Differences - visually between CB72 and CB77 crankshafts

[e3steve]

I my head (....I hear voices......!) the only logical difference I can imagine is that the 72 crank ass'y is lighter, hence the different part nrs; far fewer 72s were ultimately produced, therefore the price was higher due to lower volume. Maybe that would make some sense?

How many CBXs are you hoarding these days, btw?

G'luck with the latest CB72 project! How about some pics? They'll need compressing down to <512KB.

[Dennis Lodge]

Hi Steve,

Yes I did think it was governed by volume sales/production and the need for spares.
Best to email me re pictures. Meanwhile I will take some!
Although still involved with CBXs I no longer own any. Had a clear out some time back.
cheers
Dennis

I my head (....I hear voices......!) the only logical difference I can imagine is that the 72 crank ass'y is lighter, hence the different part nrs; far fewer 72s were ultimately produced, therefore the price was higher due to lower volume. Maybe that would make some sense?

How many CBXs are you hoarding these days, btw?

G'luck with the latest CB72 project! How about some pics? They'll need compressing down to <512KB.

[jensen]

Hi Dennis,

First of all I have to say that I never saw a crank with two oil holes, but maybe I wasn't paying enough attention, can you post pictures ? I have several CB77 and CB72 cranks, I will measure the features of these cranks and compare the total weight of the cranks.

I know that the CB72 cranks are balanced different then the CB77, and that the price of a CB72 crank is indeed higher because it is produced in lower numbers. The CB77 was designed mainly for the US market, a much bigger market then the European market. The CB77 in Europe is a rare bike, in the US it's the other way around. An American supplier doesn't have much CB72 cranks, thus the price is higher, at least that seems logical to me. A small difference in machining will not result in a 1000 USD price difference.

There are at least three different cranks for the CB72, the difference is the type of bearing, and the spine diameter (actually there are two different cranks (splines), and a small change in bearing, resulting in another p/n.

p/n 13000-268-010 runs from 010001 to 112068, bearing 91102-259-010 runs also to the same engine number, so the crank with the bearing got another p/n.

p/n 13000-268-020 runs from 112069, with bearing 13411-268-010

p/n 13000-268-030 runs from engine number 1008173 to the end of production. The differences between this crank with the 020 is the bearing again and the diameter of the spline area, now the bearing 13411-268-020 is attached, thus resulting in another crank p/n, and it needs the other chain sprocket, 13611-259-020 instead of the previous used 13611-259-010.

Then there are small differences, not resulting in p/n changes, because these were fitting in the cases without chancing other parts.

Jensen

[Dennis Lodge]

Hi Jensen,

Further checking shows that one hole is within the hollow crank end which is blind the other hole being in the oil fed part.

Pictures attached.

cheers

Dennis

Hi Dennis,

First of all I have to say that I never saw a crank with two oil holes, but maybe I wasn't paying enough attention, can you post pictures ? I have several CB77 and CB72 cranks, I will measure the features of these cranks and compare the total weight of the cranks.

I know that the CB72 cranks are balanced different then the CB77, and that the price of a CB72 crank is indeed higher because it is produced in lower numbers. The CB77 was designed mainly for the US market, a much bigger market then the European market. The CB77 in Europe is a rare bike, in the US it's the other way around. An American supplier doesn't have much CB72 cranks, thus the price is higher, at least that seems logical to me. A small difference in machining will not result in a 1000 USD price difference.

There are at least three different cranks for the CB72, the difference is the type of bearing, and the spine diameter (actually there are two different cranks (splines), and a small change in bearing, resulting in another p/n.

p/n 13000-268-010 runs from 010001 to 112068, bearing 91102-259-010 runs also to the same engine number, so the crank with the bearing got another p/n.

p/n 13000-268-020 runs from 112069, with bearing 13411-268-010

p/n 13000-268-030 runs from engine number 1008173 to the end of production. The differences between this crank with the 020 is the bearing again and the diameter of the spline area, now the bearing 13411-268-020 is attached, thus resulting in another crank p/n, and it needs the other chain sprocket, 13611-259-020 instead of the previous used 13611-259-010.

Then there are small differences, not resulting in p/n changes, because these were fitting in the cases without chancing other parts.

Jensen

[jensen]

Hi Dennis,

In short, I never saw this before, and I checked my own cranks without any positive result.
Can you measure the crack bearing diameters (all four of them) and take a picture of the other side of the crank ?

I divided the following info in facts and possibility's (assumptions). Facts are real, and can be proved, possibility's however, should be proved, and as long there's no proof (both sides) it's called a theory.

Facts :

It seems to be an early CB72/ /77 crank (bearing rotor side), so p/n 13000-268 (275)-010. You also mentioned that there's no actual open connection between the two holes within the shaft, and that is weird indeed and doesn't make sense engineering wise.

Assumptions (but I rather call it possibility's or theory)

I am aware of the fact that the first crank that Honda shows in the part manuals is a 010 (for the CB72 as well as for the CB77), normally it starts with 000, so there could be another one, a predecessor, but not in the books, for unknown reasons. As I fully understand that the last three digits of a part number doesn't give any info on the part itself other then manufacturer or pointing out special parts or special treatment (racing, police, or destination / country), I still find it strange that it starts with 010.

I have an indirect proof of a possible existence of a different (000 ?) crank, and that is a (lower) crankcase of an early (no primary chain tensioner and sand casted surface) CB72 with a larger crank bearing diameter. I have never seen a complete crank with that larger diameter bearing.

It is a possibility that this crank has also the holes you show, but that is to be proven by the diameters of the bearings (still it is no proof for the existence of a 000 crank, but it is a proof of the fact that there are more crank types then the three Honda mentioned in the parts manuals,

It certainly has my attention,

Jensen

[Dennis Lodge]

Hi Jensen,

Find below pictures as requested with diamensions included. Also I managed to find my Nos 1961 crankshaft which is missing its outer bearings, all diamensions included. Certainly the balance holes in the CB72 I now see are smaller that the other crank.

regards

Dennis

[Dennis Lodge]

Hi Jensen,

Two more images that would not attach.

regards

Dennis