First thing I change on a Vespa is the exhaust, as it's so fundamental to 2 stroke power, and stock is so de-tuned.
I originally bought a PM24ev by the British PM Tuning. I did so because I have a well designed smallframe (PM40ev) exhaust by them, and figured they would be leaders in the fit and performance areas.
The PM24ev is decent, and can be found on ebay for a decent or even 'bargain' price. Worth noting however, you have to buy the exhaust can as additional extra. This is fairly common with expansion chamber exhausts. I bought my can from PM Tuning's online store as to guarantee proper fit, something that can't really be assumed when buying aftermarket parts for obsolete two stroke Italian scooters.
The very sturdy bracket works well enough to attach to the swingarm. It has a black rubber spacer to reduce vibration transfer to the frame.
With the can cost summed with the expansion pipe and hardware, it's around $425 Canadian Pesos all in.
The pros are it's an expansion chamber, so you get that sweet powerband pull which for me is the true joy of a two stroke. Tiny engine displacement but lightening acceleration. Revs higher than stock.
Great welds on thicker steel, reinforcement on weak bits.
Decent instructions, including jetting suggestions and stock carb filter "heart" drilling (makes a small but noticeable difference).
Fairly 'easy' fit with exception of cutting a bit of kickstand off.
The cons are worth noting however.
First, mild steel rusts, so you'll want to spray this heavily with high temp spray paint, which slows you down in terms of testing it out
And before that you'll want to strip the oil off with nasty degreasing solvents like acetone.
The manifold and main chamber body have spring attachments, which is great. Unfortunately mine leaked a thick black ooze due to an easy-fit-but-poor-seal. PM literature, a one-page photocopied piece of paper, suggest using high temp silicone gasket goo, which helps but doesn't solve the issue. Also it adds to the total cost (with the spray paint and acetone) and requires curing before use. I'm not that patient with new hardware and just want to bolt on and go.
The manifold comes with no way to keep from slipping off. I removed the tightening band from the Sito it replaced, and attempted to use that to tighten down the PM on the exhaust stub. Manifold kept slipping off the stub regardless of how over-tightened the band was, likely due to the porky weight of the over-built steel manifold plus gravity plus two stroke exhaust pressure. I bought some stainless plumbing straps of a good size and tried those, and still no luck. I eventually had a MacGuyvered Sito band plus Stainless plumbing strap plus spring hooked from plumbing strap to a hole on my aftermarket cylinder's fin. It mostly held, most of the time.
What every other performance chamber exhaust does is have loops for springs to hook the manifold to cylinder fin holes and/or cylinder shroud screws. The PM even had loops for springs where the manifold and chamber body meet, so it's not like they haven't realized the utility of loops and springs. Weird. If I was to keep this exhaust I'd have a welder add the loops at the exhaust-stub end. It's pretty standard to have and makes accidental slip-off impossible in a very vibration prone environment.
Another con, though more standard for this style of left-hand exit exhaust, is the need to cut a section off the kickstand arm, and to drill a new hole for a spring through the remaining portion.
Finally, this is a loud exhaust. Like Sito loud. Perhaps partly due to imperfect seals even with gasket sealer goo to bot exhaust spigot and slip-joint-with-springs. I thought it might be the can packing though I later discovered the can works fine on another expansion chamber.
So I feel like I'd give this a "7" and for the price, even less. Just IMHO. Decent speed/revs/power much better than stock or Sito. Built like a tank with solid hardware. But frustratingly prone to slipping off the exhaust spigot, black juice leaky, and louder-than-it-should-be compared to similar (and better) exhausts.
For $400+ CAD, I expect better. Especially for a British hand made item. Especially for an exhaust that's been in production this long; the problems this exhaust has have been solved by other companies quite some time ago. I feel the PM Tuning may be eclipsed by the other Euro expansion chambers.
Bittersweet.
Pics forthcoming.
⚠️ Last edited by stimuli on UTC; edited 3 times