Brendan’s 900SS

This Ducati used to belong to motorcycle journalist Mac McDiarmid, who was involved with the 1980s endurance race outfit Team Bike (howardleesracing.co.uk). The team’s adventures, written by Mac, Howard Lees and Julian Ryder, were a high point of Bike magazine in those days. Brendan got hold of the Ducati through Tom Stewart, another Team Bike member, and the team’s engine builder Brian Capper had rebuilt the engine before his death from cancer in 2014.

Brendan had never had it running particularly well. Mac had fitted a 5Ah battery, and it kept running flat, which resulted in no ignition. The loom was 41 years old, with various repairs, and the bike still had the original zener diode setup to regulate the charging voltage. There were burn marks round the alternator connector. Brendan wanted long term reliability, so he decided on a new loom, with an Electrexworld regulator rectifier to bring the charging system up to date. He also decided on a Shorai lithium battery, which fitted the same space as the old lead acid unit, but had three times the capacity.

Because of the way Ducati built looms in those days the new one could be much smaller and neater. The bike ran OK afterwards but was a pig to start and had a strange charging problem, going up to 18 volts. The starting trouble turned out to be corrosion inside the carbs – a frequent problem when old bikes are stored with modern fuel, which contains water-absorbing ethanol. A clean up, plus new pilot jets, o rings and a new float bowl sorted that out. The charging issue was a tiny short in the stator coil which couldn’t be detected in a static test. We got that repaired at West Country Windings. With a new rotor the bike charged perfectly at 13.8 volts – comfortably under the 14.4 volt maximum for lithium batteries.

It runs beautifully – a testament to the skill of its engine builder.