Main bearings
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The end float was checked on the rear bearing and set to .0003 inch by grinding the surface of both thrust flanges with coarse paste on some glass. The end  float is measured with a feeler gauge between the shell thrust face and the crank flywheel flange. If it is not 3 thou the shaft might seize when hot as the aluminium bearing housing expands. After a trial fit with torqued  up  bolts and some turning of the shaft some high spots were noted and ground down again. Turn the shaft by fitting the starter dog. Note do not exceed 80lbs feet torque as the dog may break. After 3 attempts I was happy. Note all traces of paste were washed off as the soft white metal tends to absorb them. There are many bearings that have oversize thrusts (10thou) so check end float. Obviously oversize bearings will not fit in a standard shaft but they can be ground down. An oversize shaft will have a bit too much end float with standard bearings.

In the absence of 30 thou oversize main shells I cut the flanges off some rears to make these.


I check the shaft turns when the bolts are torqued up, slowly tighten them in turn evenly to see which bearing is binding, as usually it binds with a reground shaft and new bearings. Then turn the shaft about 10 revolutions and remove it for examination. you can usually see a shiny bit where the bearing is grabbing. Often the interference is on the width of the bearing caused by the filet radius to the web. A smooth file will rectify the situation. when everything is turning nicely clean all the oil off. Note the oil seal wear ring on this shaft that needs to be avoided by offsetting the new seal.

This shows the use of Plastigauge to measure the main bearing clearance. The clearance is about .00035 Inch. the wire of plastic is squeezed flat when you torque up the crankcase bolts. The width of resultant smear is then measured. Note the shaft and bearing must be free of oil and must not be turned.

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