These guys are more commonly known as a "Sachs Madass", which came in 50cc and 125cc flavors. The "AMG Nitro" is a Canadian variant of the 50cc version, imported by "Alliance Moteur Groupe" of Quebec. The Sachs Madass was still available here, mind you.
I first saw a Madass parked outside of the local scooter shop, which was just a few blocks away from where I lived at the time. I loved the looks of it, young as I was at the time. Couldn't afford one...young as I was at the time. Rather like the Fiero, I put it on the back-burner and never forgot about it, unlike some other things.
When I got my Honda C70, I noticed these guys used the same basic (clone) engine. It wasn't a Madass, but I enjoyed restoring it and riding it for a year or two:
This Nitro popped up when I was doing my usual daily searches through local online classifieds, for $500. The owner couldn't get it started after having put it away for the winter, so he was selling it cheap. They typically go for three times that - or more - in running condition. I tried it on for size - it looks so small in photos, and I'm tall - and it fit, so I took it home with me.
It needed a new battery, and with extremely limited space for one, I invested in the correct one. Even with a working battery, it was a pain in the butt to get started the first time. But I got her going. Made sure she was road worthy and took her for a ride.
She was pretty gutless on take off, even with the 72cc "big bore" kit that was installed on it. These 2-speed automatics aren't stellar. First gear isn't low enough, second gear isn't high enough. She couldn't really take off on hills with two hundred pounds of me perched atop her, and she was absolutely screaming when cruising at posted speed limits in town.
I never got her starting reliably...she had idle issues...she died once too often and wouldn't start up again until she had sat for a while, as if she was flooded. I finally came to the conclusion that the piston rings were fried (presumably from making it scream all the time), and no amount of adjusting the carb and whatnot was going to get her to ever idle or start reliably.
So...I stole the engine out of my rebuilt C70. She wasn't half as pretty any more, and I had little interest in riding her, so it wasn't a hard decision. This was a 110cc, 4-speed semi-automatic I picked up on ebay. It was getting ~100mpg on the C70. I'm assuming/hoping it will do the same on the Nitro.
I repainted the engine with charcoal grey metallic wheel paint while it was out, as continuing the black(dark, anyway) blue paint theme of the frame and wheels would look better than a bright aluminum engine. I liked the theme on my Miata, after all.
The electronics(ignition)/charging systems were a bit different. The 110cc uses a crude center-tapped magneto, whereas the Sachs engine (even though it was a Nitro, Sachs was stamped on the engine case) had a proper 3-phase generator. The 110c was designed to run without a battery, if necessary, and the CDI did
not depend on the battery to provide power. The Sachs did.
Comparing the spark between the two while cranking the engine over, the battery dependent CDI gave a far superior spark, no matter how fast or slow the engine turned over. The magneto-dependant one would either not spark or spark weakly except at the fastest/hardest of kick-starts. So I re-wired the 110cc to use the battery-powered CDI, for dependable starts.
The Sachs motor also breathed better, as attested to being able to get the silly little 72cc engine up to 65km/hr, in spite of being a 2-speed. I used the carb from it, which was larger than the one that came with the 110cc.
The combination of the battery CDI and the bigger carb was wholly better than the originals for the 110cc. I blipped the starter and she fired right up. No more extended cranking as before with the 110 setup, and no more lack of compression making it near impossible to start from the Sachs motor.
I rode her around the last bit of last season like that, fiddling around with things here and there. She was my weekend toy to bomb around on and enjoy the freedom that comes with 2 wheels.
Fiddled around here and there? I never stopped fiddling around. The stump-pulling torque was great fun on take-off, but the ~55km/hr top speed wasn't. My 4-speed engine is both low-geared, and
not rev-happy, like the 72cc was. Meant for a smaller engine, the rear sprocket is huge...and replacements are stupidly expensive, since almost no one makes them. Hence why I ordered as large of a front sprocket as I could fit, and put it on after the weather turned for the season last year...
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