Topic: Strange engine numbers?

[Mycall1983]

My family have multiple 750 fours and parts, two of the engines have strange engine numbers. One is 750-2065*** (no CB in front) and the other is simply 075127P. We are located in Australia but it still doesn’t make sense to me?

Both are SOHC K models are far as I know.

[Nurse Julie]

Can you post a photo of the numbers and the bikes so we can see if they are original Honda Font and are K model CB SOHC 4'S.

[Mycall1983]

First one

[Mycall1983]

And second

[PeWe]

Replacement cases?

[Nurse Julie]

As PeWe says, probably replacement cases as not Honda Font.

[bryanj]

First one might be a police or official stamp on un numbered new cases, second looks like a dealer with no letter stamps.
New cases came unstamped, same as new parts frames

[Mycall1983]

Very interesting, very helpful and insightful 🤘🏻

[newday777]

I agree that they are most likely replaced cases that someone hand stamped. Unless you find the person/shop that did the change, you may never know the history of them. Many cases were replaced because of a busted drive chain that put a hole in the original cases.
Notice the uneven line of numbers. Factory stamping were done in straight line, probably with a type set to hold the numbers and letters straight.

[CycleRanger]

And second

As others mentioned, very likely a replacement case that was assembled by a dealer or a shop that only had number stamps.

[seanbarney41]

Agree that they have been re-stamped, probably replacement cases.  We can tell you they are not early K0(sandcasts) by the raised rectangle around the number pad.  There may be other visual cues which can narrow down roughly when these engines may have been made.  Some more good pictures may get us started.

[ZTatZAU]

... Many cases were replaced because of a busted drive chain that put a hole in the original cases.
...

Quick question!  I've owned my K1 750 since 1971 and seem to recall a Honda "recall" that installed a protective shoe or guard of some sort to protect the cases in the event of a broken chain.

But when I recently resurrected the bike after a thirty year hiatus, I was surprised NOT to see any sort of a add-on chain guard around the final drive sprocket.

I know I replaced the final drive sprocket, rear wheel sprocket and chain at some point in the distant past but don't remember dealing with any "extra device" that I might have pitched.

Can anyone post a picture of the Honda chain guard device?  Or did I dream all this up?

ZT

[Don R]

  Sorry for the thread hijack,
 Somewhere I have a picture of an engine that I bought that had parts of the drive chain inside the engine case, it had gotten between the transmission gears, damaged them and was spit through the circular hole cover and hanging out the bottom of the engine.
 I'll try to get a pic of an interior chain guard today. I have 10 750's (some are parts or drag bikes) and I don't think any have the guard in place.
 I'll get a pic of a blank engine number pad also.
 

[Stev-o]

And second

Does the engine number match the frame VIN or title?

[Don R]

 Here is a no stamp newer replacement engine case removed from a sandcast bike. It has the Sandcast's cylinder and head. It didn't get numbers but did get the three punches from the factory recall that addressed the chain breakage.

[bryanj]

Pic from CMSNL K2 parts list

[CycleRanger]

Pic from CMSNL K2 parts list

This is the "case saver" part pictured there.
Imho, it's of dubious utility and I believe it was just a stop-gap until Honda made changes to the sprocket/chain.

[Nurse Julie]

Chain protector fitted from VIN:1026144 up to 1044805.

[Mycall1983]

Agree that they have been re-stamped, probably replacement cases.  We can tell you they are not early K0(sandcasts) by the raised rectangle around the number pad.  There may be other visual cues which can narrow down roughly when these engines may have been made.  Some more good pictures may get us started.

Yeah I’d say the dealer just copied the original numbers without the CB.

[Mycall1983]

Here is a no stamp newer replacement engine case removed from a sandcast bike. It has the Sandcast's cylinder and head. It didn't get numbers but did get the three punches from the factory recall that addressed the chain breakage.

No idea the engines came as part of a mass purchase of parts.

[newday777]

... Many cases were replaced because of a busted drive chain that put a hole in the original cases.
...

Quick question!  I've owned my K1 750 since 1971 and seem to recall a Honda "recall" that installed a protective shoe or guard of some sort to protect the cases in the event of a broken chain.

But when I recently resurrected the bike after a thirty year hiatus, I was surprised NOT to see any sort of a add-on chain guard around the final drive sprocket.

