Here is a question -
How do you know when a Commando engine is not pulling as hard as it can ?
Because of the heavy crank, the motor always tends to spin-up at the same rate.
If you are trying to ride quicker up a mountain and the road twists and turns, it is not just a blast in top gear at full throttle.
You would normally race-change up and down through the gears. With higher overall gearing , you tend to wait longer for the revs to rise. The slides in your carburettor are often wide open and you might be using the main jets. The main jets are usually richer than the needles and needle jets, so the bike will not accelerate as fast as it would with the throttle partly closed, and the metering being done by the needles. The rate at which the needles' taper increases determine how quickly the mixture richens. If it richens too quick, the throtle response will be slower and your own response then makes the situation worse.
Under normal circumstances, most guys would not try using different taper needles. Speculating is never as good as actually trying.
My 850 Commando motor has as good throttle response as my short stroke 500cc Triumph motor ever had.
I use 6D Mikuni needles - the leanest - my overall gearing is absurdly high. With carburettor needles, most are the same diameter at the parallel part, the length changes to suit the diameter of carburettor - regardless of the brand of carburettor. My bike has Mk2 Amal carbs with Mikuni needles. I make my own needle jets out of brass hex using a combination of metric and number drills.
The needle jets and needles are critical for going faster.
When I first started racing the Seeley 850, It was quite funny. I felt my motor was gold-bricking - and it was. While I was riding the bike, it did not seem to matter what gear I used, the acceleration rate was always the same. When I raised the overall gearing the bike went faster. But close ratios and high overall gearing are very good. A standard gearbox is a handicap.
I would not normally say this, however back when I was racing regularly I alwars rode in Allpowers C grade races and I know what 'fast' is. In those days Kawasaki Z900s were the fastest - my Seeley 850 is faster. I think it is a bloody joke that something so horrible can be quick enough. It sat unraced for 20 years because I never believed in it.
