Modern Vespa

I'm currently working on a 1972 sprint 150 V project and excited with all the information I found on this forum. Vespa was in great cosmetic condition, but the mechanical left a lot to be desired. I've completely rewired and replaced all the cables with SIP products. I've also relied on David at Scooter Mercato for various other parts, including replacement hubs, brakes shoes, and tires.

My 20/20 carb was beyond repair and picked up a BGM 24/24 and one of their Cosa clutches. For exhaust, I went with the Malossi box since it was readily available from SM and waiting on the BGM 177 cylinder to arrive. I considered the Malossi aluminum kit could not stomach the premium price tag.

If anyone could offer any guidance on the cylinder installation and jetting, I would greatly appreciate it.

welcome! good looking bike. you've come to the right place, you will get some jetting suggestions shortly...

your air bellow is wrong or installed incorrectly (it goes over the hole not in the hole)

Thanks Greasy. Actually it's still being installed. I needed a break after attaching it to the frame. Not a fun project.

heat gun to soften the rubber, then fingers inside the carb box through the opening to stretch it over the box.

You are not missing a whole lot on the Malossi 177 Aluminum kit, on paper is a killer deal and the parts are absolutely top. Even details like the cylinder head finish or the opening of the exhaust spiget is magnificent. All that I just said is true, I have one and I also have a Malossi cast Iron kit, both kits the newest. The cast Iron performs equally than the aluminum in pure performance acceleration, tested by yours truly using CHT gauges and acceleration instrument on two equally geared engines(PX150 and a Sprint Veloce with LML engine).

You answered your own question regarding that you did not have the stomach to pay the premium for the aluminum kit. I personally don't have anything against it, at the end of the day I have one but I just don't see a tangible difference. Further more, even when talking with David at SM even he said why changing it if you already are happy with the cast iron one?.

I can't compalin on the all 177 Malossi kit but the cast iron version is also a beast for a much more reasonable price. I have done close circuit road loops where I would do the same route just to test them and I can not see a performance difference between the two on at least 30 plus minutes of soft and hard riding.

As per the jetting, I would say start in the 125 MJ specially if you have a exhaust. I am running a Malossi box and a SR3 on the other one, tons of midrage and top end.

As per cylidner kit installation I never done neither the squish nor the piston ring gap, I am simple when it comes to cylinder kit. No fails off course, nor that I expect a fail. I guess you can finesse the install following some of the write ups regarding squish and piston ring gap. I would say though, make sure that your carburator gasket is adequately opened to match the cylinder rotary opening, the carburator box to the carburator. You might have to cut the gasket a bit bigger and maybe trim/file the carburator box otherwise the bigger carburator wouldn't flow as good due to restriction (restricted flow).

Thanks for the feedback Scooterist. As I sweated over getting the right squish after trying all three supplied base gaskets finally got it to 1.08mm, so just in spec. I was highly considering just scrapping the BGM and ordering the cast-iron Malossi (based on some of the detonations I've seen from the early BGM kits that could always happen in the future).

The build is not been without its challenges. I dropped the clutch woodruff key forcing me to tear down the entire bottom end. Shockingly, there was no key in the engine, so it must be lost somewhere in my garage floor. However, I did identify a damaged driveshaft selector bearing and a slightly worn cruciform. Also, found out from SIP that the wiring harness I installed is not sufficient for the SIP Vape 12V system.


Overall, once I replace the bearings, oil seals and upgrade the clutch, cylinder and electrical system, I should have a very nice scooter. All these things I plan to do, I just not plan to do them all in the beginning.

Nice work.

Here are some additional photos. Vape installed and running perfectly. My current stack is 120/BE4/118 MJ.

I'll eventually upgrade the crank but pleased with the BGM cylinder and clutch. The Malossi exhaust is certainly high revving but not sure what other one I'd change it out with.