I know I replaced the final drive sprocket, rear wheel sprocket and chain at some point in the distant past but don't remember dealing with any "extra device" that I might have pitched.

Can anyone post a picture of the Honda chain guard device?  Or did I dream all this up?

ZT

That was for the front sprocket area as bryanj and CycleRanger showed, not for the rear sprocket.

[Don R]

 It was a replacement empty case for a broken engine (probably by one of the legendary chain failures) bike. All of the original parts were saved and installed into it.
 I think the three-dot recall included a larger front sprocket, new chain and moving the battery drain so the acid didn't drip on the chain, on early bikes the #28 carburetor tops and 1 into 4 throttle cable got changed too. My #5511 sandcast got the three dots on the rear hub, apparently the tech didn't want to mark up the engine.
 I didn't find my chain guard yet. The 76 Hondamatic I parted out has a chain guard that goes on edge rather than flat. I would expect if to work better, it was very close to the center of the rollers and seems like it would be more likely to keep a chain from bunching up. It didn't fit in a 5-speed engine though.

[ZTatZAU]

Here is a no stamp newer replacement engine case removed from a sandcast bike. It has the Sandcast's cylinder and head. It didn't get numbers but did get the three punches from the factory recall that addressed the chain breakage.

Thanks Don!  I had never heard about the three dots before.  There are no dots punched on my K1, so I guess that means... no chain guard recall was ever accomplished.  Does that sound right?

Pic from CMSNL K2 parts list

Pic from CMSNL K2 parts list

This is the "case saver" part pictured there.
Imho, it's of dubious utility and I believe it was just a stop-gap until Honda made changes to the sprocket/chain.

Appreciate the pix guys!  The guard is just what I had pictured and expected to find under my ("final drive") sprocket cover.

Chain protector fitted from VIN:1026144 up to 1044805.

What happened with 750s after vin 1044805?  My vin is 1072186.  Did a new redesigned chain and sprocket, or other improvements, eliminate the need for the add-on guard?
ZT

[Don R]

 I think the three punch marks were a K0 thing, the chain issue and carb cables were corrected on new bikes so by the time the recall happened. I'm unsure when the case guard came and went. I don't think I have one on a bike here, but the guard I have has met a chain up close before.

[HondaMan]

... Many cases were replaced because of a busted drive chain that put a hole in the original cases.
...

Quick question!  I've owned my K1 750 since 1971 and seem to recall a Honda "recall" that installed a protective shoe or guard of some sort to protect the cases in the event of a broken chain.

But when I recently resurrected the bike after a thirty year hiatus, I was surprised NOT to see any sort of a add-on chain guard around the final drive sprocket.

I know I replaced the final drive sprocket, rear wheel sprocket and chain at some point in the distant past but don't remember dealing with any "extra device" that I might have pitched.

Can anyone post a picture of the Honda chain guard device?  Or did I dream all this up?

ZT

I've got one (maybe more?), it was removed from an early K1 engine. It limits your sprocket choice to 17T or 16T, you can't fit the later-used 18T front sprocket in it. PM me if interested.

[Don R]

 Maybe that's why I didn't leave mine in, I like the 18T front sprocket, especially on an F transmission. 

[HondaMan]

Here is a no stamp newer replacement engine case removed from a sandcast bike. It has the Sandcast's cylinder and head. It didn't get numbers but did get the three punches from the factory recall that addressed the chain breakage.

Thanks Don!  I had never heard about the three dots before.  There are no dots punched on my K1, so I guess that means... no chain guard recall was ever accomplished.  Does that sound right?

Pic from CMSNL K2 parts list

Pic from CMSNL K2 parts list

This is the "case saver" part pictured there.
Imho, it's of dubious utility and I believe it was just a stop-gap until Honda made changes to the sprocket/chain.

Appreciate the pix guys!  The guard is just what I had pictured and expected to find under my ("final drive") sprocket cover.

Chain protector fitted from VIN:1026144 up to 1044805.

