Schumann Motor Works

Schumann Motor Works Specializing in vintage motorcycle cylinder head services and custom valve train components.

Honda CB350 four head build. Guides in perfect condition but needed a valve job and fresh seals.
09/04/2026

Honda CB350 four head build. Guides in perfect condition but needed a valve job and fresh seals.

Look at this gorgeous CB500 that’s available here in the Pacific Northwest! Even has a custom wooden headlight bucket an...
09/03/2026

Look at this gorgeous CB500 that’s available here in the Pacific Northwest! Even has a custom wooden headlight bucket and some sort of race mod suspension upgrade to the right fork leg.

CB350 race head with 5.5mm stem conversion. This one took some work to make right. The guides and spring kit are mine, b...
09/02/2026

CB350 race head with 5.5mm stem conversion. This one took some work to make right. The guides and spring kit are mine, but the valves had been sourced from someone else and much of the work to the head had been started. Seats appeared to have been stone cut 45 degree only, no top or bottom angles which with 1mm oversize intakes made for a massively wide seat. I did a proper multi angle job with a throat cut to accommodate the oversize. The valves themselves were too long for proper tip length to achieve valve adjustment range so material had to be removed, retainers modified, and lash caps machined to fit. The keeper grooves were also in the wrong position for proper spring installed height. I used some modified OEM spring seats removing .020” from the intakes and adding .030” shims on the exhausts. The resulting difference in final tip to groove distance between intake and exhaust valves tells the story. The exhaust valve stems were also .001” larger in diameter than the intakes, which is backwards. Exhaust valves typically run a smaller stem diameter for thermal expansion. But it’s good to go now!

09/01/2026

1982 Suzuki GS1100E group ride departure.

08/31/2026

1982 Suzuki GS1100E mountain highway ride with modern sport bikes. About 10 positions back in a group of around 60.

Did a group ride up to Larch Mountain Oregon Sunday morning on the GS. The view and weather was perfect!
08/31/2026

Did a group ride up to Larch Mountain Oregon Sunday morning on the GS. The view and weather was perfect!

1972 Honda CL175 head build. Made new valves and bronze valve guides with modern seal upgrade. Spark plug inserts in bot...
08/31/2026

1972 Honda CL175 head build. Made new valves and bronze valve guides with modern seal upgrade. Spark plug inserts in both holes.

1973 Kawasaki Z1 head build. New bronze guides, spark plug inserts in all 4 holes. Customer supplied stock replacement v...
08/28/2026

1973 Kawasaki Z1 head build. New bronze guides, spark plug inserts in all 4 holes. Customer supplied stock replacement valves.

Hydraulic damage from tightening a cam cap bolt with the hole filled with oil.
08/27/2026

Hydraulic damage from tightening a cam cap bolt with the hole filled with oil.

CB175 valve set wrapped up. I often just buy these rather than make them as NOS ones are available for pretty cheap but ...
08/26/2026

CB175 valve set wrapped up. I often just buy these rather than make them as NOS ones are available for pretty cheap but currently there aren’t many available in the US and the overseas ones are lower quality reproductions with slow shipping times and duty fees. These I can make quickly when needed and are better than OEM.

Address

8613 SE Strawberry Lane
Milwaukie, OR
97267

Telephone

(503) 939-7395

Website

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