How do you do a motor and gear box alignment using two dial gauge?

Answer 1

Crankshaft flywheel flange runout.

The crankshaft flywheel flange must be perpendicular to the axis of rotation of the crank with no permissible runout. Place a dial gauge on the bell housing and position the tip against the flywheel flange, parallel to the crank axis. (Perpendicular to the flange surface). Zero the gauge. Rotate the crank slowly by hand and watch for any movement. Any runout must be eliminated (because it will be compounded by the radius of the flywheel.)

Flywheel friction face and rim face runout.

With the flywheel now mounted to the crank, Place a dial gauge (magnetic clamp or mechanical clamp) to the bell housing and point the dial gauge perpendicular to the clutch friction face on the flywheel. Slowly rotate the crank and check for variation (runout). Maximum permissible runout is 0.01mm per 10mm of flywheel radius. Thus for a typical 300mm dia flywheel, max runout is 0.15mm (0.006"). (Runout here could cause rapid wear of the clutch splines or the driven plate breaking away from the splined hub due to continual flexing.)

Reposition the dial gauge to point at a smooth piece of the flywheel near the starter gear teeth (rim), once again parallel to the direction of the crank. Slowly rotate the crank and note any runout or warp in the flywheel. The same maximum permissible runout applies here.

Bellhousing (gearbox) runout

Repeat the exercise with the dial gauge clamped to the flywheel/clutch assembly pointing out (radially) to the bell housing locating the dial gauge point on the machined face of the bell housing that locates the gearbox. (At right angles to crank direction). Check for radial run out. Maximum permissible runout is 0.20mm or 0.008".