ON WHAT was the hottest April day since 1949, the Visordown powers that be (editor Al) decided that there was no better idea than heading to the hot and sweaty confines of Big CC racing.
But even the 27-degree heatwave wasn’t enough to quell my spirits as we headed inside to dyno our new long termers. First up was Al’s Suzuki GSX-S750. I arrived at Big CC to find him undressing the naked bike even further, in order to get to the ECU.
The 750 screamed into life on the dyno, and as Big CC’s Sean Mills performed a number of runs I was thankful for my earplugs. I was taken aback at just how loud a motorbike bouncing off the limiter could be in such a small space (not exactly rocket science, I know).
After checking out the GSX-S’s results - 100bhp, 53 ft lbs of torque and a tad on the fuel rich side – it was the Duke’s turn.
She sat proud on the dyno, but the reading kept cutting out after 5,000rpm - weird. Turns out that Al had connected the dyno tacho sensor to the secondary spark plug connector (the 690 has two because of its giant combustion chamber apparently), and it seems to stop firing over 5k. With no ignition feed, the dyno couldn't measure torque, or power against engine revs. Switching the sensor feed to the main central spark plug soon fixed that though, and we were back in action.
She didn’t sound half as impressive as the mighty four-cylinder Suzuki, but ear protection was still definitely required. And after a couple of runs, results were up: 71.89hp and 52.11ft-lbs – not bad at all, given that KTM claims 73hp and 54.58ft-lbs (and that’s at the crank!) Even better, the air/fuel ratio chart shows the 690 motor is almost perfectly fuelled all the way through the rev range, with no rich or lean spots anywhere. Good job KTM – especially on such a highly-tuned big single cylinder lump.
The Duke is off to KTM UK for its first, 600-mile service next week. And while they’re at it, I’ve asked the mechanics to add a few trick bits.