250 ETZ steering stem question

[ajb235]

250 ETZ steering stem question.
i bought a bottom yoke with stem attached to make into a top yoke for my cafe racer. I cut and removed the stem, and opened up the hole by 5 thou to fit over my original stem. No problem. However when I started to modify my bottom yoke in the same way, removing metal from the webs, I noticed that my stem is a lot thicker than the one I removed from the new bottom yoke. Mine is 4.6 mm wall thickness, the other one is 2.3 mm wall thickness. Thread on the end is also different.
my bike is 1983. Anyone know what bike or year the other stem is? Maybe from a 125?
Quite a difference in weight, which is my concern for the cafe racer.
any info appreciated
Jim Baird's photo.
Jim Baird's photo.
Jim Baird's photo.

Sorry can't post photos, hope you can understand my point

Jim

[EmmasPapa]

The early ETZ 250 was equipped with the 5 mm wall thickness, the thread is M30x2. Later then, after 1983, it was changed into the 2,5 mm thickness with thread M30x1,5. Main reason was saving material resources.

Also see viewtopic.php?f=3&t=36990 latest article from "ralle". Sorry, it is in german.

[ajb235]

Thank you!

Jim

[g-spann]

I think, the thicker stem was originally designed for the sidecar-bikes because of better stability in cornering...those without sidecar were actually assembled with the thinner ones...but sometimes, in absence of the thinner ones, they used the thicker ones to assemble the normal bikes without sidecar...

Greets...

[ajb235]

Thanks for the information. Now I know that I can safely use the 2.5mm wall tube steering stem on my cafe racer, which is going to be a lightweight bike.

Cheers

Jim