Author Topic: 1969-70 CB750E Engine? SOLVED! (Read 8205 times)

Yamahawk · « **on:** February 15, 2018, 06:03:25 PM »

Found this engine sitting out back of my friend Pat's shop. According to the Hondachopper site, this should be either a 1969 or 1970 engine, is this correct? It also has the chain guard update for the early engines to protect against chain breaking the case ahead of the front sprocket.
Charlie

danyo · « **Reply #1 on:** February 15, 2018, 06:22:43 PM »

It's a 1970 engine. Probably cases were replaced - font is not original honda.

Sent from my SM-N900T using Tapatalk

setdog · « **Reply #2 on:** February 15, 2018, 06:25:16 PM »

i recently found a frame 103xxxx with a production date 4/70, i would say thats a K0 engine.

Yamahawk · « **Reply #3 on:** February 15, 2018, 06:43:25 PM »

Quote from: danyo on February 15, 2018, 06:22:43 PM

It's a 1970 engine. Probably cases were replaced - font is not original honda.

Sent from my SM-N900T using Tapatalk

I think I see what you mean about the font, I took another picture of a later engine, and the serial number was at a different location, think its a 1978 CB750K, and the font has the taller '5' and you can tell the difference.
Charlie

Yamahawk · « **Reply #4 on:** February 15, 2018, 06:45:52 PM »

Quote from: danyo on February 15, 2018, 06:22:43 PM

It's a 1970 engine. Probably cases were replaced - font is not original honda.

Sent from my SM-N900T using Tapatalk

Would that mean it was replaced under warranty, and they stamped the new cases with the original serial number? It might be why they retrofitted the front chain guard to prevent case breakage from a snapped chain!
Charlie

754 · « **Reply #5 on:** February 15, 2018, 06:50:07 PM »

Yamahawk, you won't see many with the serial number turned like that on 750 sohc.
They also had a different front motor mount.

danyo · « **Reply #6 on:** February 15, 2018, 07:00:26 PM »

I believe only k8 engines have numbers turned 90 deg, correct??

Sent from my SM-N900T using Tapatalk

Yamahawk · « **Reply #7 on:** February 15, 2018, 07:02:05 PM »

Quote from: 754 on February 15, 2018, 06:50:07 PM

Yamahawk, you won't see many with the serial number turned like that on 750 sohc.
They also had a different front motor mount.

Frank,
Does that mean the 2nd picture is of a last run of the CB750 SOHC engine, perhaps a late 1978?
What do you think about the K0 engine, it has a different font than the rt. angle stamped later model...
Charlie

Stev-o · « **Reply #8 on:** February 15, 2018, 07:07:34 PM »

Quote from: danyo on February 15, 2018, 07:00:26 PM

I believe only k8 engines have numbers turned 90 deg, correct??

My current project has a K8 motor but numbers are not like that

754 · « **Reply #9 on:** February 15, 2018, 09:40:49 PM »

I think some of the K8, i have only seen a few. They may be late ones but I am not sure.
I didn't look at the font, but noticed the numbers are a bit wavy, I think always straight at the factory as they would be in a holder of some sort.

Yamahawk · « **Reply #10 on:** February 16, 2018, 01:59:04 AM »

I'll check my '71 font it is a 107xxxxxx #... post later!
Charlie

magnum56 · « **Reply #11 on:** February 16, 2018, 08:03:55 AM »

Here is my engine number ... dirty before my rebuild last year.
The font is quite wavy and it's been welded up nicely where the chain took it out at some point.

Yamahawk · « **Reply #12 on:** February 16, 2018, 01:55:08 PM »

This is my 1971 engine #...
The font looks like Honda, with the '5' being tall through the place above the curve.

Charlie

BPellerine · « **Reply #13 on:** February 16, 2018, 02:30:37 PM »

I have a 78 with the numbers at 90 degrees.bill

754 · « **Reply #14 on:** February 16, 2018, 04:11:02 PM »

Ok compare your number with the one shown.
And is there one or two removeable front motor mounts.?

