Custom Dirt Bike & Motorcycle Air to Fuel tester (Dyno)

You must build a custom exhaust clamp if you are going to test single cylinder dirt bikes or motorcycles. This is a short video to show you the homemade rig’s we built to test dirt bikes and motorcycles. Using off the shelf plumbing parts we built an automotive exhaust clamp and a motorcycle exhaust clamp that fits deep into the exhaust pipe. Both exhaust clamps are connected to an innovate MTX-L AFR (Air Fuel Ratio) gauge and wide band O2 sensors.

The reason you need to build a custom exhaust clamp for dirt bikes is because the single cylinder bikes scavenge air from outside the exhaust causing the O2 sensors to report a lean condition. Getting the 3/8 copper pipe deep into the exhaust allows for a much better and more consistent and real reading.

Both exhaust clamps are built using 1” plumbing pipe and the smaller pipes are all 3/8”. The float bowl measuring plug is just a rubber stopper from the hardware store, a nylon elbow and some gas line. Always start with a clean carburetor and the correct float levels and start working with the AFR from there.