Improve engine capabilities, the mechanics are competing to redesign the components related to engine work, especially those related to combustion chamber so that engine performance increases. Among them is by modifying or changing the valve size and porting the IN and EX valves. The process of this research is done by means of standard engine data retrieval using dynotest test equipment, flowbench, and fuel testing. Then do the modification process by changing the valve diameter, while in the second data collection using the same test equipment. From the results of standard engine data retrieval, it will be compared with the modification engine data retrieval. The test results of the flowbench test equipment, standard airflow (cfm) data obtained from the intake hole channel reached 27.6 cfm at the opening of the valve or lift to 7 mm while from the intake hole channel that was ported and the change in valve diameter the results reached 41 cfm at valve opening or elevator to 7 mm. The results of the dynotest test use the standard maximum torque engine dynamometer which was reached 11.38 Nm at 3854 rpm and the maximum power reached 7.5 Hp at 7486 rpm while the data retrieval was modified after porting and changing the maximum torque valve diameter reaching 13.94 Nm at 3373 RPM and the maximum power reached 7.5 Hp at 8228 rpm, so the porting modification and change in valve diameter increases torque by 2.56 Nm while the power does not increase the power remains the same at 7.5 Hp is only different at 7486 rpm at standard while after modification achieved at 8228 rpm on the EFI Suzuki Nex motorbike engine. Based on the test results, the fuel consumption is a normal speed of 20-80 km / h when the engine is standard and in ported modifications. Then the standard data obtained from the normal speed of 20-80 km / h distance traveled is 66 km while after being modified from the same speed the distance traveled is 62.35 km.