Topic: CB750E What the heck does that mean?

[John G]

I'm not sure what motor I have. Can someone tell me where I can find information on this engine? Like year, 750k 750 K5 750 KE I'm confused. I have parts and maintenance manuals but nothing on what this motor number means. Help. Thanks

[Shtonecb500]

the E is normal and on every K motor I believe.

here you go
https://www.vintagecb750.com/model-guide-cb750

[grcamna2]

I was thinking the CB750E ****** engine number stamped into the cases:that the 'E' stood for 'Engine'.

The different model/year Honda engines have prefix numbers/letters(designating model and other info & identifications)ending with E just before the - and then the actual engine number.

[John G]

Interesting. E likely stands for engine. How do I know if this is the correct engine for my bike which is a 1975 according to the frame.

[Nurse Julie]

E stands for engine. Tell us your engine number and we can tell you if it's correct for a 75 frame. Also post a photo of the bike if you can.

[dave500]

FYI engine numbers and frame numbers are never the same on these old Hondas.

[PeWe]

Another link for numbers and years.
http://www.hondachopper.com/engine/engine_timeline/timeline.html

[John G]

Engine number is CB750E-2514530.
I think it's called a CB750K5

[newday777]

Engine number is CB750E-2514530.
I think it's called a CB750K5

That 2514530 engine numbers are more likely a K6 motor according to the chart above.
Engine numbers don't match the frame numbers.

What's your frame plate show for serial numbers and date of manufacture?

Your paint is a repaint for the K5 color, but the decal wasn't put on correctly.

My K5 has original paint and stripe so you can see the difference yours shows.

[John G]

Here's the frame info.

[Don R]

 It's a K5 frame but the engine numbers indicate F0 or F1. It probably came that way. 75/76 was a free for all in the factory engine wise. Hondaman reported F and K parts intermixed on the same engine. I recently put a 25XXXXX series engine in an F1 where a 76 K motor was. There was a plan to drop the K in favor of the F but buyers were saying they still wanted K's also.
 Even the chart says an early F engine may contain F or E in the serial number. I think it could have gone either way since Honda was doing whatever was necessary to build bikes. Even a known F engines head may not have the 392 cast into the top of it. 
 All the above is my opinion, your results may vary. L0L.

[rocket johnny]

nice looking set of pipes !

[John G]

Thanks very much Guys. I needed a cam as the cam that came with the bike was a new race cam with high performance valve springs and performance shims. I just wanted a nice running motorcycle to use on sunny days. Relive the younger days. Haha. I bought a cam from a motorcycle used parts place only to find out it's a 750 cam but for a Hondamatic according to the dimensions I get. If anyone has an idea what I would be up against with a high-performance motor for street use I'd love to hear from you as it seems a waist to have these new parts and not use them.

[jlh3rd]

Thanks very much Guys. I needed a cam as the cam that came with the bike was a new race cam with high performance valve springs and performance shims. I just wanted a nice running motorcycle to use on sunny days. Relive the younger days. Haha. I bought a cam from a motorcycle used parts place only to find out it's a 750 cam but for a Hondamatic according to the dimensions I get. If anyone has an idea what I would be up against with a high-performance motor for street use I'd love to hear from you as it seems a waist to have these new parts and not use them.

according to the official American Honda identification guide
you have a

cb750K 1976 engine in a..
cb750K5 frame (1975)

the 750 "F" model engine #'s start with cb750FE...

[Jerry Rxman Griffin aka MuthaF'er]

jlh3rd, that is incorrect information. They do NOT start with CB750FE. There MAY have been a few exports that were FE but I wouldn't even bet on that. Both of my 75 F's are good ole CB750E-250xxxx and as far as I know ALL 75/76 US F's begin with CB750E-250xxxx at least according to my American Honda Parts Manual. Note that these engines have one less digit in the number than other 750's. 

CB750E-2514530 would be a late 1975 CB750F0 which left off where the 76's started ie whereas the 76 F started with CB750E-2515094 to approximately CB750E-2554xxx.

You have a 1975 CB750F engine. The only stock cam that is really hotter than that is the 77/78 CB750F2 or F3 which are slightly hotter. Basically in their timing and duration and not lift. The early 69/70 and maybe 71 cams were also hotter. The mid year K's had detuned cams. Your WebCam is probably not as hot as the F cam but it's lobes are new and not worn.

If in doubt send me your phone number and I will text you the parts manual page in question.   

 

[jlh3rd]

I'm just showing  what Honda says, MuthaF'er.  I said "according to". Any alleged mistake is on them. Don't kill the messenger.
And the '76 K motor? Why couldn't it be a K? Someone else posted that before I did...didn't see you react to that...
And I count 7 digits in both engine model #'s.....you have 6 ?

all things considered it doesn't matter, right? The engines are the same...Except that the OP asked, so I answered....

and I know where an org.'75 F is, in an original Honda dealership.....pic.coming monday unless he's there today...

official Honda material can have erroneous info, as can any other sources. So I know that about this guidebook. But I go to it first anyway...

