Spa Treatment...part three
Dyno Day
John Newman
Europe's premier classic bike meeting comes to Spa-Francorchamps circuit at the beginning of July. Andy and Nick, from Moll Springs Motorcycles, have been working on three bikes which will be going to the event. The
exclusive Triumph/Greeves with the three cylinder Trident engine. A 1981 BMW RT1075. An early 1970s XS650 Yamaha, now a 750, the engine of which used to live in a classic racing sidecar.
Spa-Francorshamps is a fast 7km circuit with sections named to resonate with car and motorcycle race history. The chicane before the short start/finish straight, which used to be the "Bus Stop". La Source hairpin. Eau Rouge/Radillon, flat out swervery before hitting the longest straight section. The bikes' riders will be looking to get the best performance from the machines.
Andy and Nick needed to determine if the engines they'd set up were putting out the intended power and torque. So they booked a session on a motorcycle dyno at Swinton Motorcycles, a tuning and repair workshop.
Ashley Law, the workshop's owner, made his mark on the racing scene in the 90s and early 00s. Ashley was a regular winner and podium placed rider who concentrated on the real road races, including the TT. His major win came in 2001 at the Ulster Grand Prix. He won the 250 race and then brought his 250 Honda into a courageous sixth place in the main Ulster Grand Prix. He was then persuaded to ride a Moto Guzzi in the TT in 2002, as part of the Guzzi centenary celebrations. A tough gig around the mountain circuit.
Ashley retired from racing after this and started Swinton Motorcycles. And this was where we gathered on a dull drizzly morning so that he and the dyno could assess the state of tune of the three bikes. He would tell Andy and Nick what engine work would be required in the weeks leading up to the departure for Spa.
A motorcycle dyno (short for dynamometer) is a rolling road linked to a computer-based programme. It measures torque, power, rpm, and top speed. The motorcycle tuner/technician uses it to determine what's needed to bring the engine to peak performance. The BMW and Yamaha were at last year's Spa meeting and had been stabled at Moll Springs since then, with the BMW undergoing extensive engine work.
Andy and Nick had spent a couple of days sorting out the timing and setting up the carburettors on the XS Yamaha. The real unknown quantity was the Triumph/Greeves. Andy had intended road testing it the previous day, but the weather was wet and cold. Despite months of engine rebuilding and problem-solving, they'd have to make do... with a spin around the industrial estate and running the engine in the workshop. This would leave the bike untried at anything approaching full power.
BMW
The first bike offered up to the dyno. Strapped down like a victim prepared for some terrible torture. Which is what a dyno session can turn about to be, depending on the bike owners' expectations and the information the computer screen throws up.
Ashley warmed up the engine before starting to increase the revs towards its redline of 7,000. The noise of a bike engine as it touches red before it is throttled down can be nerve-jangling. The first 'run' showed it running rich on the main jet, so Nick reached for the straight pipe they intend to run at Spa. A larger main jet had been fitted, so running a different end pipe could help the engine to run leaner, and so it proved.
An extra 2hp improvement showed at the top end. 10ft lb additional torque showed on the chart/screen from 3,600 to 6,400 revs, giving a top speed reading of 123mph. Smiles all round. Ashley said that the engine wanted to run towards 8,000 rpm and that peak power was being reached in fifth gear rather than sixth.
Gratifying. No surprise, though, as the engine has had a lot of attention, including special cam and valves, titanium can followers and a balanced crank. Andrew, the bike's owner and rider, is a tall man. He commissioned Malarkey Engineering,
who we recently featured, to remodel the subframe and made the riding position more comfortable.
Grumph
The Greeves/Triumph was 'stripped for action'. Devoid of the fuel tank, fairing and seat, so Nick had to hold aloft the oval fuel container like a paramedic attending a patient. I felt nervous, so I could only imagine what was going on in Andy's head. No worries. A satisfying 57bhp at the rear wheel. And the Trident could rev comfortably beyond 7,000, giving an impressive speed reading of 120mph. In third gear!
Andy and Nick have ordered slightly larger main jets for the old Amal carburettors that they'll stick with. They'll return the bike to the dyno to see if 8,000 revs is achievable and what the reading gives them for top speed.
Yamaha
Bike number three, the striking yellow and black Yamaha. Andy and Nick's work on setting up the timing and carburettors over the past couple of days looked like it had paid off. But, unfortunately, the old ignition system 'crashed' the computer because of incompatibility. Though not before a 50bhp reading at 8,000rpm had been attained. The dyno run also identified a clutch that was slipping and grabbing. But a new set of plates and stronger springs should cure this.
No major work to do now. Apart from a photo session when the Triumph Greeves is clad with fairing seat and transfers. The next time I'll meet the bikes and their riders will be at the circuit at the end of June.
It's just been announced that Bradley Smith will be at the Spa Bikers' Classic. He's the Moto GP rider for the Monster Yamaha Tech 3 team, and usually a front-runner. He'll be there with crew chief, Belgian Guy Coulon. Smith will be riding a Yamaha ROC YZR 500 2-stroke, which competed in the 1993 world championship rounds. This will be Smith's final year with Yamaha before transferring to the new KTM team in 2017.
Comments
14/06/16 Yes please would love to have one
14/06/16 now this looks like a proper bike
14/06/16 Very nice!
14/06/16 nice triton
14/06/16 Not the best set up in Tri/Greeves with those forks ,I would have gone for Featherbed frame Norton forks lower better handling,I think the BM is my favourite to go the pace
15/06/16 Norton has been done to death
14/06/16 Grumph, Grumph, Grumph, Grumph.
Grumph, Grumph, Grumph, Grumph.
Grumph ....... Glorious GRUMPH!
(trad).
(Also available in Spam) ...
15/06/06 helped with construction of a Tricati in sixties using 250 Ducati frame and T100 engine
15/06/16 Brilliant
15/06/16 Smashing British bike
16/06/16 Nice ride
16/06/16 We like that!
16/06/16 YES it's a (modded) Greeves frame with a Trident engine!
16/06/16 Engineering at its best
16/06/16 Sweet
17/06/16 Different,but very nice
EN