Modern Vespa

Hi,

First post here - welcome!

I have a 2005 ET-4 with about 12k miles on the clock - originally bought it new in NYC when I was "courting" and that was so long ago that her son is now the daily rider

So he was riding into school this morning and about 5 miles after setting off called to say the Vespa had broken down. Being wise beyond his years he waiting to spill the gory details till his Mom was off the phone - basically the rear wheel locked up while he was riding, he went onto a skid and was amazingly lucky not to have a gravel breakfast. He said the bike had stalled, had taken a while to get restarted but still "didn't sound right" By the time I got to it the engine is running fine and sounds ok at all revs with the slight problem that there is no power transfer to the rear wheel at any engine speed.

Any ideas on what might cause that sudden and total a transmission failure? I've read a bunch of other posts talking about variator nut failures, I really don't have any idea on how the CVT drive works or what the key components are, can anyone point me to some general wisdom in that regard? Thanks!

Probably a broken belt. For starters, open up the CVT cover…

Not very likely the nut worked itself off unless you've been in there recently. I'll 2nd the vote for a shredded belt.

As original owner, was belt ever changed?

OK Thanks to everyone for pointing me towards belt failure, and also to scooterwest for the belt replacement kit.

Yes the belt has previously been changed but I confess that was 6,000 miles/15 years ago!

Over the weekend I pulled the belt cover and lo and behold the belt was shredded. Remnants of rubber and fiber everywhere including wrapped around the inside of the clutch. I cleaned it all out, removed the clutch and the outer and variator drive pulleys, and replaced the rollers and guide tabs in the variator pulley. Even though I replaced them, I noted that the existing rollers were dirty but smooth; there were matching circular bands of discoloration on both the variator and outer drive pulleys, but no significant grooving; I cleaned the discoloration off both halves, sanded out the minor grooving with 120 grit paper and cleaned everything thoroughly with brake parts cleaner. The boss in the variator pulley was clean and shiny, all bearings rotated smoothly and I put touches of grease on all these. I installed a new OEM belt, torqued the variator nut to 61 ft# and the clutch nut to 45 as per the scooterwest video...Everything went back together smoothly and hopes were high...

Until I fired her up and the variator/clutch aren't operating correctly. As I increase engine speed the clutch begins to engage but I lose power as I continue to engage the throttle. At full throttle, the transmission and rear wheel cycles through high speed to low/really struggling/stalling back to high speed, about a 3 second cycle time. Any load on the rear wheel and the bike stalls. The engine idles and throttles up fine with no load (I tested with the belt and clutch removed).

I'd suspect clutch damage as the cause but when I removed and inspected the clutch, its action felt smooth with consistent spring resistance, no grinding, catching or excessive play (pressing down on plate and twisting at 45 degrees). The inner shaft looked clean and free of any belt debris. All bearings appeared smooth with no grease leakage. The inner clutch plate surfaces had some minor corrosion close to the rim but no grooving and were smooth and clean other than at the extreme outer circumference.

Any ideas?? Thanks!

How far did you strip down the clutch/driven pulley. Possible there is still belt debris jamming things up?

bluecloud - I didn't disassemble the clutch and driven pulleys yet, simply manually checked the contra spring operation and visually inspected what I could see when spring was compressed. Am considering taking it apart but weighing up the cost of the spring compression tool and the complexity/risk vs reward of completely breaking the clutch down vs simply buying a new clutch/pulley setup for $170. I know there are youtubes of people compressing the spring with their feet while removing the large nut, I'm a little concerned at what might happen to my similarly sized but softer nuts if my foot were to slip

Just stand on it and tighten the nuts by hand a couple of turns. Then finish tightening them with a wrench. Done. I managed to do it on the first try.

And Robot has a video on how to do it without a compression tool (his feet).

i changed the spring on my lx50 without any special tools

see my post for the details. scroll through to the relevant bits

LX50 -> LX80 RMS Big Bore Kit (Post 2713112)