cam sprocket question

[conbs]

Per Bill Silver:

"The camshaft timing is all the same, but there were revisions to the camshaft
splines and to the design of the camshaft sprocket assembly. The original 14320-259-020
was superseded to -030 and finally to -040, when the first versions, which were quite
robust were replaced with a more streamlined and lighter part. The first change (-030)
was from the heavy type to the lighter design, which had RH threads for the camshaft nut.
The second change (-040) was to LH threads for the matching parts. The –040 part was
instituted at CA72E-210631 and CA77E-213875.

"The change to the smaller point cam shoulder came at CA72E-401526, CA77E-
403385, which coincides with the change in the left side camshaft half.

"Point shaft changed diameters changed at CA72E-210101, CA77E-210101."

There is no normal or abnormal for the threads/nut for the advancer unit. Just different parts depending on when your bike was made.

I think you just have to make sure your nut fits the threads on your advancer and that you have the right size points shaft to fit correctly in the rectangular hole in the center of it. whether it would be optimal or not, I have no idea, but it would seem that it should at least run and probably run pretty well.

[jensen]

Hi,

@G-man :

Some modern bikes have balancer weights on their camshafts (English bikes as well), like some triumph's.

@ Teazer : Yes, indeed very clever.

@conbs :

I know the Bill silver info, I have a copy and I read it many times, but Bill silver isn't always right, and his books don't give an answer to the questions I have. Bill probably extracted his text out of the bulletins from Honda about the changes. And he doesn't say "you can use a dream sprocket in a CB or the other way around", neither his books show a measured ignition curve of both sprockets nor he gives an explanation of having the need for two different ignition functions for the sprockets.

Did you interchange them ? and what is your experience with it ? Can you use the springs from a dream cam sprocket in a CB sprocket ? And if these are not interchangeable, how many people bought 259 springs and placed them in a CB sprocket (and the other way around) ? What happens when you do so ? Does he explain the differences between the springs ?, the ignition characteristics ?

In the past there were some questions on the forum about springs that were longer and didn't do the job, was this the above issue ?

Why are both sprockets different ? what is the need for it ? is there a purpose to have two different characteristics ?, and if yes, why ?

Is the RH thread only used in dreams ? Are there CB's out there with these weights connected to the cam sprocket ? Do all heavy sprockets have RH threads ? Does the ignition characteristic of each Sprocket (dream / CB) fit their purpose, does it mean that a dream sprocket is optimal for a 360 crank, and a CB sprocket is optimal for a 180 crank ? What kind of sprocket would there be in a CM engine (360 degree crank, but a CB cylinder head) ? What kind of thread is used on the sprocket in a CM engine ? Does a CM have the heavy cam sprocket ? And if yes, does it have the long or short advancer weights ?

This is just a summery of the thoughts I have comparing these sprockets, I cannot help it, I like to understand, not only know the differences !

I think a discussion of the above questions is far more interesting then issue's mentioned in 90 % of the threads, becuase I like to go further then the existing knowledge described on the forum, further then the knowledge described by Bill's books. The forum should be a knowledge database with ever expanding borders of knowledge driven by curiosity.

Anyone with answers ? Or am I lost ? Am I the only one who thinks this way ?

Jensen

[LOUD MOUSE]

All to many questions for a simple/short answer.
BUT HERE GOES FOR PART.
Use the parts books for the DREAM TYPE and the CB/CL72/77 TYPE engines and ya can see the answers to the SPRING and 360 VS. 180 Crank
My info shows all the DREAM TYPE used the same springs (259) as did the CB/CL72/77 (268) even the CYP77 (360 CRANK) engine used the same as other CB77 engines (180 CRANK).
The first Sprocket Assy. (HEAVY) Had Regular Direction Threads as did a Short Run of the replacement (lighter Issue to mid 1962) then came the Reverse Thread.
Have to go to a Fire Call. .................lm

Hi,

@G-man :

Some modern bikes have balancer weights on their camshafts (English bikes as well), like some triumph's.

@ Teazer : Yes, indeed very clever.

@conbs :

I know the Bill silver info, I have a copy and I read it many times, but Bill silver isn't always right, and his books don't give an answer to the questions I have. Bill probably extracted his text out of the bulletins from Honda about the changes. And he doesn't say "you can use a dream sprocket in a CB or the other way around", neither his books show a measured ignition curve of both sprockets nor he gives an explanation of having the need for two different ignition functions for the sprockets.

Did you interchange them ? and what is your experience with it ? Can you use the springs from a dream cam sprocket in a CB sprocket ? And if these are not interchangeable, how many people bought 259 springs and placed them in a CB sprocket (and the other way around) ? What happens when you do so ? Does he explain the differences between the springs ?, the ignition characteristics ?

In the past there were some questions on the forum about springs that were longer and didn't do the job, was this the above issue ?

Why are both sprockets different ? what is the need for it ? is there a purpose to have two different characteristics ?, and if yes, why ?

