HONDA CL350
Mark’s having issues with the CL’S oil filter…
Mark Haycock back with this classic machine.
The carbs should now be in operation so next on the list is normal service items and I generally start with the ignition system. As new pattern contact breaker points are reasonably priced at around a tenner for each set, it seemed a good idea to fit them, but we shall see what happened soon when I shall look at this in more detail.
But suffice to say, after a bit of attention the ignition seemed to produce some pretty strong sparks. The valve clearances on this engine are adjusted in a slightly unconventional way. In Photo 1 we see the contact breaker housing and I want you to look at the large hexagonal nut on the left-hand side. This is a locknut for the rocker shaft, which can be rotated using the screwdriver slot. The rocker itself is mounted on an eccentric portion of the shaft and this alters the valve clearance. In the past I have found the operation to be a bit fiddly as tightening the
locknut constantly altered the clearance, but this time it all worked perfectly well. Maybe it works better on engines which are not worn out. One point is that there are always two possible positions for the shaft to get the clearance you need, but only one is correct. The little punched line by the adjusting slot should face outwards.
Clearly I needed to put some oil in the engine as it had been drained, but I also wanted to take a look at the oil filter. I say take a look as this is a centrifugal design which needs cleaning out rather than replacing. The first thing is to undo three screws and remove the circular cover on the right-hand side of the engine. There is even a screwdriver slot to show you where to apply leverage to avoid damaging it, so what could be simpler? Lots of things as it turned out, and when I applied a bit more pressure, the edge of the cover broke off, much to my annoyance (Photo 2). Yes ok, with hindsight I should have had more patience and used penetrating oil on it, particularly as that cover costs £60 – except it has now been deleted, and sellers want (in my opinion) silly amounts for grotty second-hand items. But I had a brainwave! All I needed to do was to rotate the cover through 60º so that the missing bit did not show: except you cannot do that as the screws are not equidistant.
This sounds like a deliberate ploy by Honda to sell more covers, but it is not quite like that. To explain, let us take a look at the filter itself after the cover has finally been broken – I mean removed (Photo 3). It consists of a small drum, like a miniature washing machine and in a similar way it can rotate at high speed to fling the contents outwards by centrifugal force.
The purpose here though, is to separate particles of metal and dirt from oil. They are heavier and are flung outwards and pack together, sticking to the inside of the drum, just like clothes do in the washing machine on the spin cycle. What you are left with is a stiff grey paste, which needs to be cleaned out from time to time. To see what is inside, we use a ‘special tool’, which is simply a longish M6 screw which is screwed into the end plate (Photo 4) and used to pull it out. In my experience, this never happened in practice as I used to see a thick, ancient layer of gunk, but for the first time in my life I see one which is almost perfectly clean (Photo 5). Notice that the drum is
held on by a special Honda nut, rather like that we saw on my CB750K2 clutch. Also note that the lid is sealed by an O-ring and it fits with the ribs, fitting in between ridges cast into the drum. Now, as the drum is closed off at the inside end, the oil clearly needs to be able to get in and get out again after being cleaned, and that must be via the outer end.
And so it is: this is handled by the cover, and in Photo 6 we see a view from the inside. In the centre is a pipe and surrounding it is a hollow bush, known as the oil guide metal (which probably makes more sense in Japanese). The pipe extends into the body of the rotor and its purpose is to fire a jet of oil (which comes directly from the pump) into the filter. The ‘metal’ is, in fact, a mechanical seal. It is spring-loaded to be pressed against the rotor, thus creating a seal between the rotor and itself, bearing in mind that the rotor spins and the ‘metal’ is fixed. So the central part goes to the filter and the surrounding ring comes from it to the rest of the engine. The two cylindrical parts of the casting are hollow, forming the pipes to and from the filter, and they line up with holes and hence passageways in the right-hand engine cover. So it is vital that the oil filter cover is fixed in the correct place, hence the subtle spacing of the fixing holes.
You need to check, by the way, that the ‘metal’ slides freely, as otherwise oil can escape and mine was not that great so I took the lot to bits and in the process damaged the little wire circlip. After checking that an ordinary circlip will not work (Photo 7) because it obscures the seal, I was able to get a suitable substitute from Simply Bearings, which was fortunate as it is not now available as a Honda part.
Finally, sealing of the cover is done with a couple of O-rings, one in the crankcase cover hole and one on the oil filter cover (Photo 8), and it is best to replace them as there is a lot of oil flowing round here. One good point was that the broken bit of the filter cover was outside the O-rings so I could still run the engine with the damaged cover: maybe next time?