1962 Was the final year of the Pre Unit 650's, many significant changes were made for the '63 Season all of which paved the way for the next 2 decades of production. My passion is with Pre Unit construction machines and the '62 Bonnie was a fine example of the iconic T120. Here is a blog centered around a bike I restored in 2014 that now sits in the prestige collection of an important client of mine.
Pictured below is the bike how I purchased it back in 2013, still with many original parts and in running condition (despite a broken Crankshaft, see below). Click on the images for supersized versions.
Fitted with an Alfin custom Alloy Cylinder otherwise all as standard with the original Amal 376 Monobloc Carbs,
After chemical stripping the sheet metal was in excellent condition. The front blade was supplied by Pre Unit specialists Ace Classics as the one that came fitted was a custom aftermarket type
The Drive end of the Crankshaft was broke in two and was clamped together with a stud, amazingly it did hold together until teardown for restoration.
Replacement Crank was reground and then dynamically balanced
My least favorite job on a Triumph is removing and replacing the Swing Arm Spindle. After years of neglect rarely ever seeing a squirt of grease these are more often than not a real pain to remove. Anyway, new bushing were fitted as was a new Spindle.
The Alfin Cylinder was replaced by a stcok one and bored .040. Boring and Cylinder Head work was performed by Dan over at Franz and Grubb in North Hollywood.
A new High Gear bush is almost always required during any Gearbox overall.
New Shock Absorber Rubbers fitted to the Clutch Center.
A few shots during the rebuild.
Original Dunlop Rims were re-plated. The Dunlop stampings survived the process nicely.
Pre Units from 1960 to 1962 came in a Duplex Frame
376 Amals were refurbished.
Petrol Taps introduced for the 1962 models were stripped for Nickel and Chrome.