Is the RH thread only used in dreams ? Are there CB's out there with these weights connected to the cam sprocket ? Do all heavy sprockets have RH threads ? Does the ignition characteristic of each Sprocket (dream / CB) fit their purpose, does it mean that a dream sprocket is optimal for a 360 crank, and a CB sprocket is optimal for a 180 crank ? What kind of sprocket would there be in a CM engine (360 degree crank, but a CB cylinder head) ? What kind of thread is used on the sprocket in a CM engine ? Does a CM have the heavy cam sprocket ? And if yes, does it have the long or short advancer weights ?

This is just a summery of the thoughts I have comparing these sprockets, I cannot help it, I like to understand, not only know the differences !

I think a discussion of the above questions is far more interesting then issue's mentioned in 90 % of the threads, becuase I like to go further then the existing knowledge described on the forum, further then the knowledge described by Bill's books. The forum should be a knowledge database with ever expanding borders of knowledge driven by curiosity.

Anyone with answers ? Or am I lost ? Am I the only one who thinks this way ?

Jensen

[jensen]

Hi,

Thanks LM.

CB72 : 14321-268-020, all models, including CP and CYP
C72 : 14329-259-310, all models

If the springs are the same for a 360 crank and a 180 crank, why are there two different cam sprockets ?

So I understand that there are "light" sprockets with RH thread, used for dreams only ?, not for CB's ? No heavy sprockets with LH thread out there ? I still don't understand why having two differences in cam sprockets when the difference is NOT the 180 vs 360 crank, and not the weights on the cam sprocket.

Indeed G-man, it's time to investigate the rpm / advancing curve to see the differences.
I have both sprockets NOS, and at least 3 of them each, so that won't be to difficult.

Jensen

[G-Man]

Jensen

Just looked at the two types of sprocket again (big and small). There is nothing in that sprocket that is eccentric, therefore it cannot develop any out of balance forces to cancel vibration from any other part of the engine. The fact that it is not round does not make it eccentric.

I would imagine that Honda made it large in their first design to smooth out rotational speed fluctuations of the camshaft. A sort of flywheel. With such a long cam chain, the variable torque caused by the cam would produce disturbing changes in cam chain tension. The big sprocket would help this. Such torsional speed changes would have also affected the governor mechanism and Honda would have been careful to make the mechanism responsive to speed but immune to rapid speed changes.

As with all Honda designs of the period (check out a set of CB77 fork tubes compared with later CB400F) they paid little attention to production engineering. A camshaft in three parts with expensive splines and an ignition advancer built in, supported in four bearings and driving through a quill shaft was unnecessarily complex. Clever it may have been but they came up with simpler and more cost-effective designs soon after; which is even more clever in my book....

G

[jensen]

Hi,

Thanks G, indeed, that makes no sense, so more flywheel it is, but isn't the crank and clutch already heavy enough to play that particular role in the design ? Well, it's the only explanation at the moment which make sense, but in my experience the dream engine isn't smoother then a CB72 engine, more the other way around (probably due to the English twin configuration, 360 degree that is).

Still a lot of questions, particular the reason why.

Jensen

[conbs]

Hi,

Can anybody explain me what the differences are between a C72 / 77 and a CB72 / 77 cam sprocket other then the length of the advancer weight arms and advancer springs ? (and another function of rpm versus advance timing).

Did anyone used a C72 / 77 cam sprocket in a CB72 / 77 (or the other way around) ? and what are the experiences ?

Jensen

Per Bill Sliver regarding CB cam sprocket:

"The cam sprocket was changed along with the special nut as CB72E-213801 CB77E-212261 (right hand threads), then again at CB77E-1052547 (change in spline diameter, reduced from 17.5mm to 17mm). Left Camshafts were changed CB77E-1052547 (splines). Right camshafts were changed twice, once at CB72E-402706, CB77E1000794 (different point shaft) and again at CB77E1052547 (splines). The "000" and "010" point shafts are not interchangeable, due to diffeence in shaft diameters."

Jensen, I agree Bill Silver's info is not perfect, but I think all would agree that he is pretty darn reliable and in no event should he be ignored. In this case, the reference to the changes in part design are useful, because it at least tells you which details you will want to consider when trying to make a camshaft/advancer sprocket/points cam from a pile of CA/CB parts. I include his quotes in this thread because your question is very technical and a very large percentage of readers will not have his info.

I have not tried to assemble a CB camshaft with a Dream sprocket, but I am interested in whether it can be done and if there is a benefit. I bought CL cams and carb to put in my Dream (with porting) at some point to gain torque as you have suggested in other threads. If using a CA sprocket will give better advance, I will probably want to use one as well instead of just using the CL sprocket. But this seems like a project that could only be practical for someone with a large pile of parts for CA and CB/CL models. With all of the variables listed among the sprockets, camshafts and points shafts it doesn't seem easy. Still, I hope you or someone else will try it and let the rest of us know how it works out.