Assembly is – of course – the reverse of removal.
Note: as there isn’t any oil circulation until the engine is running, lots and lots of oil is applied everywhere during re-assembly so that there won’t be un-lubricated metal-on-metal when it starts running. Additional lubrication with petroleum jelly was applied to some virgin metal surfaces which need more lubrication, this has a higher viscosity so will adhere for a bit longer during first start-up.
Starting with the off side crank case shell (the one with the studs in it) the crank and cam shafts go in. There are locating lugs in the bearing receivers and it’s important to line up the corresponding hole in the bearing shells when placing them. If you don’t the crankcase won’t shut properly.
The timing marks on the crank and cam gears must be aligned.
The oil pickup is fitted and the retaining bolt is secured.
The crank case halves are now ready to be joined, a thin bead of high temperature sealant was run round the mating surfaces.
Final check as the crank case halves are closed, the timing marks are still aligned.
The four 16mm crank case bolts can be put in finger tight at this point.
Next, the oil pump can be fitted to the end of the cam shaft. Start with a new paper gasket, this is dry fitted with no sealant.
The housing fits into the crank case first. There is a flat that goes at the top, next to the crank shaft – this ensures the oil galleries line up correctly.
The the inner rotor goes on next, it has a flat that goes onto the flat at the end of the cam shaft.
The outer rotor goes on last as it can be easily rotated to the point where it fits with the inner rotor.
The oil pump cover receives a new o-ring and some sealant round the outer edge before it is bolted on. In order to align these bolts with the oil pump and the crank case the pump housing may need to be rotated which is why the crank case bolts haven’t been tightened yet.
With the oil pump in place, the crank case bolts can now be tightened according to the sequence and torque settings in the manual.
The two crank shaft oil seals can now be fitted. The are a push fit but the tolerances are tight so use plenty of lubrication (also prevents them tearing when first running) and carefully drift them into place.
Now’s a good time to put the tappets in – I’m using new tappets as I have a new cam shaft. These are a tight fit and plenty of lubrication is necessary.
The cylinders had previously been lapped to the crank case so time to fit the pistons. With some light persuasion the gudgeon pins slide through the pistons and the con-rod little end bearings.
With the gudgeon pin mostly through the retaining circlip can be fitted. The gudgeon pin can then be pushed through until it seats on the clirclip at which point the other circlip can be fitted.
Next step will be to fit the heads.