Author Topic: Newbie question about my CB 750 motor? (Read 3139 times)

Dogma270 · « **on:** June 02, 2020, 11:12:43 AM »

I just recently picked up 2 1975? CB 750s. I found this as probably the best place for help as I attempt to put them both together into one functional bike. One of them is a K5 motor, but the other one has been more difficult to ID. Any help to identify it would be most appreciated as I decide which motor to use and decide if parts are interchangeable. The motor ID starts with a small "cL" then has 750 and the 7 digit number. I can't find this any where and wondered if it tampered with? Thanks for any help you can give. Photo attached

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Stev-o · « **Reply #1 on:** June 02, 2020, 03:00:01 PM »

The cl is not standard and that is not a valid engine number! It should start with "CB750E-" then the sequential production number. Does the 3036214 match the frame number? Or the title??

303 would be 1978, last year of the SOHC.

Good luck with that!

Dogma270 · « **Reply #2 on:** June 02, 2020, 04:34:06 PM »

I know. The other motor starts with CB750E from 75. Alabama doesn't title bikes that old and I can't read the frame VIN. Was told it was a "748 short stroke". The 0 looks like it was double struck. The 4 certainly looks accurate according to the other motor.

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seanbarney41 · « **Reply #3 on:** June 02, 2020, 04:36:53 PM »

All cb750 sohc are "short stroke " ...736cc

Dogma270 · « **Reply #4 on:** June 02, 2020, 04:37:33 PM »

Actually, now that I look at the picture, the none of the numbers seem to match up with the font/style of the other one?

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Dogma270 · « **Reply #5 on:** June 02, 2020, 04:38:48 PM »

I had read that, but weren't some later ones 748cc? Or could it be stroked/overbored?

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Dogma270 · « **Reply #6 on:** June 02, 2020, 04:40:11 PM »

Everything else appears to be identical to the other CB 750 motor I have.

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seanbarney41 · « **Reply #7 on:** June 02, 2020, 04:50:41 PM »

Most certainly was some sort of diy case stamp. Likely the cases needed replacement at some point in history die to chain or other damage. Blank cases were available from honda back in the day. Many were left unstamped.

scottly · « **Reply #8 on:** June 02, 2020, 07:45:16 PM »

Take a picture of the front sprocket on the mystery motor; '77 and up motors are different in that area than earlier motors.

bryanj · « **Reply #9 on:** June 02, 2020, 10:58:07 PM »

Replacement cases and whoever did it stamped it wrong

Stev-o · « **Reply #10 on:** June 03, 2020, 07:01:08 AM »

Quote from: Dogma270 on June 02, 2020, 04:38:48 PM

I had read that, but weren't some later ones 748cc?

Or could it be stroked/overbored?

No. Highly doubt it. I never believe a seller!

pmanning · « **Reply #11 on:** June 03, 2020, 07:50:06 AM »

Alabama became a title state in 1975. I know this because the bike I ride today I bought salvage from a shop in Birmingham in 1977. Serial numbers from the frame and engine identify it solidly in the K5 range or 1975 production year. The shop did not have the title for the bike so the salesman wrote up the bill of sale as 1974 so I could get it licensed in Alabama without applying for a new title. (I hope none. of the authorities read this.) When I moved to Texas in 1980 a title was required and the title I received identifies it as a 1974 model. I now live in Washington state and it is titled here as a '74 model.

Things involving vehicle licensing were played pretty fast and loose when I lived there in the '70s. It is a pretty good bet the cases you have with the odd number were replacement cases resulting from a chain failure. That was pretty common in the day. You may never resolve the mystery behind the selection of the number on those cases. "CL" was Honda's dirt bike classification. The other numbers might be the mechanic's girlfriends telephone number.

carnivorous chicken · « **Reply #12 on:** June 03, 2020, 08:04:55 AM »

Quote from: seanbarney41 on June 02, 2020, 04:50:41 PM

Most certainly was some sort of diy case stamp. Likely the cases needed replacement at some point in history die to chain or other damage. Blank cases were available from honda back in the day. Many were left unstamped.

This, although I'm intrigued. CL? Maybe someone thought they would fit it with high pipes!

