Tech Tips: Briggs & Stratton LO206 – Setting the Valve Lash
For many racers who are new to our sport, learning and understanding certain maintenance procedures for either their kart or for the engine can be a daunting task. Briggs Racing, the American kart engine manufacturer, has made it a little easier for those unfamiliar with key aspects of engine preservation by producing tech videos to walk their racers through some of the primary engine maintenance programs. The focus is to ensure that each racer is getting the full amount of power available when they hit the track.
One item that racers should pay attention to is ‘Valve Lash’. The intake and exhaust valves control the flow of fuel-air mixture, or vapor, into the combustion chamber and the flow of exhaust gases as they are forced out of the engine. Faulty or dirty valves may stick, which may lead to developing pits, cracks or grooves that can cause the engine to lose power. The valve movement is controlled by the rocker arm and the gap between the rocker arm and the valve tappet (top of the valve) is called the ‘valve lash’. When measured on a cold engine using a feeler gauge, valve lash for the Briggs LO206 engine should be .003-.004 inches on both the intake and exhaust exhaust side. As the engine heats up, this gap will open and you will get the max lift and duration.
“Within the first hour of use, the valve lash will likely open as the first heat cycles relieve the manufacturing stresses in the valve train,” commented Dave Klaus of Briggs Racing. “After resetting, it is something to review every hour or two of track time. I personally check it going into every race weekend for the simple fact that a few thousands of extra lash is giving away lift and cam duration. We at Briggs Racing run engines in 40-60 hour cycle tests that maintain their initial setting. To me, it’s just something to do as part of my routine.”
Below is a video of how to check the ‘Valve Lash’ on a Briggs engine, be it an LO206, Animal, or World Formula. You can find more videos at the Briggs Racing video section of their website.