Shimano FF front freewheel

I have a couple of old schwinn suburbans (76 womens 78 mens). Both have the shimano FF system, the womens is also positron. It's been quite a while since I serviced them, they are difficult to service, but I can. As I remember they were well built, but maybe not up to motorized bicycle standards.

Anyone jack shafted one of these shimano FF? I have a 49cc china that would fit it well, and they all gather dust a few feet away from each other.
The mens was my dads, a 10 speed and requires his legs to straddle the bar, mine are too short, but I still ride it once a year. The Womens was moms and has a 5 speed positron. Its in great riding condition still, and has an absolute ton of miles.

perhaps a pic worth 1000 words.



stir up any memories?
I have not seen anyone build one?

Nice to hear somebody else enjoyed the system too. They make such a nice sound in freewheel, unlike any other bike I've ridden. The womens with the positron and ff was really neat coasting and clicking as it shifts. It wasn't until recently I found people are not very fond of the positron, but I think its great.

In interesting fact, the rear sprockets have dogs and springs. If your chain was to become jammed the rear wheel could freewheel without the chain moving, but there is considerable resistance to do this. When assembled the gears are very tight against each other. each rear gear can turn independently. If you are nuts enough to take the rear apart, be very careful those dogs and springs are very small and can take flight, If i remember each gear has 3 dogs/springs. it is tricky to stack them without getting frustrated.

If I cant motorize this, they are still not going anywhere. I have too many memories on them.

maniac57 said:

Could you not simply use a standard freewheel rim? The gear spacing is the same.
I too thought about jackshafting one of thes.... at least until I got offered ten times what I paid for it!
SOLD!

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I think that you could but it would be confused where to freewheel, and probably cancel the ability to shift during coast, or at least make it erratic.

That does make me wonder however, if there is enough force to start an engine from the chain without that rear gear slipping. I bet not, and these cranks are not easy to widen for a pullstart...

going to have to think more about this one.

turnofftheradio said:

I think that you could but it would be confused where to freewheel, and probably cancel the ability to shift during coast, or at least make it erratic.

That does make me wonder however, if there is enough force to start an engine from the chain without that rear gear slipping. I bet not, and these cranks are not easy to widen for a pullstart...

going to have to think more about this one.

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Ok, I thought...

It would be easy to just tack weld ONE gear in the rear as a start gear, maybe the big one makes most sense, since at speed, I'd never be running in it.

maniac57 said:

The engine will take care of the shifting. Since the engine will keep the front freewheel spinning, there should be no difference between the two when motorized.
Only while riding normally would the rear freewheel cause any shifting issues.
It would still start like any other shift-kit motorbike. You have to keep pedaling while starting.

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Doh, I overthought It
thanks for bringing me back to reality