Modern Vespa

hi i wonder if anyone has any suggestions i have a preleader et4 125 it vibrates alot on idle and has become really jerky at low revs when on full throttle its great but obviously cant go around at full speed thanks

Is it the Jack Links edition?

sorry to sound stupid but i have no idea what u mean by that

I sincerely apologize. I know you must be frustrated that your Vespa isn't running right. I just saw the thread et4 jerky and I couldn't resist. (Like beef jerky... Jack Links is a brand)
Sorry again

oh der stoopid me haha

St least this way it gets bumped to the top so maybe someone can offer some technical help. Portsmouth New Hampshire or England ?

Have you been keeping it serviced properly?
Could be a few things.
Other than missed service items, carb jets could need cleaning.

Since it runs well on full throttle, the easiest place to start would be opening the variator up to clean out any dust and grime and replace the rollers if any even slightly out of round. (You didn't mention how many miles on the scoot or if it gas been sitting for extended time, but most people seem to change out their rollers and belt at same service time). I would also run some Seafoam (a carb cleaner / fuel stabilizer here in the States) through the gas incase there is any gum or clog in low speed jets.
Beyond basic troubleshooting and maintanace, I am not much help. Good luck - doesn't sound too serious.

Does it sound like a bag of pebbles bashing together? - if so I'd check the variator / variator rollers.

Fabio

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try checking "silent block" also known as swingarm bushing.