Hi Roger,
Presuming your bike is a swinging arm model and if you have the earlier chaincase cover one of the securing screws doubles as a level plug. Another doubles as a drain plug. Both of these screws should be fitted with a fibre washer or some type of oil seal.
If none of your screws are fitted with seals look on the inside of your cover if it's off the bike and it should be obvious which two I'm referring to. If it's still on the bike remove the screws (then replace them) one at a time to obtain the same answer.
Beezageezauk.