The H-D© M8 engine has a problem with excessive oil consumption. This Trask Performance transmission top cover solves many of the problem causes by bleeding-off excessive crankcase pressures. This is done by using a one-way Boysen valve. The oil/air mist is better kept in the cam chest and the oil pump works more efficiently. Less air/oil mist will exit the engine through the head breathers. Reduced crankcase pressure also adds a little horsepower since the engine will rev more freely. Note: This CheckM8 transmission top cover will not solve the M8 oil transfer problem. H-D© has a pump seal service bulletin that addresses this problem.