Somebody once told me in production racing a single carb 650 triumph could be quicker around a really twisty circuit than a twin carb
If true maybe the single carb bike is pulling in a better mixture at lower revs and pulling harder
Or it's getting onto a bigger carb opening/slide position quicker???
If you are tuning a bike for racing, the needle and needle jet are of critical importance. A single carb is easier to get right. I have had Triumph 650s with both single and twin carbs. It was back when I did not know what was important, and my bikes all performed much the same as each other. These days I race using methanol and half a thou difference in needle jet internal diameter ,is the difference between fast and slow. When using petrol that would be a quarter of a thou. To tune and fit that requirement would be much easier with a single carb. If I was doing it, I would make the needle jet and use a reamer and a flow meter to progressively increase the internal diameter, until the bike really has get up and go.
The shape of the needle affects the rate at which you can open the throttle. I use the leanest needles and feed the throttle on in a controlled fashion. The bike accelerates much faster that way. Normally the needles are probably designed for average riders who are heavy-handed. When you are above 1/3rd throttle with a normal needle, the mixture is usually a bit too rich to get the best power. But if you use lean needles, and you whack the throttle open, you might get a gasp. On a race bike,we don't often do that- smooth riding is more important.
Some guys are slow in corners and wait until the bike is upright and pointed before giving it the berries. For me, the next straight begins as soon as I enter the preceding corner, With a Commando, you need to come out of the corners much faster, because it hasn't got enough power to win a drag race.
When I was young I used to race my Triton in Allpowers, against four cylinder bikes and two strokes - they all take different lines in corners - mostly out wide. The Seeley frame is a major advantage, but Featherbeds are OK when the motor is well forward.
