Meet Sylvie, the '68 Bonneville Bobber by Andy McNamara
The story, straight from a first time builder…
Sylvie started life as a 1968 Triumph Bonneville T120 650cc. By the time I found her, the frame and motor no longer matched – both from 1968, but not originally paired together. Common enough with these old bikes. The tank was from a TR6, the parcel grid was from a pre-unit Triumph and the front end was upgraded to a 1969 twin leading shoe drum brake. I note all this because I had plans to do some major changes, so I was on the look for a project bike that wasn’t a resto quality survivor. It would be a sin to do what I did to her if she were a barn fresh, all original matching bike. Sylvie ran, and was complete, and the price was right – so I popped on her.
I rode her for a few hundred miles before she started having some major issues. She was sluggish, even for a 50 year bike, hard starting, was having charging/battery issues, the carbs had a tendency to stick open (not fun), and finally the tank which attracted me to her spring a leak through the sheet metal (really not fun). Thus began our journey together. The plan was to create a stripped down, raw bobber. Remove whatever was non essential. Make her a rigid, big fat rear tire, upgrade, repair and replace whatever needed tending to. Seemed easy enough…
So I tore her down, removed all the original pieces I didn’t need and sold them to fund the rest of the build. You’d be amazed how much you can get for an unmolested 1968 Triumph Bonneville chain guard.
THE BUILD PROCESS
Starting from the rear, I had the original rear wheel hub and brake re-laced to a Harley rim and mounted Firestone Champion Deluxe tires. All new bearings and made some new spacers. Getting the fat rear to fit in the frame while not rubbing the chain was a bit of a trick, but I finally got the offset right. I installed the bolt on rigid rear frame section – made it straight and true and locked it down.
I modified the rear section for the battery and fabricated the supports. Room was tight, so I went with an anti gravity battery – pricey but tiny, light and better performance than the lead acid batteries. I fabricated the mounting points and hung the oil bag. I added a duck bill rear fender, trimmed to fit, and mounted it to the frame using threaded bungs. I went with a strutless rear fender, again to avoid any unnecessary clutter.
*B3 Editor’s Note: Pro tip, watch the evolution of the shop shed and the tools, as well as the bike.
Moving to electrical – someone had upgraded to an electric ignition but come to find out one of the ignition coils (which were stamped MADE IN WEST GERMANY to give you a sense of the vintage) was dying if not completely dead. This explained the sluggishness and hard starting. Moving on to the alternator, well the pictures tell the story. The stator was roached and the rotor also well past its prime – it had barely any magnetism left. This explains the charging and power issues. I ended up replacing the entire ignition system with all new high output components. I added a micro switch on the new handlebars to keep the visible wires to a minimum and added a kill switch.
As to the motor, compression was good, and the motor ran, so I resisted the urge to crack the cases. I reset the valve lash – which was way off when I checked it. I had tried to refurbish the carbs, but they were too far gone. With years of use and over-tightening, they had become oblate and wouldn’t seal right and would stick open. So those had to be replaced out right. Got a new production slim-line petrol tank which better fit the bike. I also added a cool little design element, I inset a 2 pound coin in the gas cap.
I refurbished the oil pump, and added a slick oil cooler inconspicuously hidden behind the license plate with all new oil lines. I modified and fit the license plate frame and used a stop light that is a remake of an old Ford brake light, fitting the aesthetic I was going for.
*B3 Editor’s Note: Fun fact, with this little guy, the oil is cool enough to touch after going for a 30m ride. (We don’t recommend testing with bare body parts, though.)
I spent what seemed like forever sanding and polishing the engine covers which were heavily pitted and scratched from years of honest use. As to the exhaust pipes, I went with drag style pips with no silencers run down the sides to compliment the stance of the bike. I fabricated some custom brackets that are hidden from sight.
*B3 Editor’s Note: while the shed is cool, it’s freezing too. Sylvie spent most of her winter inside the house on the first floor. Most of the work was electrical, but nothing was restricted.