Nearly finished this project. You may have seen in earlier threads that I was looking to improve the gearing on this Mission Space Genie II. I bought a Sachs 3x7 hub as suggested by a forum member Bkhyte (?) but bought the wrong size rim.... If any of you have 16in wheels; there are two different sizes of 16in!
Anyway, the wheel just about fits with the mudguard (fender?) removed, but then the brakes didn't. So my LBS welded a plate just above the original bridge and I drilled a hole to fit the brake again. Hey presto, the wheel now fits.
To add to complications, Sachs apparently no longer make the hub and it came without cables. So, I've bodged a connection between the chain and the cable. The other end has a friction changer because I didn't know what distance the index intervals would be.
So now I have 21 gears...
I've also had made a massive 800cm seat post - my friend who owns a machine shop made it, unfortunately out of stainless steel. Again, because it isn't knurled, it slowly slips down during riding and I had to adjust every ten miles or so. A few minutes with a drill and I have put an allen key (hex wrench?) through as a stopper. Works a treat.
The bike is remarkably comfortable - I did a 35 mile ride on it the other day with no ill effects. The mtb bar ends really help with that. I do find climbing out of the saddle a bit strange, but I think that is as much to do with the overall different position more than anything untoward.
The final piece will be to replace the 50cm cranks with 70 or 72.5. This will, I hope, get rid of the choppy feel of the ride and make it just like a road bike. Also need to make a rear mudguard (fender?) out of some plastic to complete the job. All for less than £200 - oh, plus the original £50 I paid for the machine on ebay.