Harley Evo Breather Gear End Play

Mike has already installed a new, updated cam bearing into the left side crankcase. Next up is to check for correct Harley Evo breather gear end play. The stock Harley breather gear is made of a hard plastic. Correct end play is set with a spacer (or thick washer) that is located on the end of the breather gear. This spacer is also made of a hard plastic or nylon. The spacer is sold in a variety of thicknesses for achieving correct end play.

Mike demonstrates how to measure and check for proper Harley breather gear end play. With the new cam cover gasket temporarily set in position, Mike lays a metal straight edge across the breather gear spacer and cam cover gasket surfaces. While holding the straight edge in place, Mike makes his measurement with a feeler gauge. Now, it can be determined if a different size breather gear spacer will be needed. A Harley Evo breather gear that is set up too tightly will have excessive friction due to drag or binding. If the gear breaks, the resulting damage can be catastrophic—especially if debris finds its way into the oil pump.

It is important that the Harley Evo breather gear and the breather gear chamber have smooth surfaces. If the stock plastic breather gear surface is rough or marred, it should be replaced with a new gear. Aftermarket Harley Evo breather gears are available from S&S Cycle. The replacement gears are made of metal and use a metal spacer/washer. If a replacement gear has a tight fit, it can be corrected by lightly honing the breather gear chamber. Also, if the breather gear chamber is rough or marred, it can be cleaned up with a fine grit ball hone.

While the cam cover is still removed, Mike inspects the oil pump shaft circlip, the pinion gear, and the oil pump gear. The oil lines are also scrutinized over at this time.

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