[Don R]

  My opinion is Honda was building as many bikes as possible and if there was a momentary shortage of anything, they would assemble what was on hand. Production was more important than technicalities. I can't imagine a supervisor stopping the assembly line for more than a few seconds.
  Evidence being the mixed K1/K2 parts, the French sandcasts in the 14K number range, the occasional known unmolested bike with a large number spread between frame and engine, they had no idea or worry about us, 50 years later comparing numbers.

[Jerry Rxman Griffin aka MuthaF'er]

jlh3rd, don't get your shorts in a bind.  It's not personal.  And I've been wrong before and have been called out.....  We are all just trying to help

I'm an original owner F guy that bought the bike in the first few weeks after they hit our shores. I have 6 or 7 reference books and, yes, the references differ. Agreed. However the engines are not all the same. Many changes throughout the 9 years.

I am seriously looking forward to seeing the original F !! I can't get enough of them. My holy grail. Please post it up. Thanks.

I figured out how to get the Honda parts book info. As can be seen this is from the 75 book so there are subsequent books out there that have been updated. Anyone, please take this only for what you see. 

What Don says has a lot of credence to it. Another option considering the repaint and perhaps more changes is that someone simply put a F engine into a K bike as they were doing work to it.


   

 

[69cb750]

Engines with 251 prefix came in F models, some examples -
CB750F-1011144 Build  2/75 CB750E-2511164
CB750F-1013366 Build  3/75 CB750E-2511164
CB750F-1014162 Build  3/75 CB750E-2514267
CB750F-2002124 Build  4/75 CB750E-2517100
CB750F-2008928 Build  ?/75 CB750E-2513465

No records of K models with 251 prefix engines.

[jlh3rd]

jlh3rd, don't get your shorts in a bind.  It's not personal.  And I've been wrong before and have been called out.....  We are all just trying to help

I'm an original owner F guy that bought the bike in the first few weeks after they hit our shores. I have 6 or 7 reference books and, yes, the references differ. Agreed. However the engines are not all the same. Many changes throughout the 9 years.

I am seriously looking forward to seeing the original F !! I can't get enough of them. My holy grail. Please post it up. Thanks.

I figured out how to get the Honda parts book info. As can be seen this is from the 75 book so there are subsequent books out there that have been updated. Anyone, please take this only for what you see. 

What Don says has a lot of credence to it. Another option considering the repaint and perhaps more changes is that someone simply put a F engine into a K bike as they were doing work to it.


   

great....
Since I'm into originality and whats correct, I enjoy, sometimes, the investigation process in trying to determine what is fact or opinion......it's a minefield...and Honda doesn't make it easy......
....this 750 "F" engine # thing popped up here before.....actually, I don't think they are stamped with an "F", but that would be conjecture on my part which is why I said according to honda.
....this is the bike....should be open tomorrow.....missing the original exhaust, of course....
edit...and a "gold wing" bar across the uppers?

[jlh3rd]

Engines with 251 prefix came in F models, some examples -
CB750F-1011144 Build  2/75 CB750E-2511164
CB750F-1013366 Build  3/75 CB750E-2511164
CB750F-1014162 Build  3/75 CB750E-2514267
CB750F-2002124 Build  4/75 CB750E-2517100
CB750F-2008928 Build  ?/75 CB750E-2513465

No records of K models with 251 prefix engines.

vearing from the Op.....so no 750 K6 engine has a 251.... #?
also...posted in here before....there is some kinda weird production run with the '75 F's and '76's in that the '75's were only made for 2 months ...4 months?...something like that....

[Don R]

 Yes, F0 only was made until April when Honda lost a class action lawsuit in New York for re-titling left over bikes to the next year. That's when they went right into 1976 production. You might notice the rarity of 1975 compared to 1976 bikes. 

[Jerry Rxman Griffin aka MuthaF'er]

Engines with 251 prefix came in F models, some examples -
CB750F-1011144 Build  2/75 CB750E-2511164
CB750F-1013366 Build  3/75 CB750E-2511164
CB750F-1014162 Build  3/75 CB750E-2514267
CB750F-2002124 Build  4/75 CB750E-2517100
CB750F-2008928 Build  ?/75 CB750E-2513465

No records of K models with 251 prefix engines.

vearing from the Op.....so no 750 K6 engine has a 251.... #?
also...posted in here before....there is some kinda weird production run with the '75 F's and '76's in that the '75's were only made for 2 months ...4 months?...something like that....

That's an earlier 75 too as witnessed by the nylon cup rear master cylinder. Looks good from that shot.

[jlh3rd]

its for sale...

[PeWe]

The variants continue in Europe
CB750 K2 was delivered here to 1975. No K3-K5.

K6 from 1976 as my avatar bike that arrived early fall 1976, registered as a 1977 which gave me problems when order things back in 1979-80 until I figured it out.

K2 bikes have K2 frame numbers. Engines like the US models for the actual year.

A 1975 K2 has 1975 engine numbers and built like one too. Later head and cylinder.

K2 gauges during all years.
The 1972 K2's look older with the earlier head.

Blinkers, rear light with fender like K1 but still different.
It has more holes for the mudflap that was a must here at each annual vehicle inspection, plus an approved reflex with correct E number.
This continued on K6 too.

One single grab bar on left side for all K2