Author Topic: 1972 Honda cb750 K2 engine serial numbers (Read 11119 times)

guitarkev66 · « **on:** January 07, 2015, 08:10:24 AM »

I have a 11/71 cb750 K2 frame serial number 2004090 its engine number is 2011818 thats over 7000 different from the frame. I know that the numbers never match but the K1's I have and had were all within a few hundred from each other. Another member has an early K2 built 11/71 with frame number 2004896 with engine number 2012601 which again is over 7000 apart. With these two bikes being so early in the k2 production with frame and engine numbers being so far apart it doesn't make much sense, what happened to the 7000 engines? Mark Paris told me a few years ago that the first 4000 K2's went to the Japan market, that would make my bike #90 brought to the U.S. in late 1971. I am just curious to here from you K2 owners to see if your bikes have the same number difference. Or from Honda techs from the 70's to here your explanations.

edwardmorris · « **Reply #1 on:** January 07, 2015, 10:43:03 AM »

Mine's a 11/71 K2 with a 7K diff on the numbers, seems pretty consistent. Early K2s have a lot of oddities, IMHO to get these restored right is as bad as restoring a sandcast (or worse as the odd K2s are fewer in number than sandcasts and not many survived).

David B · « **Reply #2 on:** January 07, 2015, 01:55:05 PM »

Any insight HondaMan?

goldarrow · « **Reply #3 on:** January 07, 2015, 02:20:28 PM »

Quote from: guitarkev66 on January 07, 2015, 08:10:24 AM

Mark Paris told me a few years ago that the first 4000 K2's went to the Japan market, that would make my bike #90 brought to the U.S. in late 1971. I am just curious to here from you K2 owners to see if your bikes have the same number difference. Or from Honda techs from the 70's to here your explanations.

if the first 4000 K2's went to Japanese market, i would like to see where this number came from, as it is contradicting to what i have. my K2 is a JDM and frame serial suggests differently. Engine numbers is from K3, this seem to imply something about the K3 model year is missing from Japan market

guitarkev66 · « **Reply #4 on:** January 07, 2015, 02:37:43 PM »

Quote from: goldarrow on January 07, 2015, 02:20:28 PM

Quote from: guitarkev66 on January 07, 2015, 08:10:24 AM
Mark Paris told me a few years ago that the first 4000 K2's went to the Japan market, that would make my bike #90 brought to the U.S. in late 1971. I am just curious to here from you K2 owners to see if your bikes have the same number difference. Or from Honda techs from the 70's to here your explanations.

if the first 4000 K2's went to Japanese market, i would like to see where this number came from, as it is contradicting to what i have. my K2 is a JDM and frame serial suggests differently. Engine numbers is from K3, this seem to imply something about the K3 model year is missing from Japan market

Not sure where Mark got this info about the first 4000? I always thought JDM models were always at the tail end of production as with my K0 jdm. What are your frame and engine numbers? I am real interested to figure this mystery out. I'm hoping someone on the forum has a K2 with a 200xxx engine number or even a lower frame number than mine.

goldarrow · « **Reply #5 on:** January 07, 2015, 03:38:12 PM »

my K2 JDM frame is 2083xxx, engine is 2253xxx

guitarkev66 · « **Reply #6 on:** January 07, 2015, 04:11:11 PM »

Wow your 17000 different.... Do you believe the engine to be original to the bike? What differences did the K2 JDM's have from the U.S. bikes? Do you have pictures of it? Where did you find it? Is it all original?

jerry h · « **Reply #7 on:** January 07, 2015, 07:13:58 PM »

Same thing here.... 2/72 - 7892 number difference between frame and engine.

guitarkev66 · « **Reply #8 on:** January 08, 2015, 06:57:36 AM »

