Modern Vespa

This has been on simmer mode for the better part of a year now but as I near a new rear tire, the time has come to finish this so I can put it on and see if it works.
check it out.


cut it open.

gut it, preserving header legnth. Make silencer out of steel pipe and 1" ss perforated tubing.Modify exit pipe to accept 1" silencer tube

pack it and put it together.

pop rivet it closed using high temp copper sealant(fingers crossed), and paint the rivets to disguise the alteration.Note, the cover required a second donor exhaust so I could cut the cover larger than the opening in the first pipe.

forgot this shot.

Interesting...

I've always preferred the shape of the stock muffler to the cylindrical shape of most aftermarket "performance" pipes that always look like they're drooping when the bike's suspension is unloaded. I assume this mod preserves at least some of the stock muffler's catalyst as well, or is that in the perforated sheet?

It was my understanding that the perforated lining was the catalyst in that it got hot and further burned exhaust gasses. There was also a modest amount of pretty standard looking packing material sandwiched between the perforated lining and the shell.
I agree that the aftermarket exhausts look foreign to the vespa which is why I started messing with this. Notice the PM pipe has a loop in the header, presumably to preserve the legnth. Initially I just wanted to add a silencer internally that directly fedd off the header, but if Piaggio and Paul Meliki thought header length was important, who am I to argue. No idea if this will actually work, but very curious to find out.

Nicely done! Did you happen to measure the length of the header? I'd be interested to know where the piaggio designers placed the tuned length of the exhaust. Given the changes you have done on the intake side it may be worth shortening the exhaust a bit ;) need to talk at ROM.

I might have measured but I cant remember now. It's been awhile since I started this. Frankly wouldn't have known how those measurement could be adjusted to my advantage, so I just tried to keep it along the lines of those who did by not chopping off 2/3 off the header. You can try to explain it to me at ROM. I got those bell intakes BTW. Won't get to play with them till the BlueBadge come together though.

Well, I got it on last night and did a 30 mile loop in the hills. Initial impressions are that it is suprisingly quiet. Not at all obnoxious. Sounds less like a sewing machine and more like a thumper. A little thumper. Off the line possibly a little weaker and it seems to keep under 8 grand. Certainly not much over 8200, so a little disappointed about that. Popped a bigger main in it and took a spin tonight. Pretty much the same. It does feel punchier 6500-7700 and seems to be running cooler. My temp guage only goes to 230f (cht) and I had gotten used to the warning light flashing much of the time. It is running 195-212 now, of course that is a cool night ride so.... Anyway, seemed like I was hitting rhe rev limiter with the stock pipe, so I might switch back and see if it was my imagination, but I think I was getting a higher top speed with the old exhaust.

revs out to ~8000 huh? is that higher or lower than it was with the stock exhaust?

Seems like I could get 8700 pretty easily on a flat and hit the limiter on a downhill.

I coordinated the pipe swap with a new tire, oil change, hub oil change and valve adjustment. So the tire is a bit taller with the tread and my valve lash was pretty loose at .20 / .25. I guess by putting them back to the .10 / .15mm the lift is that much higher. Wonder if that would keep the power lower.

how about on acceleration, rather than at the rev limiter?

The variator responds to the torque being generated so if you've improved things it will run at a higher RPM (assuming no changes have been made to the variator).

Acceleration from a stand still feels about the same or less. Throttle response up around 6500-7500 seems punchier. I haven't changed from the 9.3g rollers I've been using. I started by going up to a 102 main fdom the 100 I had been using with the stock exhaust. Went up to
a 105. Not really noticing a difference. I may try a 108 and a 110 before I give up and go back to stock exhaust.

The project looks great with positive results, however why did you decide to rivet? I would have had it MIG welded to seal it.

The other day I took out the exhaust on my GTS300 and I was wondering why it weights like 50lbs...now I see why.

My verdict is in. The stock pipe works better.
After trying main jets up to 110 and not getting any improvement I've put the stock pipe back on. I am now pulling up to, and cruzing at 8300 topping out at 8600 on long flats. This project only pulled to 8000 and really needed a downhill to hit 8200-8300. Short of dyno testing I'm going to say any perceived gain was placebo. It did sound nice though. Back to the smallframr for me