Also the mech hanger is unthreaded.. how does it attach?
My wife had a Gitane with an unthreaded mech hanger and the Simplex rear mech came with a bolt that went through the hanger from the inside and into a threaded portion on the top pivot of the mech. Like this one:http://www.velobase.com/ViewComponent.a ... &AbsPos=48
That could be possibility if it fits your dropout. I can't see the pictures at work so apologies if this is a stupid suggestion!
The original (and probably later also) Simplex Prestige mechs were something like that although I remember (possibly wrongly!) that the bit that went though the hanger from the rear was 'female' threaded and the 'male' part was on the mech. I had one of them BITD because the hanger in my frame, even though it was threaded, was ovalised! A Campag mech would not screw in so I had to file the diameter of the 'female' part down slightly to reduce its diameter to fit through the hanger hole.
Cyclo rear ends should be threaded so therefore, is the frame dropout possibly a Simplex one and not a Cyclo? It should be stamped on whatever it is. If so, the lever boss should also be Simplex and therefore unique, accepting only Simplex levers. If there is only one boss on the right then a rod-operated front mech is the right way to go.
Early Benelux and Simplex mechs and levers do turn up at jumbles, e-bay etc. but they're not very common. However, finding them is all part of the fun - isn't it?
Benelux Mark 7 mechs were made for 3 x 1/8-4 x 3/32 and 4 x 1/8-5 x 3/32 and were marked accordingly. Always check the markings stamped on the mech to make sure it's the one you want.
A 125 (actually 126 officially) rear end basically dictates a 5 - speed set-up although 6 can be squeezed in occasionally. A 'compact 6' block is better which is only slightly wider than a normal 5.
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