engine ID next to ser Number?

seaguy · May 28, 2009

I have noticed what looks like 2CM3S stamped to the left of the serial number (149506) on my Commando . Anyone know what these stand for? I couldn't find anything on these.

chris plant · May 28, 2009

hi seaguy,instead of 2CM3S could it be 20M3S

grandpaul · May 28, 2009

Commando 750 series serial number prefix, not sure of the specific year range....

chris plant · May 28, 2009

HI SEAGUY,the early 750 commando had a 20M3 prefix the 20M3S was the prefix for the 750,s with the points in the timing cover

seaguy · May 28, 2009

You are correct. It is 20. Wasn't sure if that could mean combat. It sure has a lot of compression for an old engine with no rebuild. Thanks for the info.

swooshdave · May 28, 2009

seaguy said:
You are correct. It is 20. Wasn't sure if that could mean combat. It sure has a lot of compression for an old engine with no rebuild. Thanks for the info.

Not a Combat, those didn't start until 200001, I believe. That, of course, doesn't mean someone didn't up the compression in the last say, 35 years....

When you mean "a lot of compression", what are you comparing it to?

L.A.B. · May 28, 2009

seaguy said:
Anyone know what these stand for?

"20" Is the model code number for the Atlas, which the Commando engine series was a continuation of, so "20M3" is supposed to mean Model 20 (Atlas) Mark 3.

As chris plant has said, the 'S' was added to denote camshaft driven points, because 20M3 models had a separate points housing in the old 'magneto' position behind the barrels driven by a second chain.

The letter 'S' was probably chosen as the 750S Commando models were the first to have camshaft driven points.

seaguy · May 28, 2009

No comparison. Just 45 years of fooling with engines.

engine ID next to ser Number?

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