A bog-stock KTM SMT 990 came through the workshop recently; the owner was complaining of rough running at low speeds and a general lack of power from the engine. Now getting horsepower out of one of these big KTM V-twin engines is fairly straightforward, but does not necessarily make for a smooth delivery.
So we decided to approach this bike in two stages; firstly, sort out the lumpiness and rough running. The first job was to eliminate the lambda sensor, because as ever it was the root cause of most of the problems down low. Then, plugging into the ECU we adjusted the throttle map to ‘dial in’ specifically the amount of squirt the engine produces for each percent of throttle valve opening, dramatically smoothing the low-down delivery.
Next step is the mid-range, as the owner still wants a little more. Some open cans will be on his shopping list, and now the power delivery is consistent at all throttle positions we can be a little more extravagant with the fuelling and ignition maps, which will heap huge rewards in terms of mid-rpm power and torque.