Hi Guys I have been rebuilding the gearbox on my 69 Bonnie when I inspected the shifter cam plate I found it worn and decided to change it , I managed to find one on e-bay but when it arrived it was bigger and had less detents in it , I looked in my manual and it seems to picture my origional cam plate and uses one of the detents to hold the plate in place when putting the gearbox bad together , my question is will the new bigger plate work and why is it different ? Thanks Max
Do you have a 4 speed? I think they are all the same. Well, at least the ones I've seen. I've interchanged bronze with steel forks without having any problems with the cam. What was worn on the cam? Mike
Yes it is a 4 speed and my shifter fork are steel with rollers , the shifter fork groove is worn as well as the outside edge where the sprung plunger rides , it would probably be Ok but I figured that as I had it in my hand now would be the time to change it instead of second guessing myself the middle of next summer Max
The groove from the indexing plunger probably makes it shift smoother than originally. I do not know why in Tartarus they did not put a roller on the end. It could be oriented by extending the cylinder over the sides of the camplate. The fork groove is a problem. It might let the gears disengage. Triumphs do not have undercut dogs to help keep them from pushing apart under load.
Additionally, the lack of the extra neutral position between 2nd and 3rd will not keep you from setting the camplate in that position for assembly. Obviously the camplate can still be set in that position, the notch simply makes it stupid-proof.
The truth is that the gear teeth on the quadrant that interface with the gear on the rear of the camplate are so course that the camplate being off 1 degree really doesn't slow you down on assembly. The large teeth allow for a great deal of inaccuracy during the quadrant timing process, and the job goes just as fast.
So there is nothing to loose in the newer design camplate and certainly smoother shifting to gain.
Joined: Oct 2001 Posts: 24DC
BritBike Forum member
BritBike Forum member
Joined: Oct 2001
Originally Posted By: John Healy
The 57-4055 is a forging and in IMHO a quality piece. It should be used with the 57-3660 detent as suggested by Mr-runner above. It is my favorite 4 speed camplate!
I need to replace the original camplate in my '68 T120.Although I can get the correct camplate for that year, I would prefer to take the opportunity to improve the shifting. From reading the above, it would appear that the 57-5055 cam and 57-3660 plunger are compatible with all of the older components? Is that correct? (I'd rather not have to replace the selector forks and plunger housing if not necessary) Thanks
Without taking the time to look up the parts you mentioned, IME almost all the 4-speed parts since the mid-1950's are interchangeable... provided they are of the same ratio set and tooth counts.
There are minor annoying differences like the layshaft resident speedo drive, and the longer journals of the pre-unit layshafts. But generally speaking shifter camplates and plungers would be a direct swap.