Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board T120 Gearbox Camplates, Plungers & Springs

While re-building my '68 T120 I stumbled into the dark hole of gearbox selector camplate, plunger, spring and holder changes made during the 1968, 69, and 70 model years. I learn a lot from the forums, so I'm always inclined to pay it back and even forward. I know many will think me crazy for diving this deep, but I do think this is useful information for those who want to try to achieve the best shifting possible from the 4-speed gearbox. My report is a pdf which can be downloaded from Google Drive here: https://drive.google.com/file/d/19TLSiaeshLao7b2yNrk9uFTD8l1qUe7w/view?usp=sharing

jeez, that's fantastic


now do the five speeds.

I wonder if there is something like that for the 500 unit.......

Cheers, Wilf

Wow Mike, very impressive work and very much appreciated.
Cheers,
Bill

Now go into the different gear and shaft types over those years..................

There is a good wall chart for that (from the factory). Sadly, it does not come with the magnifying glasses needed to read it! I believe both Coventry Spares and JRC offer it to their dealers. I got mine from Dan at Franz & Grubb.

Great, thanks!

A big round of applause for Mike for illuminating several facets of Triumph gearboxes which have long been sources of rolling confusion! Great work, MIke, Congratulations on such a useful outcome of your hard work and dedication!

Great summary, Mike
Well done and thank you.
Everyone with a Triumph four speed box should have a copy of your summary---saved in their computer or printed off and filed.

Great work Mike!
I saved it and I don't even own a four-speed.

Somewhere there must be a guide to upgrades to early five speeds which don't involve replacing the whole thing?

What do you suppose the notches on the cam plate between the gears were for? It would seem to me that it would make it more likely to find a false neutral.

Those are just to drive you crazy trying to index the quadrant. Just like the crossover shaft on the T160.

Great question! I wish I knew. I didn't come across any info in my research to answer that. I bet John Healy knows.

I encountered a unique shifting problem after updating to the 1970 Gear Selector Camplate and appropriate plunger, spring, and holder. Without going into the details, what I found (thanks to a conversation with Don Hutchinson and one with Mitch Klempf) was that the Index Plunger Holder (57-2172) needed to have the top machined down to allow the Camplate (57-4055) proper clearance. I have updated my write-up: Triumph 4-Speed Gearbox Changes 1968-70 and the revision can be downloaded from Google Drive: https://drive.google.com/open?id=19TLSiaeshLao7b2yNrk9uFTD8l1qUe7w&authuser=mike%40james5.com&usp=drive_fs[i][/i]

Mike , Your information was very helpful to me. I found it on Hermit's Bonnie Reference. I am just about ready to button up the tranny - waiting for a clutch rod buushing. Previous owner drove out the bushing for some reason.
Thanks very much.
Al