After removing some of the external ancillaries such as the fuel pump and the flywheel (with the assistance of Super Crack Ultra, heat, an impact wrench and a breaker bar) and leaving the oil to drain I got stuck into dismantling the engine.
Firstly I got the the jelly moulds off to drain the residual oil and reveal the valve gear.
At this point it became clear why the engine wasn’t fully turning over: one of the head studs on the off side cylinder had sheared at the bolt.
As this bolt also secures the rocker pivot axle it meant the exhaust valve wasn’t able to operate fully thus jamming the push rod, thus jamming the camshaft, thus jamming the crank. Fortunately it doesn’t look like any damage has been done to parts I wasn’t planning on replacing anyway.
With the head stud bolts and the oil feed pipes removed, the barrels and heads came away from the crank case. Whilst the near side head and barrel separated by hand the same wasn’t true of the off side (home of the malfunctioning valve) – despite application of my not inconsiderable bulk via a pry bar!
I applied a large libation of penetrating fluids and left it to marinate whilst I moved on to the crank case.
The crank case splits in half down the vertical longitudinal axis and is held together by four large (14mm) bolts in the centre and half a dozen smaller (11mm) bolts round the outside. However, there are some items that straddle the join so they need to be removed before starting on the crank case bolts.
The oil cooler needs to come off the front of the engine, firstly remove the retaining bolt above the nose of the crank shaft where the fan mounts. Then carefully remove the union bolts and ease the pipes out of the crank case.
Round the back there are a set of five 12mm bolts that hold the cap on the oil pump and below that there are two 8mm bolts that hold the oil strainer in place in the sump.
Work round the outside removing the 11mm crank case bolts – some of which are on through nuts and some on studs so make sure you check which one you’re dealing with.
Buried under the surface gunk I found one of the nuts had a washer with a long tab – not sure why but that was the only item of note.
Next up there are the four large bolts, two on each side, that go through next to the crank bearings. With those removed the crank case separates easily.
At this point it’s worth rotating the crank and looking out for the timing marks and seeing how they appear when aligned.
The timing marks are small lines marked into the gears under certain teeth. The key one (and easiest to spot) is on the crank and, when at the timing point, it will align with the edge of the crank case half at 6 o’clock.
The timing marks on the camshaft are harder to spot but there are two of them, one on each of the teeth either side of the space into which the crank timing tooth fits.
With the crankcase separated the crank and camshaft stay in the off side half and require minimal coaxing to come free.
In the time it had taken to strip the crank case the penetrating fluids had worked their magic on the off side barrel and head and they were reluctantly persuaded to separate.
That’s now the main disassembly complete and with the parts labelled and stashed away in boxes it’s time to call it a day,
Other posts in this series:
- Engine tear down
- Crank case strip down
- Valve removal