Newbie with question

[zerk67]

What does an engine number like 25JRCA##### mean?

[MMasa]

25JDCA? Are you positive its an R?
Could it be a re Stamp?
Mark

[zerk67]

I do not have the bike to look at any more. I grew up visiting and looking at it as often as I could. I recall the stamping of the numbers was very deep and clear. However, I did not write them down; the owner, my uncle, did that for me but he may have taken the numbers off the registration slip. His writing is very clear as well. The only possibility that he was wrong would be that the registration slip was wrong and he never noticed it. It was last registered in 1945, if I remember correctly. Is the "R" the only thing that is puzzling to you? What does the CA mean?

[MMasa]

It just indicated that the motor is fitted with aluminum alloy Pistons. In 1923 and 1924 there were the following 74" models.
JD and FD
These were the standard motor with the standard iron alloy Pistons

JDCA and FDCA
These motors used aluminum alloy Pistons.

JDCB and FDCB
These motors used an iron alloy piston that was lighter than the standard iron alloy piston.

In 1925 they dropped the JD and FD models and only had the DCA and DCB models.
I've never heard of a JRCA.
Mark

[zerk67]

Thanks for the info, Mark. We'll assume the R was really a D on the engine.