Navigator - splitting obstinate crankcases

Hi Chris,

You should be able to separate the crankcases if all the screws holding it together have been undone. 

You do not have to undo the crankshaft pinion or the camshafts. Or oil pump. These all stay with the timing side crankcase. As does the crankshaft. L/H  Camshaft lobes must be in the right position. Easiest if intermediate pinion is removed.

There are four screws that can be overlooked.

Two long cap screws are hidden under the back part of the timing cover gasket. The heads are at the bottom of two deep holes. You need quite a long hex key to reach these screw heads.

Two countersunk cap screws accessible between the two cylinder location holes. Short screws and not readily seen unless you look closely. May be obscured by T/S conrod.

With all screws removed, only gasket goo and resistance from the two locating dowels is stopping you.

Sharp blade, like a kitchen knife, gently hammered between the front or rear mounting bosses gets things going. Doesn't affect the sealing faces.

Or tapered wood wedges between the innermost cylinder studs, at their base. But careful not to bend cylinder studs.

Monday now, so you probably got there already.

Good luck.

Peter

I echo everything Peter says above.

The two hidden screws are in the timing chest, behind the crank, and in front of the gearbox.

And two more between the cylinders.

I then use a piece of 1" x1" wood (or similar size) & tap gently the l/hand opening in the crankcase towards the primary chaincase - then invert the motor and do the same where the sump plate was.

The Drive side crankcase should then come away off the roller bearing on the crankshaft - with the bearing outer in the case itself. If you meet resistance, then you have left a screw in somewhere.

For the next operation, I use two car axle stands, 2 planks of wood and a long drift made out of an old A/F box spanner. YOU MUST NOT HIT the end of the crank - EVER! to remove it.

Arrange the axle stands & planks of woof succ that the Timing side crankcase (complete with crank) is resting between the axle stands on the wood, with the crank hanging down. Put towels, etc under the crank to soften the fall when it lets go & gently (with a heat gun) heat the bearing boss. After a few minutes of heating, the crank (complete with bearing) will fall out under its own weight. If not, a gentle tap (using the drift) on the bearing inner will see it fall out.

Reassebly - use heat to replace the bearings - dont bash them in cold.

Use the Norton Twins Manual as your bible.