Maico Prototype

[Brian Catt]

I have just found this pic, it has a normal 2 stroke inlet location, but an overhead camshaft drive. Presumably it has transfer ports, or some other mixture delivery to the top, so would the 2 stroke pumping be beneficial to mixture delivery, and presumably it has reed valves to shut the inlet to crankcase pressure. It appears to have crank mounted electronic ignition.

[Brian Catt]

No offers of explanation, so perhaps the next one will be easier.....

[Andy Z]

Maico prototype

Hi Brian,

I think there were no suggestions on the Maico engine mainly due to the lack of any info on the internet on the subject. Looks like a rotary exhaust valve, I wonder if it worked?

Is the Sachs engine a split-single?

Cheers,
Andrew
#190

[Brian Catt]

Andy, I think the Maico has a conventional SOHC exhaust set-up, see the half speed drive. If it was a rotary exhaust, surely they would time it at engine speed to give a 2 stroke action. I think it has a reed valve inlet rather than conventional piston or disc inlet.
The "Sachs" engine is actually a Hercules. Look at the relative positions of the carb/inlet and exhaust, does that give any clues? Split singles usually have piston or disc inlets.

[Andy Z]

Funnily enough, seeing the carb so high up made me think of a rotary valve Cross engine, but that looks like a 2-stroke bottom end.

Must be a rotary (wankel), but the design looks a bit odd with the rotor chamber being separate from the rest of the engine.

I see what you mean about the 1/2 speed drive on the Maico. I've seen a few works prototype 4-strokes, which at first glance looked like 2-strokes.

Cheers,
Andrew

[Andy Z]

Blimey, found one running on youtube! Looks slightly different though.

http://www.youtube.com/watch?v=ow5fNz5BqD4

[Brian Catt]

That's my correspondent pal Marcello! Yes, it's a Wankel, but these were built with the rotor going round in the (almost) horizontal plane, as opposed to the vertical on most other applications. This means there is some type of bevel drive in the bottom of the engine, to convert the drive into a conventional gearbox with chain.
What you see as the "cylinder head" on that engine is actually the top rotor cover and will house the main bearings for the primary crankshaft. The inlet port is let into that cover, unlike most competition Mazda engines which feature more efficient peripheral ports, similar to the exhaust. The plug(s) will be in a similar place to the exhaust port, but on the left side of the bike.
There is another video on Youtube of Fritz Witzel's son riding one of the production based 2000 GS models which were ridden in the IoM. These featured the vertical plane engine.

[Andy Z]

Many thanks Brian, all very interesting info!

Cheers,
Andrew

[Brian Catt]

Pics below of Marcello's shed......