the clutch lever in, or nothing happens when you let the clutch lever back out? If it is the latter, I would be looking at the gear selector box.

You engage the lever to disengage the clutch.

Sorry about the confusion. Nothing happened when I pulled the clutch lever in.

It's working properly now after taking it apart and inspecting everything. It must have been the plunger/pressure plate being askew. The clutch plates and springs were all in order.

Excellent sounds like you sorted something out. Looking forward to a 1st start report. Know you've had FUN figuring things out which is part of the process and good for the soul plus you'll be much more in touch with it when things need attention. it will be rewarding in ways the 1950 Harley isn't but that sounds pretty awesome too. I've been eyeing one of those VMC clutches ever since I had Peter rob Paul. Maybe Santa will make it happen for next year's riding season. These things are fun next phase will be jetting it's not done messing with your head. Keep the faith you're getting there.

Thank You hibbert, I'm learning more everyday.