Okay here is what I am thinking and please correct me if this sounds wrong. Production of the K2 bikes probably started around 10/71 to be safe, with frame #2,000,000 and engine #e2,000,000. By mid month 11/71 they would've produced my bike with frame #2,004,090 which would equal about 4,090 bikes in a month of production. Here is where things get confusing to me, If it takes them one month to put together roughly 4,000 bikes how could they have assembled 11,818 engines in such a short time unless they had a stock pile of engines leftover from earlier year.(which makes sense why Mark Paris said his motor was a reworked K1). I got 11,818 from my engine #2,011,818. And if they had a stock pile of engines what frame # bikes would've received say engine number 2,004,090 just for reference? The numbers just are not adding up other than with all our k2's frame #'s and engine#'s being about 7,000 off. There has to be an explanation for this.

seanbarney41 · « **Reply #9 on:** January 08, 2015, 01:31:02 PM »

This is just a guess. Didn't production at the original factory end during K2 production? Maybe something about switching from the old factory to the new caused a numbering glitch...

guitarkev66 · « **Reply #10 on:** January 08, 2015, 02:46:18 PM »

Quote from: seanbarney41 on January 08, 2015, 01:31:02 PM

This is just a guess. Didn't production at the original factory end during K2 production? Maybe something about switching from the old factory to the new caused a numbering glitch...

Good answer... Not really sure when the change of factories took place?? That might be a possibility though. Thanks...

trigger · « **Reply #11 on:** January 09, 2015, 09:28:17 AM »

1 in every 100 engine's was pulled for testing the BHP output. Frames were made a lot quicker than the engines. Movement of factory's means it is not uncommon to see numbers this far apart.

guitarkev66 · « **Reply #12 on:** January 09, 2015, 06:09:42 PM »

On all my pre K2 motorcycles the engine number is lower than the frame by a few hundred and I have had six pre K2 cb750's. So That makes sense for those bikes with the frame number higher than the engine. But these K2 bikes in question have the motor number 7000 over the frame so even If 1 out of 100 motors were pulled by my bike 2,004,090there would've been roughly 41 motors pulled. I am still thinking Honda for some reason didn't start the K2 engine numbers @2,000,000 but around 2,007,000. Not sure why. This is why I am hoping someone has a K2 with a low 2,000,000 engine number so my idea is disproved. I am waiting to hear back from Mark Paris on what his engine number is, I believe he may have a low 2,000,000 engine serial number. Thank you for your theory trigger... Keep'em coming, I would really like to figure this out.

edwardmorris · « **Reply #13 on:** January 09, 2015, 10:22:10 PM »

IINM Mark's is one of the first 800 K2s ever made, rarest batch that had K1 style gauges (AND the K2 style dash??) and for all intents and purpose a K1 engine. I hope he stops by here soon, I'm kinda curious now..

guitarkev66 · « **Reply #14 on:** January 10, 2015, 06:46:13 AM »

K1 style gauges? Thats real interesting I would love to see some pictures . Would they have the dummy lights in the gauges and a on the dash?

atm cycles · « **Reply #15 on:** January 10, 2015, 12:14:08 PM »

I think David B k2 is within 30 numbers of hondamans. My k2 numbers are 7705 apart

edwardmorris · « **Reply #16 on:** January 10, 2015, 01:12:57 PM »

Quote from: guitarkev66 on January 10, 2015, 06:46:13 AM

K1 style gauges? Thats real interesting I would love to see some pictures . Would they have the dummy lights in the gauges and a on the dash?

I believe so. The only other place I've seen those is on a race 750, either Seely or one of the other legendary versions of the time.

guitarkev66 · « **Reply #17 on:** January 10, 2015, 05:58:23 PM »

I guess my real curiosity lies with my K2, it being lower serial number than Hondamans if my motor is original to my bike. Which if everyones K2 is around 7000 of I would think Hondamans should be too. Hondamans K2 frame is 2,004,850 I think? Mine is 2,004,090

guitarkev66 · « **Reply #18 on:** January 15, 2015, 09:35:54 AM »

Okay, Mark Paris got back to me about his early K2 engine number. It is 2012242 which falls into the 7000 number gap between frame and engine numbers. My frame and his are 440 numbers apart my engine and his are 424 apart which lines up correctly if you take into account the 1 in 10 engines removed for testing. Which makes my original idea that Honda started the run of K2 engine numbers at around 2007000 and not at 2000000 like specified by honda. Still hoping to find a low 2000000 engine number out there. i plan on figuring this number deal out so if anyone has any info or memory of this topic please help.... thanks

edwardmorris · « **Reply #19 on:** January 15, 2015, 12:14:18 PM »

