klr650 rotorThe KLR650 rotor has a single tooth to trigger the crank position sensor. It works well for the current setup because all it does is igniting the air fuel mixture via the spark plug. It does that a couple degrees before top dead center on the compression stroke. 360 degrees later it does it again on the exhaust stroke. It is call wasted spark.

The Engine Management System (EMS or ECU) is the heart of the fuel injection system. Its main purpose is to deliver the right amount of fuel and ignite the fuel air mixture at exactly the right moment. To help the ECU in its precise execution a trigger wheel which will provide a higher resolution than the existing KLR650 rotor with its one tooth trigger will be required.

Fitting an additional trigger wheel would require extensive modification so it was decided to machine the original tooth on the KLR650 rotor down to a width of 5 mm. Eleven more equally spaced 5 mm wide teeth were added to provide a total of 12 teeth. This will allow for 30 degree resolution between teeth. If a higher resolution is required another 12 teeth can be added to make it 24. Then the KLR650 rotor would support 15 degrees resolution.

To understand resolution versus trigger wheel teeth better lets first look at counting pennies. Yes you have read correct, counting pennies will help you understand how an Engine Management System work? The penny idea came from a friend of mine that once tried to run me over with his KLR. Neither him nor I knows why but he tried.

Wasted Spark

In a wasted spark setup the ECU fires the spark plug every time before the piston gets to TDC. Once to ignite the mixture and at overlap. Nothing happens if the spark plug is fired at overlap and therefore it is wasted. Hence the term Wasted Spark.