Topic: CB750 engine numbers & Crankcases

[01Thomas]

Hi everyone

I have bought a joblot of CB750 spares, among them crankcases with the following numbers (all prefaced by CB750E- ):
A: 1035897
B: 1097878
C: 2071504
D: 2522058
E: 2551078
Going by the info in Pete Shoemark's book "Honda CB750 SOHC Super Profile" (*1), case #A is a K0, #B is a K1 and #E is either a K6 or F1. Is this correct, and could anybody fill some of the other blanks?

How accurate is Shoemark's book in general?

Is there anyway to tell if any particular upper & lower crankcase halves constitute a matching set?

Finally I wish you all a Happy and Merry Christmas!
Thomas


(*1) published by Haynes in 1983.

[mrbreeze]

Not familiar with that book but there is a handy reference page on the Honda chopper site. You could check your findings against that.

[Bowswell]

http://www.satanicmechanic.org/enginemods.shtml

[Dream750]

Never seen the Pete Shoemark book.
 
These are the Honda (published) engine serial numbers that I have:
 
750 K6: 2428762 to 2476663
 
750 F1: 2515094 to 2563530
 
Going by the Honda engine serial numbers, your 2551078 would be a 750 F1

[mrbreeze]

http://www.satanicmechanic.org/enginemods.shtml

I like the avatar!!

[HondaMan]

http://www.satanicmechanic.org/enginemods.shtml

I wonder: are those the mods for Euro bikes, or something? They aren't anywhere close to my old notes. It seems 'sketchy'.   

Just one example: there are 4 distinctly different clutches. There were 2 in the K0, another that happened late in the K2, and the final [major] change to the F0/K6 bikes that stayed to the end. Those don't show up on the list, except an obscure reference to "7 plates instead of 8" during the K0. (?)

The crankcases changed 4 times, too: the sandcast not being counted, here (it had 3 of it's own cases before diecast ones came along). The cases changed during the K1, again partway through the K2, at the K4, and for the F0 and again for the K7/F2.

[Jonny0865]

Hey everyone, I am kind of lost with identifying my cases. I bought this engine on eBay and the guy said it was a '76 cb750f. I know the 76 f's and the 78 k's are almost identical, but when I try to match up the numbers I cannot figure out which one it is. I have it all in pieces for a complete rebuild and I would like to get it strait before I learn the hard way.

[ekpent]

Hey everyone, I am kind of lost with identifying my cases. I bought this engine on eBay and the guy said it was a '76 cb750f. I know the 76 f's and the 78 k's are almost identical, but when I try to match up the numbers I cannot figure out which one it is. I have it all in pieces for a complete rebuild and I would like to get it strait before I learn the hard way.

Here is another popular chart. Yours looks to be a K8      http://www.hondachopper.com/engine/engine_timeline/timeline.html

[bryanj]

According to the US Honda ID book i have the only engines starting  with a 3 are 1978 K8 models

1976 F starts at 2515
1972 K2 starts 2000
1970/71 K1 starts104
1969/70 K0 starts 1000

[754]

Is that case an sohc ? Number pad looks very far ahead..
 Ah i see it now its the late ones with the number boss nearer to the middle and turned 90degrees.i have only seen a few of those and I think the front motor mount is separate, on left side and comes off..

[Jonny0865]

754 it is a sohc. I could never really get any exact answer because I read that honda took 76f motors and began to use them for 78k motors but I'm not sure how interchangeable the parts are. Should I look specifically for 78k? Thanks guys

[Jonny0865]

Also, I checked the pistons (slight dome) and they are all stamped 392. I checked cmsnl and it says CB750F.1.P. Now this is really making me wonder. I know this engine is stock but can the case be a 78k but the pistons and head/can are from the 76f?

[ekpent]

1978 K model 750 uses a 392 piston also---3101-392-020

[Jonny0865]

Safe to say it's a 78k.... Thank you ekpent! Are there other ways to id a motor besides SN and piston number?

[754]

Used motor could have things changed, just got to go over stuff, and check.

[Jonny0865]

That is true. I just have to go piece by piece. This is my first rebuild so I don't wanna make any mistakes and have it cost me down the line. I appreciate all the help