Strange problem - easy solution - still not happy.

Hi everyone.
Good luck and happy riding for the coming year.
My bike has been out most days as the weather hasn't been too bad over the winter.
Only got the bus twice. Woo hoo

Triumph 900 1996.

Anyway here's my problem..

When the bike is on its side stand, there is a very slow drip of oil coming from around the chain cover. It generally drips down from below the gear shifter, this it the lowest point so it runs there.
I've replaced the gasket had a good clean and look and spotted no cracks.
Still leaking, about a tumbler worth in 3 months.

However on its centre stand no leak.
The oil level seems to make do difference at all to the leak or the amount.

Thanks for any suggestions.
Jimi

 

Thanks pistonbloke, good suggestion, but the oil level is going down also.

Thanks Richard I'll look into the drive sprocket seal.

Cheers I'll update when I've looked.
It could be Easter hols before I get a look though.