Gotta love the K2, joyfully painful

754 · « **Reply #20 on:** January 15, 2015, 03:06:02 PM »

I checked two today, but higher numbers..close together tho 23,716 and 23,937.
And I discovered I had not just one set of blank cases,but looks like two or three..

guitarkev66 · « **Reply #21 on:** January 15, 2015, 05:56:37 PM »

Interesting 754, I would've figured the later K2's being even further apart on the number spread...

754 · « **Reply #22 on:** January 15, 2015, 07:45:02 PM »

It was not the bike, it was 2 engines, one which I bought in 74, cases are unusable..except for display

trigger · « **Reply #23 on:** January 17, 2015, 03:16:45 PM »

I would like to throw a bit of confusion in to this numbers game.
In the UK we never had K3, K4 or K5. It just stayed at K2 so even if you have a 1974 CB750 in the UK the frame number sill started with 20...... but, the engine numbers carried on as they did in the USA.
I have 3 CB750K2's at the moment and here is a example of the way the numbers went
1972 CB750K2, Frame number CB750-2050308 with engine number CB750E-2058045
1974 CB750K2, Frame number CB750-2084102 with engine number CB750E-2256216
1975 CB750K2, Frame number CB750-2086882 with engine number CB750E-2307782
I have also just sold a 1972 K2 with the engine number lower than the frame.

Don R · « **Reply #24 on:** October 02, 2016, 11:53:11 PM »

I'm dredging this old thread up, my K2 bike has the 1106464 engine, early forks, late gauges and light console. it also has a no number replacement frame. I'm wondering if it could really be a k1 due to the engine number. There is a sissy bar with the tail lights mounted on it so no grab bar or handle. I know it had a big bore kit put on and with the frame deal I'm wondering if it was a legit factory bike or a bike made out of parts after a wreck. It's always been called a k2 and the now lost title said it was a 72.

Old Moe Toe · « **Reply #25 on:** October 03, 2016, 12:50:53 AM »

Hi Don
The literature I have at hand says K1's started with engine number of 1044806 onwards until the K2's, which started with 2000001 onwards until the K3's.
According to that yours has a K1 engine.
Lucky you! I'd like a K1 engine.
Cheers

Don R · « **Reply #26 on:** October 03, 2016, 07:46:39 AM »

I know, that's what's strange, the bike shows all the signs of being a K2, I'm wondering if it's a transition bike and the engine was a holdover for repairs or a one in a hundred that got dyno tested.

VTCBike750 · « **Reply #27 on:** January 02, 2020, 05:07:00 PM »

Digging up an old thread.

Just looked at a K2:
Frame 2002424, Engine 2010008

trigger · « **Reply #28 on:** January 02, 2020, 10:26:31 PM »

What about the CB750K2's that had frame/VIN numbers starting with 21***** These were sold in the UK in mid 1975 to early 1976

PeWe · « **Reply #29 on:** January 02, 2020, 10:33:21 PM »

Quote from: trigger on January 02, 2020, 10:26:31 PM

What about the CB750K2's that had frame/VIN numbers starting with 21***** These were sold in the UK in mid 1975 to early 1976

Sweden too. My K2 1975 has 21028xx.
I have full documentation from it was imported by Honda dealer asking for registration July 1975.

VTCBike750 · « **Reply #30 on:** January 03, 2020, 03:21:20 AM »

Quote from: guitarkev66 on January 10, 2015, 05:58:23 PM

I guess my real curiosity lies with my K2, it being lower serial number than Hondamans if my motor is original to my bike. Which if everyones K2 is around 7000 of I would think Hondamans should be too. Hondamans K2 frame is 2,004,850 I think? Mine is 2,004,090

Quote from: guitarkev66 on January 15, 2015, 09:35:54 AM

Okay, Mark Paris got back to me about his early K2 engine number. It is 2012242 which falls into the 7000 number gap between frame and engine numbers. My frame and his are 440 numbers apart my engine and his are 424 apart which lines up correctly if you take into account the 1 in 10 engines removed for testing. Which makes my original idea that Honda started the run of K2 engine numbers at around 2007000 and not at 2000000 like specified by honda. Still hoping to find a low 2000000 engine number out there. i plan on figuring this number deal out so if anyone has any info or memory of this topic please help.... thanks

Forgot to mention that it had a production date of 10/71, earliest Ive seen on a K2.
Frame 2002424, Engine 2010008, Lowest U.S. K2 Ive seen, online or in person.