Jerry Rxman Griffin aka MuthaF'er · « **Reply #13 on:** June 03, 2020, 09:30:17 AM »

Quote from: Dogma270 on June 02, 2020, 04:38:48 PM

I had read that, but weren't some later ones 748cc? Or could it be stroked/overbored?

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Didn't happen. Don't believe everything people say.

Alan F. · « **Reply #14 on:** June 03, 2020, 09:35:44 AM »

Never trust Wikipedia.

https://en.m.wikipedia.org/wiki/Honda_CB750#Specifications

Dogma270 · « **Reply #15 on:** June 03, 2020, 09:39:53 AM »

Here is the front sproket. It is stamped 1908 if that means anything?

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Dogma270 · « **Reply #16 on:** June 03, 2020, 09:41:18 AM »

Quote from: Alan F. on June 03, 2020, 09:35:44 AM

Never trust Wikipedia.

https://en.m.wikipedia.org/wiki/Honda_CB750#Specifications

That's why I am asking here. The PO swore it was a 748cc. He owned them for 15 years. They have been in a barn for the last 7.

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754 · « **Reply #17 on:** June 03, 2020, 09:47:18 AM »

Ok that is a 76 or earlier lower end.
Post a pic of the outer end of the cylinder heads or the front top head fin, and we can tell you if the head is 73 and or later.
By this stage in time, a lot of parts have been switched.
How are the engine covers corrosion wise ? Good cylinder and head fins..?

Dogma270 · « **Reply #18 on:** June 03, 2020, 09:54:13 AM »

Also, these look like original gauges from what I can tell? What do you think? Also, are these forks factory?

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Dogma270 · « **Reply #19 on:** June 03, 2020, 09:56:51 AM »

Quote from: 754 on June 03, 2020, 09:47:18 AM

Ok that is a 76 or earlier lower end.
Post a pic of the outer end of the cylinder heads or the front top head fin, and we can tell you if the head is 73 and or later.
By this stage in time, a lot of parts have been switched.
How are the engine covers corrosion wise ? Good cylinder and head fins..?

No damage that I can see.

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Dogma270 · « **Reply #20 on:** June 03, 2020, 10:02:39 AM »

One frame is 73 (2227277) the other is a 75? (2505826).

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754 · « **Reply #21 on:** June 03, 2020, 10:04:01 AM »

That is a 72 or earlier head a few early 73 had them. It has Been changed to stud mount a later head thing.
The orange fender fork, might be Goldwing 37 mm. The blue bike gas a kawi front wheel.and forks.
The first tach you showed , if it has 2 studs on back is 73 or later , the other tach off smaller honda

Dogma270 · « **Reply #22 on:** June 03, 2020, 10:26:57 AM »

Quote from: 754 on June 03, 2020, 10:04:01 AM

That is a 72 or earlier head a few early 73 had them. It has Been changed to stud mount a later head thing.
The orange fender fork, might be Goldwing 37 mm. The blue bike gas a kawi front wheel.and forks.
The first tach you showed , if it has 2 studs on back is 73 or later , the other tach off smaller honda

It turns over just fine. Would it be worth building or sell it. If sell it, how much are they worth? Thanks again.

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754 · « **Reply #23 on:** June 03, 2020, 10:34:32 AM »

Show a side view of the bikes, what tank, wheels seats, etc.,
Values depend a lot on supply and demand where you live.
And you have a real mix of parts. No problen0m to build a bike and have fun with it, but to sell you you don't have say a fairly complete 74 or76 or like that.

Dogma270 · « **Reply #24 on:** June 03, 2020, 10:46:33 AM »

Quote from: 754 on June 03, 2020, 10:34:32 AM

Show a side view of the bikes, what tank, wheels seats, etc.,
Values depend a lot on supply and demand where you live.
And you have a real mix of parts. No problen0m to build a bike and have fun with it, but to sell you you don't have say a fairly complete 74 or76 or like that.

Momma is saying no to building a bike. I figured since I have such a mixed bag of parts, I might be able to part them out and do a little better? I live in Alabama so, lots of country do it yourselfers around here.

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Author Topic: Newbie question about my CB 750 motor? (Read 3139 times)