I thought I'd sign in for the first time and see if I could revive this 8-month-dormant thread, which I stumbled across while trying to find a reliable 50 MPH mechanical speedometer for my 70cc 1978 Sears Free Spirit, Puch E50, one of my three mopeds. I've had to reject a succession of Treatland speedos that did not work or last, although the folks there make a special effort to be helpful, and usually are.
I also wanted to add my thoughts on who has the fastest Puch. For me, the real question would be, "Who has the most healthy brain?" My last and best airplane cruised at about 200 MPH, and in the air, 100 MPH, 200, or 350 are all about the same. So it was not unsafe. I've also had a bunch of fast motorcycles, but I've never been so foolish as to operate one above 100 MPH, even if it can. At that speed, it feels like you have almost no contact with the road; you are a projectile, with few options except easing off the throttle. I've loved my 1100 cc Yamaha Virago road bike for 27 years, but hold it to 75 or well below. It's about fun, not suicide.
Which gets us to mopeds. My strong opinion is that anybody who even wants to run a 100-pound two-wheeler above 50 MPH is a rather foolish and possibly inexperienced person, and is perhaps not long for this world. I've converted two of my three mopeds to 70cc and am finishing up the third engine. The first two are fast, and I have put a lot of miles on them. Both do about an honest 50, but it does not feel safe. The feeling reminds me of riding a much heavier motorcycle at 100 MPH. Stability is zilch.
Again in my opinion, the best reason for hopping up a moped above 50cc is that it actually enhances safety, it doesn't detract from it. Having a little more power, not a lot, makes it easier to blend in with auto traffic, in rural smaller towns, like the one in which I live. Being able to keep up with traffic, and not impede it, is a wonderful thing. Auto drivers don't become angry and try to run you off the road, or tail gate you, because they can't, without breaking a speed limit. I've survived for a long time, and sometimes in a risky occupation, so it made me appreciate the attractiveness of continuing to be around. Running an almost weightless moped at 60 MPH is not the way to do it. Please guys, don't even try. But if you do, and succeed, please don't advertise your bad judgement by bragging about it. You're bound to encourage somebody with even worse judgement to try to top you, and get killed.
But again, top speed is not a good reason for boosting moped power. It's safety, and just a little bit more horsepower really does make your light ped safer, if you just hold it down responsibly, speedwise. I like 35 - 40 MPH in the Ohio countryside, just enjoying the sights and smells. It feels right. I don't feel like the tiny engine is about to blow up, or that if I hit an unseen bump, I and the 95-pound bicycle will be bounced into the ditch and extinguished.
Be careful, while enjoying the endless fun these toys can give you, way into your second childhood. I'll bet I'm way ahead of all of you on that. I tell people that I don't plan on dying anytime soon, but if I do, it will probably be falling off a motorcycle at age 95.