There
are many crankcases around which have the front main bearing retaining lip broken or
cracked. Without this lip the crankshaft cannot be held in the fore / aft
direction and is allowed to float. This puts a sideways strain on the pistons
and connecting rods and, when the foot is applied to the clutch pedal, the
crankshaft is driven forwards by the pressure on the clutch, distorting the
front bearing retaining plate and altering the mesh of the crankshaft to
camshaft gears. Altogether an undesirable situation.
All is not lost.
Those of you who have the excellent 750 Motor club publication, the Austin
Seven Companion, will find a design of a tool to remove the broken lip to be
replaced by a retaining plate which clamps the front bearing. The design
uses 1" steam pipe which is not so readily available these days so I set
about modifying the design to use materials available today.
You
will see from the picture that the tool consists of two larger diameter bosses
turned to fit the inner
race of both the front and rear main bearings. these are separated by a length
of steel rod. The cutters were made from broken HSS drills of about 8mm in
diameter.
To
use the cutter the front main bearings are inserted in the housing and held by
the original front retaining plate. The front end of the cutter is fed into the
bearing the rear main bearing is slid into place and the top end of the cutting
tool is slipped into the rear bearing which is prevented from falling down by a
little insulation tape wound around the lower end of the boss. In my case I
arranged the tool so that an old socket spanner could be slipped over the end
and a socket ratchet used to wind the cutters round.
Simply
apply a little pressure whilst winding the cutters and in a vary short space of
time the new surface is cut so that a new retaining plate can be used.
The
additional retaining plate is a front bearing retaining plate with the bolt
holes countersunk.
Using the original front retaining plate drill out the threaded fixing holes
right through into the crankcase keeping the drill as vertical as possible. To
assemble insert the new retaining plate and fixing bolts from inside the
crankcase. insert the crankshaft and slide on the two front main bearings. Using
nuts and locking washers bolt up the original outer retaining plate. It may be
necessary to use a shim to pre-load the bearings. If you follow the description
in the Austin Seven Companion using this tool you should have little difficulty.
Please feel free to discuss this repair if you need to.
