Topic: head markings

[comcrx]

ok, this could turn out to be an idiotic question, but when I was doing my valve clearances yesterday, I noticed a marking between the intakes for 2&3. it looks like it was cast into the top fin, rather than being stamped, and it has an "NM" inside of an oval, then 300

is that a standard marking that is on all of our machines, or is it the marking of an aftermarket head? I thought maybe it was HM, for honda motorsports, but it really looks more like an N

has anyone seen this before?

[upperlake04]

The cast characters on the top fin between 2 + 3 intakes on my 78 750F reads HM inside a horizontally elongated oval and 410 to the right of that. The 410 is is in line with the camchain tunnel. The head is an original Honda part and the product code number is correct for the year.  The  verticals of the H are tilted to the right at their tops and the connector line is horizontal.  The casting is a little blobby and if yours is even a little less crisp, the H could look like an N.  FWIW

[comcrx]

thats exactly what I wanted to know, Thanks!!!

[Jerry Rxman Griffin aka MuthaF'er]

I have both a 75 CB750F (bike) and a 78 CB750K (Engine only). Both heads have 392 cast into them. The 392 is the designation for the 75 CB750F. This same head should be found on 75/76 F0/F1 as well as 77/78K.

Lets see how many head numbers we can accumulate and put a list together for FAQ.

Jerry 

[Jarkko68]

I think it is "Nice Motorcycle" NM