Motorcycle Repair/Oil filter 1965 Honda CB72 250cc twin
When I removed the outer cover to access the oil filter, the shaft, filter and gear came away preferentially with the cover leaving the small drive chain dangling behind inside the clutch cover. My question is should this have happened as I am struggling to re-assemble without removing the entire clutch cover to gain easy access.
Further puzzling (to me at least) is that to remove the actual filter outer cover (behind the large circlip) it looks as though I would have to pull the shaft out anyway as the cover would not slide over the pin in the shaft that locates in the outer cover.
Many thanks for any advice, hope my mail makes sense!
Mal, the clutch cover/oil filter covers come in two sizes.. small hole and large hole. If your bike is all stock and built in 1965, then it should have the big hole cover and that does allow you to remove and replace the oil filter/chain without pulling the clutch cover off. It is impossible with the small hole versions.
Having the shaft come out with the outer cover is pretty common, as the combination of the shaft and the locating pin in the end of the shaft are more deeply seated than the engine crankcase mounting hole side.
The shaft should come out with a pull/twist as long as it was installed properly last time. I have seen where people don't recognize that the shaft pin needs to register in the recess in the outer cover and they just hammer the cover back on, causing damage to the cover.
As long as the filter is removed, clean it! This is another bit of blacksmithing, as the filter rotor cover must be knocked out from the back side with a screwdriver/shaft of some kind while being careful not to damage the shaft hole. Just remove the outer snap ring, then start tapping through the filter rotor hole towards the cover side in a circular pattern, so the cover comes off fairly evenly. Once the cover is off, then inspect the hole to be sure you didn't peen the edges of the hole over causing the shaft to bind on the distorted edge of the hole.
Carefully fish out the little o-ring which sits between the cover and rotor body, then start to scrub out all the dirt and debris inside the filter body and the cover. Clean it thoroughly then oil up the cover edges, install the o-ring and tap the cover back in place evenly. Install the snap ring. Oil the shaft and filter holes with oil and be sure that the whole filter assembly is able to easily spin on the shaft. The thrust washer goes against the outer cover so the pin doesn't dig a groove in the cover edge. You can use an oil can to help fill the filter body with some oil to help speed up the refilling process when the engine fires up.
Drape the filter chain on the filter body and then install it into the clutch cover hole. You will need to use a long scribe tool with 90 degree tip or a stiff piece of wire with a bent end so you can help the chain onto the crankshaft sprocket teeth while it was still on the filter. Slowly locate the shaft into the crankcase hole while the chain is still attached to the sprockets.
Ensure that the pin is located at 12 o'clock position so that the outer cover slides on to the shaft and the pin fits down into the recess in the cover. Put the long screw through the outer cover and start a few threads into the engine case threads to help center the filter cover on the clutch cover opening. Push the filter cover into the clutch cover opening with your hands, maintaining the screw hole alignments. You should be able to push it home with the flat of your hand in one quick slap. Install the remaining screws and you are done!
Often these filters have never been cleaned and are packed with dirt, debris and metallic bits so it is an important maintenance step which should be done every 5,000 miles or so depending upon how often the bike is driven and if there are metal pieces found in the old filter debris.
disregard how the thrust washer is drawn in this illustration, however. It must be placed on the outer end of the shaft, next to the pin.
I hope this all makes sense to you. You will feel better once the filter has been cleaned out and so will your engine!