X crossing 2nd gear set and 3rd gear set.

[johnniespeed]

I have researched this about as far as I can find, I know for sure it can be done.
I know for sure this is suggested as an improvement for the CB77 SuperHawk.
I do not know if this is also suggested for the CA77 Dream.
Anyone with knowledge, opinions or advice is welcome to share their info.
Also the part numbers for the recall 2nd gear cotters I would like to have.

[sky.fred]

I can't give a definitive answer to this modification question, but having replaced the rotary gearbox mechanism on my C72 with a CB77 mechanism, I can confirm that the gearboxes are identical and interchangeable between CA and CB.
viewtopic.php?f=22&t=7643370&start=56
To make this modification, I had to study at length the different types of gearbox mechanisms and I didn't see any specificity in the OEM part numbers for these parts depending on the year and model (C72,77 or 78), the only difference I've found is between the "rotary" and "classic" boxes but Honda parts lists are sometimes wrong.
And a gearbox with forks and drums in good condition is very smooth and precise. A problem between the second and third may be due to wear.

[johnniespeed]

Sky Fred, thanks for your reply and great information.
I know that complete Super Hawk transmissions can be interchanged into the Dream or vice versa. ( CB to CA and even CA to CB)
I know that the Super Hawk shift dogs are undercut and Dream are square cut.
I know that the Super Hawk gear ratios are slightly different than the Dream.
I know that x-crossing the Super Hawk 2nd set and 3rd set makes the shift spacing ( RPM drop) linear or more even and seems to be suggested by most everyone.
What I don't know, is whether X crossing of the 2nd gear pair and the 3rd gear pair for the Dream is a suggested improvement.
This forum has members with a wealth of information and I am hoping to learn.

[sky.fred]

I can't help much because I'm worried about the translation of "X crossing" (I'm French) and I can't figure out what it is or what the improvement you mention might mean.

[johnniespeed]

On the CB77 Super Hawk, if you remove the second gear from the mainshaft and remove the other second gear from the counter shaft, then remove the mainshaft third gear and the countershaft third gear. Then swap them around in an X pattern. When done the two second gears are where the two third gears used to be, and the two third gears are where the two second gears used to be.
This is a very common modification that makes the shifting RPM drop linear for SuperHawk. I have found several references to this mod on the internet, It has been talked about much with the SuperHawk owners.
The two transmissions can be interchanged completely but they do have different gear ratios. Besides the differences in gear ratio, the Super Hawk CB77 has undercut shift dogs and the Dream CA77 has straight cut shift dogs.
I am trying to find out if this improvement is also suggested for the Dream CA77, I have heard rumors about doing this on a Dream, I am just trying to confirm.

[Tim Allman]

Bill Silver in his Restoration Reference Guide discusses this a bit. The main benefit is the decrease in the gap between 1st and 2nd gear. The cost is in the shortening of 3rd gear so you lose some ability to pass quickly, pull up long hills and deal with strong headwinds. He points out that the CB/CL72s benefit greatly as they don't have the torque to handle the 1st to 2nd drop in engine speed as they fall off the power band.

So, if you like high speed and the ability to get up there by stretching 3rd and dropping into 4th "X-ing" may not be for you but those who ride mostly in the city may like the new ratios. Here they are from Silver's manual.

Code: Select all

	Stock	Modified
1st	17.52	17.52
2nd	10.46	11.70
3rd	 7.32	 8.26
4th	 6.26	 6.26

[johnniespeed]

Tim, thank you so much for your great reply, there is no question that the X mod is great for the CB77 SuperHawk.
But what about the CA77 Dream that has different gear ratios ?
Does the X modification benefits still apply to the Dream CA77 ?