K1 Engine with an early K2 Engine VIN?
http://www.sohc4.net/cb750k-serial-numbers

69cb750 · « **Reply #31 on:** January 03, 2020, 08:52:17 AM »

Quote

Forgot to mention that it had a production date of 10/71, earliest Ive seen on a K2.
Frame 2002424, Engine 2010008, Lowest U.S. K2 Ive seen, online or in person.

2002424 is #2424 K2
I have seen -
CB750-2001814 build 10/71 CB750E-200071x
CB750-2002436 Build 10/71 CB750E-2010165

Keith · « **Reply #32 on:** January 03, 2020, 04:10:02 PM »

My K2 is way off too. Mine is a 11/71 build, I will have to look at the numbers, but I know it is quite a bit off. Always wondered about that, since I had it since 4,000 miles on it.

Keith · « **Reply #33 on:** January 03, 2020, 04:28:58 PM »

My frame #2004208, my engine #2011833. So I am over 7,000 off too. Looks like an early K2 as well, mine has the red side cover emblems....anyone else?

69cb750 · « **Reply #34 on:** January 04, 2020, 05:32:53 AM »

Quote

My frame #2004208, my engine #2011833. So I am over 7,000 off too. Looks like an early K2 as well, mine has the red side cover emblems....anyone else?

11/71 build ?
K2's started aligned but quickly jumped to 7500 engine offset, no idea why.

CaptFatCat · « **Reply #35 on:** January 04, 2020, 07:41:39 AM »

My K2 is a 3/72 with 7,355 digits apart.. looks like the engine shop worked a little faster than the frame shop.

jlh3rd · « **Reply #36 on:** January 05, 2020, 05:40:18 AM »

Isn't the honda motorcycle identification guide and it's associated frame and engine numbers for american import bikes only? There is no identification guide for european bikes ? So doesn't this add to confusion ?
The identification guide is not error proof.
Isn't the data plate on the frame strictly the frame production date? My 75 550F, like some of your 750's , has a data plate of 12/74...but it's a 75, so the data plate date is somewhat irrelevant? It's the frame # that is relevant? But a motor vehicle registration department could title mine as a 1974 model.....more confusion.
If your frame has no data plate and all you have is the engine number, that number would be the only official " document " as proof of model year. Lots of parts from many years can be interchanged so that doesn't prove what model you have, nor does the title date, unless you are the original owner or have further documentation of the initial purchase.....

PeWe · « **Reply #37 on:** January 05, 2020, 07:53:18 AM »

The European bike looked different.
CB750 K2 sold between 1972- 75.
Same look 1975 as 1972 except for cylibder and head. K1 style blinkers, rear lamp and fender. Rhino horn mounted gauges and only one grab rail on left side.

K6 as US bikes except for blinkers, rear lamp and fender that still have K1 style. EU handlebar loer than US.

Headlight had H4 on all of the K2 and K6 as I have understood.

Rear fender not exactly as K1 that only had 1 hole for rubber mud flap. The Euro bike had 4 oval holes in rhe rear fender for the flap. I have a NOS K1 fender for my K6 as spare. The original version not to be found.

K3- K5 not sold here.

bryanj · « **Reply #38 on:** January 05, 2020, 03:23:56 PM »

A bike built in japan 12/74 is not going to be uncrated anywhere till 1975 and in UK it is the date of first rREGISTRATION that counts, alsoit would have been a 75 model anyaay

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Author Topic: 1972 Honda cb750 K2 engine serial numbers (Read 11119 times)