The Importance of Timing Sprocket Alignment

The Importance of Timing Sprocket Alignment
When assembling an engine, one of the most overlooked items is the timing chain sprocket alignment. The upper and lower gears should be installed and alignment checked with a straight edge. I have seen them as far as .020 ̋ off. I allow the upper sprocket to be “proud” by half the thrust clearance when checking with the crank pushed toward the rear. As the crank floats from the oil pressure, it will be centered. To adjust this, simply remove material from the sprocket that needs adjusting. I do it on a rotary table in the milling machine, spinning the sprocket on the table and using an end mill. On some, the top sprocket can be machined for a Torrington bearing or thrust washer at this time, while simultaneously correcting misalignment. Proper timing chain alignment will give a longer service life.

Ron Flood
Cedar Machine Service
North Branch, MN
November, 2015