Modern Vespa

Does anyone know the diameter of the stock exhaust. Tbe bit where the actual graphite bush goes?

Another rider gave me their new stock exhaust from a 20 HPE after they upgraded so the next time I swing by the storage garage where I keep it, I have a micrometer and can measure the inside and outside if that works for you.

Note: To install a new bushing you pretty much have to use the expander tool scooterwest has > https://www.scooterwest.com/tool-exhaust-expander-toolex.html < to drop it in there, otherwise you'll have a difficult time.

Not always. Mine has slid in easily enough the last time or two. There's also a hack....using (IIRC) a 1 1/8" socket used as an expander. In case you have one laying around, it's an option....otherwise the real deal isn't all that much more expensive.....

People have gotten by with prying the tabs back slightly as well...YMMV

The gasket size is Outer Dia = 38.5mm
And Inner D = 32mm

1- Outside Diameter with Clamp 1.70 inch
2- Outside Diameter without Clamp 1.60 inch
3- Inside Diameter with Bushing 1.22 inch
4- Inside Diameter without Bushing 1.50 inch

As per fledermaus's post, use an 1 1/8" socket on an extension bar to just tap into the bushing area. This will tap right down as far as the bushing goes and open up the exhaust. To avoid the bushing being crushed or damaged as you tighten the exhaust clamp it's imperative to make sure you start with the correct shape to the pipe. And remember, only tighten to the specified torque otherwise you'll damage the bushing and it will fail very early. Overtightening is the main cause of bushing issues and broken exhaust header studs. That joint must be able to slide and move during use of the bike. Overtightening stops that happening and stresses the exhaust studs.