Modern Vespa

Any comments/advice appreciated before I spend a fortune at the repair shop.

My 2009 GTS300 died on me yesterday. Was riding flat out at 80mph when revs dropped and when I pulled over it cut out. Restarted but with low power and dies again if I try to rev over about 3000rpm so limped home slowly. There is a knocking noise from either the bottom of the engine or behind the airbox - difficult to tell. No warning light at any time. Scoot was serviced a couple of months back with new belts rollers filter, fluids.

Any thoughts on what could be wrong? I am worried that the lack of warning light might mean nothing shows up on diagnostic tool and I can't afford to spend a fortune on mechanics looking for the problem.

Any help gratefully received

First thing to check is the spark plug lead.

knocking noise AND you rode home? sorry to say but that sounds like a not so good idea

What's done is done. Check your oi and coolant. The noise may have come from the CVT - take the cover off and have a look. Check the air filter while you are there to see if it's all there.

how many miles?

as mentioned above- check the oil, check the coolant see what's up there.

pop the bucket out and see if maybe something popped loose- ECU, HT lead, plug cap, evap or intake manifold is compromised.

pop the cover off and have a look see. maybe you got lucky and it's just a belt or clutch.

a repair shop should be able to determine fairly quickly if it's bad in a big ugly way, or if it's bad like just need some new parts or if it's an unknown issue that they need to chase down.

My money is there is an issue with the transmission. As greasy says, remove the cover and check both the variator and clutch nuts are torqued to spec and the belt is seated correctly.

Thanks for replies.

I will be spending today taking parts off to see if anything obvious. Only thing I've checked so far is oil and it wasn't that low.

You say "it wasn't that low".
Was it still above "min"?

Whoo, does this sound familiar…

Several years back, I was riding from central New Jersey to NYC, I had a very similar experience rolling along the New Jersey Turnpike, forcing me to make a hasty run for the service shoulder, and a few frustrating phone calls for assistance. The culprit? a cracked, and eventually broken, fuel-injector body. This likely happened a month or so before when I hit a crater-class pothole riding under the Brooklyn-Queens Expressway. There actually were a few minor telltale signs up to the moment of complete failure, but they were minor enough for me not to take too much heed. Rookie mistake.

So, among other things to have looked at, make sure the injector is given a once-over.

I don't know what you have found so far.
But I would put the Vespa on the center stand, start the engine and rev it.

On the center stand with the rear wheel off the ground the engine does not get the power load of the transmission.

If the engine revs normally very probably there is an issue with the transmission.