From:Dave Hennessey
Subject:RE: RE: RE: schnurle loop scavenging Date:Wed May 28 22:56:06 2014
Response to:19532

You're right - it doesn't make much sense. I can't remember now, but the YA-1 didn't appear until around 1955. So I guess the designs were floating around the Internet for a few years and the Japs downloaded them. Oh wait...

I know that this is off topic, but while I was looking at the Hummer relatives, I noticed the Yamaha YA1 and wondered how Yanaha ended up with the license for the DKW?

I get that the US, England, and the USSR received the tooling / license as war reparations, but somehow Japan doesn't make sense to me.

Just wondering...


Here's a photo of a Hummer cylinder from the Service Manual - you can see the transfer ports in the sides.

The crankcase has channels leading into each side of the cylinder at the bottom.

Browse over to and click "motor" That's a 1941 DKW RT-125 I used to own, and you can plainly see the channels running from the crankcase up into the sides of the cylinder. The Hummers look similar.

Looks pretty Schnürle to me.

shows the BSA, Russian, and Yamaha copies.

I've never seen a RE in person or even a good photo, so I don't know anything about them.


Forgive me if this message shows up twice, I seem to have lost the first message a few minutes ago.

When DKW made the RT 125 they used (invented?) Schnurle Loop Scavenging to make the engine more efficient. Apparently when Royal Enfield made their copy (model RE) they missed that feature and had an inferior engine. Did any of the so called "Hummers" use the Loop Scavenging design?
Just curious. I have been having fun looking into the history of motorcycle development recently.