Puch fore and aft twin

[Greybeard]

This engine is a twin but fore and aft. Both pistons use one bigend. One of the conrods pivots on the other one. I think they share a combustion chamber.

[groily]

Very weird beasts GB. The 'split single' with those oddball rods, single combustion chamber as you say.
You wonder 'Why?' sometimes! But they do work.

[chaterlea25]

Hi All,
In my Youth I had several Puch 175's they could be picked up for nothing or almost that back in the mid 70's
They would burn out the front piston if they suffered fuel starvation or incorrect ignition timing so many were left to ons side and not repaired
I must have covered 20K+ miles on one, I remember 15k in one year
They were lovely to ride and very torquey due to the asymmetric port timing, fairly thirsty though about 60mpg
There is a tapped hole in the crankcase where you insert a pin when the pin fits into the flywheel the points should be just breaking, soo easy

I have often thought about getting another 
John

[Joolstacho]

Groily I think the "why" is that it was intended as a sort of supercharger device, The little piston compressed more mixture for the big one.

[chaterlea25]

Hi Jools,
Both pistons are the same size,
One advantage of the design is that the transfer ports are to the rear cylinder so the fuel mix does not a chance to escape out the exhaust ports as tends to happen on a conventional 2 smoke
This advantage was largely negated by exhaust tuning developed by Ernst Degner (MZ and Suzuki)

John

[Joolstacho]

Didn't they make a liquid-cooled racing version too?