I decided to begin with the ignition circuit, because if the engine wouldn't start there wasn't much point rewiring the whole bike. I bought some new points, coil and used a big capacitor in place of the battery. The engine made some encouraging noises until the fuel started leaking out of the Wop carb. A days testing of my patience finally rebuilt that horrible component (Amal carbs are much better). The next kick nearly broke my ankle as the bike kicked back - these left hand kickstarts don't help. After recovering my nerve I tried again - a flame shot out of the carb. I decided to check the valve timing. It was OK, but the exhaust valve had too much clearance.
I also reset the points. This time the bike coughed. Eight kicks later, just before I finally expired, it fired up. The noise from the open exhaust was incredible. World War Three had begun. I couldn't hear any engine faults, so I felt happy enough to renovate the cycle parts. I got lucky here. Picking up a box of cycle parts for £50.
They needed work (don't they all) but it contained the neat twin filler petrol tank, half fairing and seat/tail unit. It took a weekend of scraping, filling and much elbow grease to get them ready for painting. The frame was sand blasted by a friend in the trade. A couple of cans of paint and an electric spray gun later I had an assembly of black and blue components. The finished product looks much neater than the stock bike, which in the late sixties lacked the later classic styling of the more popular Duke singles.
Starting was still hazardous, but got better when I fitted a battery. The engine is good for about 85mph, but. more importantly has enough power to cruise at 70mph and does 95mpg. Vibration is bad at low revs and above 80mph, but It smoothes out at speeds between 40 and 80mph in top gear. The engine drinks oil at a pint every 150 miles, so it may soon need either a re-bore or valve regrind, but I have most of the bits, so no great problem.
The suspension might once have been hard, but they're over 15 years old now and the springs have sagged a little. There's hardly any damping, so bumpy curves can knock the bike way off line, but as it only weighs 300lbs it's easy enough to control. Straight line stability is fine and it feels very secure in the wet.
Compared to the CD175s, B120s and GT250s I've owned in the past it's way ahead. Although the suspension sags, it still doesn't absorb the bumps and the skinny seat means long distances are most uncomfortable (not helped by the clip-ons and footrests too far forward).
Engine vibration loosens exhaust pipes, footrests and side panels; it also blows head-lamp and tail bulbs every 1000 miles. Both brakes are SLS, but work OK up to 70mph. Fade from the front can occur from repeated high speed stops. The clutch needs much muscle and drags if used in town.
The contact breakers need adjusting every 500 miles, the valves every 1500 miles and the carb goes out of adjustment after 600 miles. But it's all easy to set up. The bevel drive valve gear is a bit. of nuisance to build, but the motor is generally easy to strip down. It's cheap to run, fun to ride and despite being non-original should keep up in value, ensuring that won't cost me in depreciation.
Ian Cooper