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World record attempt: Taking a Bonneville to Bonneville

By Mario

Read about Fergus Maynes, who hopes to break the world speed record for a production class pushrod-engined 650cc using his 1970 Triumph Bonneville.

Fergus Maynes is no stranger to the salt, having raced a ZX-10R at Speed Week in 2016. But the discovery of a long-established record for 650cc pushrod production bikes is what really turned his head. For 2018, he’s putting together an assault, starting with the purchase of a 1970 Triumph Bonneville.

Following in the footsteps of Burt Munro can at once seem impossibly romantic and downright foolhardy. It’s a long way from New Zealand to the salt flats of Utah, and the competition for speed records is intense. But for long-time circuit racer and well-known motorcycle industry figure Fergus Maynes, it’s a journey that’s definitely worth pursuing. 

‘Ferg’ first attended Bonneville’s Speed Week, traditionally held in August, back in 2016. It had been a long time between drinks for aspiring record breakers, with racing cancelled due to atrocious track conditions in 2014 and 2015. For the 2016 return, the track was not in prime condition and the runs shorter than usual, with Ferg’s passes on a ZX-10R failing to trouble the record books. Even so, he was hooked and determined to do it again—and on something with a chance of taking a record. 

Trawling through the record tables, Ferg spotted something deeply interesting. The world speed record for a production class pushrod-engined 650cc ‘bike was a seemingly attainable 106.4mph, and held by a Triumph Bonneville T120R. As any fool knows, the ‘120’ referred to its top speed, right? At least that was its reputation among leather-jacketed rockers hanging out at the Ace Café. But the salt is a different thing. Traction is poor, resulting in constant wheel slippage, and there’s more rolling resistance to overcome than on tarmac. Then there’s the elevation: a power-sapping 4,219 feet. Even so….

Standard, not standard

The production class rules of the Southern California Timing Association (SCTA) are a curious hybrid. On the outside, the 'bike must adhere precisely to the way it left the factory. Not so much as a footrest rubber can be different. On the inside, however, it’s pretty much open slather.

Job #1 for Ferg was to find a bike. As far as fast 650cc pushrod motors go, Triumph’s T120R is pretty much self-selecting. Modern bikes are OHC and the Bonnie’s contemporaries were heavier and no more powerful. Of course it had to be absolutely 100% original, and what looked like a good one came up in California. After shipping to NZ and taking it out of the container, Ferg could scarcely believe his luck. Not a thing had been changed since it came off the production line at Meriden in 1970, right down to the awful tyres. And it ran great: starting first kick after some traditional tickling of the Amals.

Fergus Mayne standing with his Triumph Bonneville T120R

With a relatively limited budget, Ferg is going to prioritise getting the most out of the motor for the least amount of money, but it is going to be extensively rebuilt. He’s already got a spare pair of downpipes and welded in oxygen sensors so that the mixture can be adjusted to suit the altitude and the specialist fuel contestants are obliged to use by the SCTA. The motor build and gearbox work is under way, and we’ll keep you posted on progress right through to Speed Week 2018.