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Index to Hermit's 650 Triumph Gearbox Articles

Here is a listing of articles on assembling, indexing, and maintaining the Triumph unit 650 4-speed gearbox.

These how-to articles pertain to a 1969 Triumph T120R 650, as well as other late-60s 4-speed gearboxes using a plunger and spring. If you're researching a Triumph 5-speed gearbox, or a gearbox using a leaf-spring instead of the plunger, be aware that there are important differences. See Britbike.com links at the bottom of this page.

Links to the Articles

Triumph gearbox parts
Triumph Unit 650 4-Speed Gearbox Assembly Made Easy
A step-by-step, photo-illustrated tutorial on the clever way Hughie Hancox stuffs a Triumph unit 650 gearbox. It just doesn't get any easier than this! I'm laughing the whole time I'm doing it this way - how can it be so easy!
Triumph gearbox quadrant in 1st gear
How to Index the Triumph Unit 650 4-Speed Gearbox
Indexing the Triumph gearbox when replacing the inner gearbox cover is notoriously tricky, but it doesn't have to be. This tutorial makes it a snap! Whether you want to index in first gear, fourth gear, or neutral between 2nd & 3rd, the photos and text will show you exactly how to get it right. Maybe even the first time!
Triumph gear cluster, front view
Gearbox Photos & Photo Animation
Front View
See the exact positions of the camplate and the gear cluster in all gears and neutral, either as stills with descriptions and part numbers or as a photo animation. A diagram shows power transfer between mainshaft and layshaft gears and shows which gears spin and which gears are splined to their shafts. Even I can understand how it works when I look at the diagrams!
Triumph gear cluser from back
Gearbox Photos & Photo Animation
Rear View
The same great photos, animation and info but viewed from the back.
A Triumph plunger spring
The Spring Report - Mike James
Mike James took a deep dive into Triumph unit 650 gearbox plunger springs and came up with this detailed and superbly illustrated investigation of springs, plungers, plunger holders, and gearshift camplates, with special attention paid to the raft of changes made 1968-1970. Learn the difference between spring rate and spring force and why it matters. A must-read for those interested in a deeper understanding of these parts and how well they play together in various combinations. (PDF, 8.5mb)
Triumph gears
Triumph 650 Gearbox Reference Photos
Photo illustrations of all the Triumph gearbox parts, including the shafts, the gears, the gear shifting forks, the camplate, and plunger. Includes comparative photos of old and new parts.
Triumph gear box
Triumph Gearbox Assembly Methods Comparison
There are many ways to put a Triumph 650 gearbox back together. Here's a side-by-side comparison of three methods: the Triumph workshop manual, Haynes, and the master himself, Hughie Hancox.
The Hermit
The Bonnie Ref: A Hyperlink Junkie's Field Guide to the Bonnie: Gearbox This is the gearbox section of "The Bonnie Ref", a compendium of information about caring and repairing the 650 Triumph Bonneville. Includes ramblings of Bonnie's non-mechanically inclined owner. It's a warehouse of highly organized easily-accessed info, including essential factory gearbox bulletins, photos, full parts, and links to informative on-line discussions.
Engine base for a Triumph 650 Engine
Thrust Washer Locating Peg Repair
Using a custom jig to replace the locating peg for the DS layshaft needle bearing thrust washer after it became damaged.
Engine base for a Triumph 650 Engine
Engine Base
A plywood base to facilitate pressing of the drive side (DS) needle bearing in a Triumph 650 4-speed gearbox.
Photo of Triumph Gearbox Mainshafts
Clearances and Specs
Clearances & Specs for Selected Gearbox Components
The Hermit
Gear Oil & Yellow Metals Experiment Opinions differ about the safety of using GL5 gear oils in old motorcycle gearboxes with their bronze bushes and thrust washers. See the results of Hermit's 2-year gear oil experiment. Who you gonna believe? Me or your own lyin' eyes? Keep an open mind, now.

Links: Indexing Triumph 5-Speed & Leaf-Spring Gearboxes

Here are some threads on Britbike.com that feature posts by John Healy, the Triumph Board moderator. In his posts Mr. Healy references the differences between 4- and 5-speed gearboxes as well as gearboxes using spring and plunger versus those using the leaf-spring. Pay attention!

Link: Upgrading the Triumph 5-speed gearbox

With its great photos and copious informed discussion, Kevin Roberts' BritBike.com post on upgrading his 5-speed gearbox is a great resource for anyone delving into a Triumph 5-speed.