From:Jim Morrison
Subject:RE: RE: RE: RE: schnurle loop scavenging/Yamaha YA-1 Date:Thu May 29 14:52:27 2014
Response to:19534

From the Wikipedia on line:
"In the 1950s, after reestablishing themselves as manufacturers of musical instruments, Nippon Gakki decided to use the manufacturing equipment left over from wartime production to make motorcycles. Since the copyright on the RT 125 had been voided by the Allies, the company reverse engineered it as the basis for their first motorcycle. Nippon Gakki formed the Yamaha Motor Company in 1955 to build their copy of the RT 125 as the Yamaha YA-1, which was in production from 1955 to 1958."

I am always surprised at how many clones there were. Apparently WSK in Poland made a 125 in 1965 that was a copy.
(ref; Encyclopedia of the Motorcycle, by Hugo Wilson)

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.