Scooterotica

Before I take my Lambretta engine apart would some of you kind souls just confirm my suspicions that the drive side oil seal is failing/has failed:-
On an 80 mile round trip about 500mls of gear oil was lost.
There is no sign of gear oil residue in the crank area or inside the piston.
The B8ES plug has a medium brown colour.
Smoke was observed coming from the exhaust during strong acceleration only.
The scoot starts well from cold and hot.
There is no appreciable decline in performance.
There is no oil in the rear hub.
The breather is clear.
It is an Indian engine and I suspect that although the seal may not have blown the retaining plate is alloy and has warped a little.

Your Question had the answer
"On an 80 mile round trip about 500mls of gear oil was lost".

yeah, if your gearbox is running dry in only 80 miles, it's time to strip the mother down.

As you said, guessed it myself. Stripped it down today, congealed goo on the driveside crank web, nice puddle of gear oil in bottom of crankcase. Magneto side inner oil seal blown and Mag side bearing f****d.
Ordered Viton seals from MB. Got bearings, rebuild tomorrow.
Thanks anyway guys.