Hey Gang, I know this one isn't a Vespa but since the engine from a GTS 250 is in the frame and its running Megasquirt EFI I figured you all might be interested in it, and I hope you'll forgive me for sneaking a not quite Vespa in here...
I bought my Buddy, an orange 125, in 2008. I commuted on it daily and racked up a ton of miles on it. As I do with nearly all my vehicles I started to modify it. Back when I started there wasn't much in the way of performance information for the Buddy, so I started to forge a path to crazier and crazier motors. My 125 became a 161cc then 180cc (long before Genuine released a 170!), clocking in insane speeds and crazier parts. Finally one day around 2012 my poor little Buddy told me it had had enough and cracked a crankshaft on the motor. That was the end of that poor motor.
I picked up a used Vespa GTS250 engine and began the crazy task of grafting it into the Buddy's little frame. The project was going well until I got to electronics. I discovered that the GTS had an immobilizer system that I did NOT have the keys for, and Vespa would not sell me new ones back then. This brought my project to a screeching halt and the poor Buddy was stuck in the back of the garage destined to never see the light of day again.... Until a couple weeks ago...
I had just completed doing a Megasquirt ECU install on the Porsche motor in my 1980 VW bus and it popped into my head like a spectre of the past that Megasquirt can run almost anything, including my GTS engine. Out from under the pile of cardboard and dust I pulled out the long sleeping Buddy and evaluated where it was at.
It was a bit sad looking and I had misplaced some parts in the 10 years its been sitting, but it was mostly there. After some tests I discovered the GTS motor had VERY low compression (60psi) and likely needed a top end... eBay provided a bigger top end and my 250 became a 282cc. Two days of tinkering with wiring and a Microsquirt I had handy, and we had our first start!!
Since the Buddy is aircooled originally I had to figure out how to setup a radiator, and decided to attempt to rear mount it like some of the custom motorcycles do.
After getting some hardware to mount up the wheel I got to see how it would sit on it's own two wheels. It got a fair bit longer, but I don't think it looks bad that way.
I then got the cooling system all plumbed and tested. I don't yet have the correct fan for the radiator so I made due with a PC cooling fan. It worked. Kinda. The cooling fan didn't put out enough air to run it for a long time, but I could run it for 5 minutes or so before it started getting hot. Plenty of time to do some initial tuning!
Part of that tuning involved swapping the engine's stock narrowband O2 sensor for a wideband, which I had handy. This lets me see the exact air/fuel mixture ratio for tuning. Which means its no longer running pig rich with my guesstimate initial fuel table settings.
I Also got the charging system working, replaced the bad starter solenoid so you can actually start it with the starter button now, and replaced the seized front brake master cylinder so it'll stop when its ready to go.
Finally, after waiting for the radiator fan and a few more parts to show up, I got the bodywork all back on and for the first time in 10 years, its left the back patio and runs and rides! I took it for the first spin around the block its had in a decade this afternoon. I forgot how crazy small that bike is! Its not finished, it needs a few bits still, and a lot of tuning. It already seems like it wants to kill me... I tapped the throttle JUST A HAIR. And it spun the rear tire while moving. This is gonna be an interesting bike..
Now onto tuning! The Megasquirt seems to run the engine REALLY well, I have full control of the fuel and spark maps, and can tune all sorts of things anyway I want. It'll be a bit of a challenge to laptop tune it while riding around. But I'll figure out something!
Thanks for coming along on this little nostalgia trip with me!