BPellerine · « **Reply #15 on:** February 17, 2018, 10:13:22 AM »

Quote from: 754 on February 16, 2018, 04:11:02 PM

Ok compare your number with the one shown.
And is there one or two removeable front motor mounts.?

same mounts as any other sohc,the rear is diff on 78

Stev-o · « **Reply #16 on:** February 17, 2018, 11:33:23 AM »

Quote from: BPellerine on February 17, 2018, 10:13:22 AM

Quote from: 754 on February 16, 2018, 04:11:02 PM
Ok compare your number with the one shown.
And is there one or two removeable front motor mounts.?
same mounts as any other sohc,the rear is diff on 78

Hey Bill...what is diff? I'll be soon mounting a K8 motor in a K5, anything I need to know?

BPellerine · « **Reply #17 on:** February 18, 2018, 06:52:25 AM »

steve,the actual mount,or mounting plate mounts on the outside of the frame on 78,but I think the earlier mount works too,the only thing you will have to worry about is chain alignment.bill

Stev-o · « **Reply #18 on:** February 18, 2018, 12:58:32 PM »

Quote from: BPellerine on February 18, 2018, 06:52:25 AM

steve,the actual mount,or mounting plate mounts on the outside of the frame on 78,but I think the earlier mount works too,the only thing you will have to worry about is chain alignment.bill

Hey Bill...thanks. Yes, am aware of the chain alignment issue, I have a K7 sprocket carrier....

Terry in Australia · « **Reply #19 on:** February 18, 2018, 04:17:40 PM »

Charlie, those K0 cases are re-stamped warranty cases. I've got an unstamped set here. They must have been pretty common on early CB750's, I've seen heaps of them. Sadly they substantially lower the value of a bike, or an engine. Cheers, Terry.

Yamahawk · « **Reply #20 on:** February 18, 2018, 06:38:42 PM »

Quote from: Terry in Australia on February 18, 2018, 04:17:40 PM

Charlie, those K0 cases are re-stamped warranty cases. I've got an unstamped set here. They must have been pretty common on early CB750's, I've seen heaps of them. Sadly they substantially lower the value of a bike, or an engine. Cheers, Terry.

Hi Terry,
You know, that's what I figured after I saw the stamp wasn't the stock numerical font... And, the addition of the chain guard for the front sprocket area, to stop the case from breaking... It's a shame they aren't worth as much as the case they replaced, as they were probably within a year or two from new when the chain took out the case. Oh well, at least its got a low serial #...
Charlie

HondaMan · « **Reply #21 on:** February 18, 2018, 07:27:50 PM »

When we had to replace broken cases in those days...Honda required the serial number be re-stamped on it, with some additional punch marks to indicate it wasn't OEM.

...but a lot of them didn't get stamped, because no one had the stamps...

Terry in Australia · « **Reply #22 on:** February 18, 2018, 07:30:02 PM »

Yeah mate, I saw one poor bugger who thought he got a bargain when he bought a sandcast, only to find that it had replacement cases, so was technically a "Bitsa". If he still had the sandcast cases and was able to repair them, his bike would have doubled in value.

The trouble with replacement cases is if you find an unstamped set like mine, you can stamp any number you like on them.

Oooooher, that's given me an idea, anyone wanna buy my (very rare) K0 engine? Serial number CB750E-10000001, I just found it, er, in a barn.........

Don R · « **Reply #23 on:** February 18, 2018, 07:43:30 PM »

I have an unstamped early replacement case for my 14,100 vin bike. I'd love to know how to read the hex stamped date codes to see how old it is. It came with the original no center bolt head and cylinder.

Terry in Australia · « **Reply #24 on:** February 18, 2018, 09:50:08 PM »

Looking at the amount of K0's that I've seen with welded cases Don, I'd just about assume that yours was a K0 that was chain damaged back in the day, but unless you have documentation from the dealer who did it, how will you ever know for sure? Like Mark said, some of the dealers didn't even have stamps, which is probably how I ended up with a set of unstamped cases.

Terry's Unstamped Cases by terry prendergast, on Flickr

News:

Author Topic: 1969-70 CB750E Engine? SOLVED! (Read 8205 times)