What happened with 750s after vin 1044805?  My vin is 1072186.  Did a new redesigned chain and sprocket, or other improvements, eliminate the need for the add-on guard?
ZT

Boy, that's a loaded question!
Here's the largely hidden factory changes in the 750K1 comprising the 11/70 "silent update", which corresponded with the intro of the new chain:
1. 17T countersprocket, 100-link chain.
2. new Diamond XL-style chain, made by RK of Japan.
3. steel countersprocket chain guard (also available free for earlier bikes, along with RK chain if being officially 'recalled', required new chain also).
4. swingarm bushings changed from the early zamac plastic to phenolic (didn't self-crumble if ungreased) to preserve rear-wheel alignment in frame under power.
5. longer drain hose for battery's overflow port, and instructions for re-routing it (DonR noted above).
6. for earlier bikes that put racing stripes down the back left shoulder of their jacket, an extended chain guard.

Inside the engine, the clutch also 'lost' the 2 wires that held the back 2 steel plates toward the rear of the hub, to reduce their tendency to stick. It was at this time that an 'unofficial' memo was circulated about putting in some oiling holes in the inner clutch hub (sandcasts lacked these, as did many K0 and some early K1) if there weren't any. This was said to reduce the "suddenness of the clutch engagement" and to "extend the life of the clutch friction plates" in those almost-oilless wet clutches. We also enlarged the oil feed hole in the right end of the mainshaft (inside the clutch hub) to add some more oil to the clutch. (I mentioned some of this in that sandcast rebuild I did 2 years ago).

[HondaMan]

Maybe that's why I didn't leave mine in, I like the 18T front sprocket, especially on an F transmission. 

I tried to fit one over my K!/K2 engine's front sprocket, but it requires the 17T size. I use that sometimes if I know I'll be stuck riding more in city than freeway, lets the engine rev a little more freely in 30-40 MPH riding.

[bryanj]

The recall removed the 16 tooth as Honda decided it was too small and causing chain break, 17 tooth became the standard size

[Don R]

 When we have these discussions, I always learn some things that I didn't know or bother to find in the book. The case with no numbers in the pic is destined for my 11/69 K0 to replace the K3 836 in it now. The blank number motor has sandcast internals in it since it was a replacement case in a sandy.
  I'll make a note of things to check such as the clutch oil upgrades and put it with the engine. My plan is to use that motor with an ebay find, NOS 1978 Wiseco 811 kit, unless a numbered case in the 14,000 neighborhood turns up.

[ZTatZAU]

When we have these discussions, I always learn some things that I didn't know or bother to find in the book. ...

Same here, Don!  The info provided here really helped with my fading memories.  Turns out my K1 (12/70) CB750 (1072186) currently has an 18 tooth installed so would not be compatible with the case guard.  Whether or not my K1 originally came from the factory with an 18 tooth sprocket, I'm still not sure.  Maybe someone can help with that info?

I know both chain sprockets were replaced somewhere along the way.  Could it be that my recollection of the recall was to install an 18 tooth sprocket rather than installing a case guard?

ZT

[69cb750]

Turns out my K1 (12/70) CB750 (1072186) currently has an 18 tooth installed so would not be compatible with the case guard.  Whether or not my K1 originally came from the factory with an 18 tooth sprocket, I'm still not sure.  Maybe someone can help with that info?

11353-300-010 Case guard CB750E-1026144 to CB750E-1048399
11353-300-030 Case guard CB750E-1048400 to CB750E-2200000
23801-300-620 Sprocket 18 tooth 1971
All 71 bikes came with case guard and 18 tooth sprocket.

[ZTatZAU]

Turns out my K1 (12/70) CB750 (1072186) currently has an 18 tooth installed so would not be compatible with the case guard.  Whether or not my K1 originally came from the factory with an 18 tooth sprocket, I'm still not sure.  Maybe someone can help with that info?

11353-300-010 Case guard CB750E-1026144 to CB750E-1048399
11353-300-030 Case guard CB750E-1048400 to CB750E-2200000
23801-300-620 Sprocket 18 tooth 1971
All 71 bikes came with case guard and 18 tooth sprocket.

Thanks for your reply 69cb750.  Just when I thought all this was making sense, I'm confused again.

It was my newfound understanding that the case guard does not fit over the 18t sprocket.  I understood the chain guard was Honda's "temporary fix" for the early 16 & 17t sprockets and then Honda went to the larger radius 18t sprocket and a heavier chain... after which there was said to be no reason to install the case guard.

So I'm pretty sure your last statement can't be right???
ZT