I will provide a bank account at the end of this so you can all convert your commiseration into contributions to my rebuild fund ;-)
Meanwhile, life goes on. After two weeks in Zim I was raring to finish this.
It took another two weeks after our return before the new pump arrived; with its removal and replacement, the workshop manual recommends replacing all the related seals and O-rings (7 items in total) as well. To my mind, Honda should really include them as a kit with the pump, as BMW typically does on their car parts (can't speak for their bikes). Since Honda SA does not stock them, you have to wait for three weeks if you forget one.
It only took about 2 hours to strip off everything so carefully assembled before, until just the centre casing was left.
The two halves are held together with 5-off M8 plus 2-off M6 bolts on the LHS, and 7-off M8 plus 3-off M6 bolts on the RHS.
There are three prying points to split the engine casings, but the two dowels on my engine were a bit corroded and required some encouragement to part company. A good idea I saw on the internet was hinging two wooden battens into an X like pruning shears, and using this as a lever to open the casing through the opening for the cylinder.
The gear selector shift cam plate needs to be in Neutral for the lobes to fit through the casing as well.
Finally all is laid bare.
For the mileage on the engine, there was surprisingly little debris on the strainer (it's not accessible from outside the engine).
The wear pattern on the inside of the crank casings (red arrow) showed signs of uneven wear- resonance, perhaps? I scoured them down carefully with a Scotchbrite pad and some scouring paste. Tolerances are tight here, and the bearing surfaces are soft, while the shafts are specially hardened.
The casing is actually double-walled (how do they cast that?!), with oil pumped directly into the cavity from the oil pump via a T-tube. From there it is fed through the radial holes in the main bearings into the crankshaft and through its oil passages into the big-end bearings.
The crank, being hardened, still looked fine, but I was recommended to just clean its contact surfaces off with a scouring pad, too. The main journals in the casings still looked good too, with no obvious signs of wear.
Not the same could be said for the conrod's white metal bearings, once the muck had been cleaned out.
Detail of bearing halves - from what I could find on the internet, this looked like erosion damage (see notes at end of post).
With all the gunge emanating from the journals, I removed the welsh plugs as recommended by Superfoxi and blasted the oil passages with carburettor cleaner. I'm not convinced that it necessary to remove the plugs as the carb cleaner's long nozzle can be pushed a long way down the oil channels, and the solvent seems to work quite well.
To make sure of the condition of the crankshaft, conrods and bearings I took the whole lot over to the engineering shop that had done the cylinders to measure everything up. They confirmed that the crank and conrods were still within spec, and that the bearings were due for replacement.
There are two codes for the casings and crankshaft interfaces to indicate which end of the tolerance range they are on. There are three viable crankpin bearing sizes and two options for the main bearings, indicated by colour codes. It's better to measure accurately to be sure that the right bearings are ordered: another three week wait to import these!
In retrospect, I could have ended up with bearing problems within a few tens of thousands of km had I not been forced to open the engine casing, so there was a silver lining to the cracked oil pump saga, after all!
There are two oil jets below the cylinder apertures, which spray oil on the inside of the pistons and cylinders. It's a good idea to clean them too. And replace two more O-rings.
Since the final drive axle's bearing can only be removed from the inside, and is exposed to a lot of strain from the long and heavy chain, it seemed logical to replace this also.
Although this bearing was still in good condition, the main shaft bearing was noisy, and the countershaft bearing alongside it had a grating sound. Sigh - another visit to Honda for parts. It seems that motorcycle bearings just aren't readily available from specialised bearing shops, apart from the wheel bearings.
The gearbox assembly has to be removed to access the final drive bearing. The three shafts can be pulled out without taking them apart. Fortunately.
Tapping out the double row final drive bearing with a socket turned out to be quite easy, and replacing it was not difficult either. No freezing required. Same for the other two ball bearings.
This was also an opportunity to see how the neutral indicator switch operates (I've always wondered): this is the spring-loaded contact ...
...which is grounded when it's aligned with the contact of the shifter drum when the gears are disengaged:
Presumably, sequential / concentric contacts are used for engines where every gear is indicated. A WORD ON BEARINGS
A number of different bearing types are used in the engine, the choice being determined by the type of load and available space.
Since huge forces are transferred by the conrods, they require a large contact area in a confined space. Hence white metal bearings (journal bearings), which are only 1.5mm thick. The actual load is borne by a layer of lubricant forced in between the shaft and the bearing by the oil pump (this type is known as hydrostatic). This film also provides damping, a function not available from anti-friction (ball) bearings.
The camshafts, piston crown and gudgeon pins are sprayed with oil, and rely on the rotation of the shaft relative to the bearing to create a wave of lubricant between the rotating surfaces (hydrodynamic type). In the close-up photo below, you can see the plain bearing that is press-fitted in to the crown of the piston; the conrod top end is case-hardened. Both of theses interfaces are only subjected to a rocking motion with the piston movement, so there is considerably less friction wear.
Needle bearings spread the load over a larger contact area (compared to ball bearings of the same size), allowing for a smaller cross section, particularly if the shaft is placed in direct contact with the needles, as done in the clutch and flywheel. This does require special hardening of the shaft, and special diamond cutters are required if you ever have to machine them.
The final drive bearing is exposed to both radial and axial forces due to the eccentric load on the drive sprocket. Deep groove double bearings are usually fitted for such applications.
I contacted a few tribologists regarding the wear pattern on the crankshaft bearings, and got this reply from Sandy Polak, consulting engineer (UK) on my enquiry:I suspect this is cavitation erosion damage. I deduce this from the radial patterns. It looks like it has only penetrated the thin "overlay" layer. This layer is soft and often eventually suffers cavitation damage on highly rated engines.
If it is cavitation, it could be caused by low oil pressure in the engine. I guess that also if you are at high altitude (much of South Africa is at 1500 to 2000 m above sea level), the lower atmospheric pressure could also have a small effect on the risk of cavitation.
The low oil pressure comment makes sense: when your engine uses oil, there are times when you run the level down low and sometimes I over-filled before long trips. This probably contributed to the wear rate, even though my oil pressure light never came on whilst riding.