This guide assumes that you have removed the radiator and cooling fan. This procedure can be done with the motor in the frame and is the same for both 500 and 650 variants, though the 500 camshaft protrudes through the holder while the 650 camshaft end is not visible (see the differences here).
The camshaft holder sits at the front of the engine, unsurprisingly around the end of the camshaft:
650 variants (the bolts have already been removed in this photo):
If the tacho cable is still attached remove it; it should be held in by a single bolt:
The bolt is probably rather stuck unless someone has replaced it; often the easiest way to get it off is to use locking pliers (also known as vise grips) and replace it with a hex headed bolt for an easier time getting it off next time:
This one has been mangled a bit and was unable to be removed easily with a screwdriver:
The tacho cable end should come out easily now:
If you look in where you just removed the cable from you can see the flat peg that drives the tacho cable:
Now you should be looking at this – oil leak evident from around the seal:
If you have a 650 you won’t see the camshaft end, just the flat plug in it’s place. On the 500s, if the is a fan bolt and washers still in place on the end remove them:
Grab a 8mm socket:
There are four 6x28mm flange bolts holding it in – part number 96001-0602800 (eBay US, eBay AU, eBay UK, previously 96000-0602800 and 90006-413-000).
Now carefully pull the camshaft holder away – don’t try to twist it as there’s a steel collar joining the block and the holder so you won’t be able to get rotational movement until you clear that. If the holder comes free a little ways and is then difficult to remove further:
…rotate the engine by hand while pulling the holder and it should come away more easily:
Once removed you should see the end of the camshaft – the example photo is from a CX500:
Here’s what you will see with a 650:
There’s a collar and O-ring as mentioned above; make sure you don’t lose them:
The collar or dowel is part number 15155-300-000 (eBay US, eBay UK, eBay AU) and the O-ring is part number 91301-268-020 (eBay US, eBay AU, eBay UK) – 13.6×2.4mm.
The camshaft holder removed – a CX500/GL500 one pictured here:
