Modern Vespa

First test rides today after a rebuild with BGM 177 kit, BGM 57 crank and BGM Superstong clutch. Clutch is behaving strangely.

Clutch behaved ok in the workshop rolling it around in gear. A bit heavy but no issues. Selected first ok with the motor running.

First ride started out ok, but I didn't get far before the lever developed a load of slack so the clutch wouldn't disengage anymore. No idea where the 5 to 10mm of slack came from, the trunnion hadn't slipped, and it hasn't gone slack again since.

Second ride after readjusting. When stopped in gear with the clutch pulled in it's initially ok then after a few seconds it starts to creep, feels like you're releasing the clutch when you aren't, after maybe 8 seconds you're either pulling away or stalling depending on what you do with the throttle. The next couple of gear changes are tricky but the clutch bite seems to return to normal after that, then the pattern repeats the next time you stop.

Returning to the workshop with a warm motor and again trying to roll it around in gear with the clutch pulled and it'll roll forward with just very minor clutch drag but it won't roll backwards without turning the motor over - not normally something I'd test for but it stood out as odd.

The original oil pump drive gear is fitted behind the clutch. The 4 parts in the release mechanism are new, the brass plunger, steel plate, spring and little lever arm. The clutch is new and was bought as a complete assembly, I haven't had it apart. The nut was done to the correct torque.

It'll be a week before I'm able to work on it again, but it'd be good to have some troubleshooting suggestions lined up ready.

Sounds like the cable or clutch arm are binding. The clutch arm should have minimal resistance other than the return spring by itself.

The cable may have broken a strand which is now hanging inside the outer.

Maybe both.

You may have also caused accelerated wear of the pressure plate and top hat, so check those while you're at it. Those can completely wear out in a couple miles if the clutch isn't releasing cleanly.

Thanks. Gives me a couple of things to go at when I'm back home.
Thinking about it there is a coarseness to it at the lever that might also indicate a broken stand or a cable rubbing somewhere.

I've just reassembled it after removing the cable and the clutch and checking everything. It's now much lighter and seems to be working ok in the garden but a test ride at the weekend will confirm it. I didn't find much, the clutch cable outer was 2 1/2" too long, and the clutch release arm had been rubbing on the clutch.

the arm rubbing is a new one to me, but it could certainly produce the symptoms you were experiencing, I think.

Glad you maybe have it sorted. Let us know how the weekend test ride goes.

I found it odd that edge which was rubbing is the one that rotates away from the clutch when it's operated. I still haven't got my head around how it could give the symptoms I was getting but I couldn't find anything else wrong.

seems strange, I agree, but if everything else is better, it may be that you inadvertently fixed the problem when checking/cleaning everything else.

Went for a test ride today and the clutch was spot on.
Time to move onto refining the jetting.