Berryman B-12 Chemtool Total Combustion Cleaning Kit (part #2610) is designed for use in gasoline engines that generate manifold vacuum and have serviceable way into that system. Unfortunately, that is not always the case with motorcycles. With carbureted engines, some people have elected to slowly pour such products into the carb. Doing so is effective but also increases the risk of hydrolocking the engine. An alternative product to consider is the Berryman B-12 Chemtool Total Fuel System Clean-Up (part #2616). It is the strongest fuel additive we make and will clean everything from the fuel tank to the combustion chambers. It will also help with emissions by cleaning the fuel injectors or carburetor for optimized fuel delivery (which can lower HCs) and cleaning the combustion chambers for more thorough burning of fuel (which can lower HCs, CO, and NOx). Berryman Emission Pass Protection (part #0212) does much of what the 2616 does, including cleaning the fuel injectors or carburetor, and has an extra additive to further reduce NOx emissions. However, it does not clean the combustion chambers as thoroughly as 2616 does. The best bet is to try the 2610 if you think you’re just looking at dirty combustion chambers. If the issue is more complicated, though, then consider running the 2616 through the fuel system. If that alone is not enough, then you likely have bigger problems (faulty fuel pump, bad carb or injector, etc.). While following up with the 0212 might help mask those in an emissions test, it will not have solved the underlying issue.