Jet 200 spewing oil from chain case

Try as I might I can,t find a : how to do a leak down check : link or info on here.
Would like to check if seals etc ok before pulling apart further.
I have oil coming from the clutch arm rod hole in the chaincase plus from around the gear shaft which has run down the casing and thrown onto the sidewall of rear tyre initial thought was blown rear bearing seal.
Rear shoes dry as is inside rear hub thankfully as was out on a ride when I noticed at a petrol station the state of the sidewall of my tyre.
Checked oil level in g/box at petrol station and was just below the upper level check bung so continued on my way all bit it carefully..
Drained just over 1/2 ltr out when drained the g/box the next day and stripped down to investigate cause.
Aware it could be blocked air vent in the fill plug ( yet to check this ) .
Condition of engine unknown to me as I bought as a running roadworthy scooter last year.
Been wanting an excuse to have a nose inside and carry out a few mods along the way.
Would like to check if seals etc ok before pulling apart further.
I have oil coming from the clutch arm rod hole in the chaincase plus from around the gear shaft which has run down the casing and thrown onto the sidewall of rear tyre initial thought was blown rear bearing seal.
Rear shoes dry as is inside rear hub thankfully as was out on a ride when I noticed at a petrol station the state of the sidewall of my tyre.
Checked oil level in g/box at petrol station and was just below the upper level check bung so continued on my way all bit it carefully..
Drained just over 1/2 ltr out when drained the g/box the next day and stripped down to investigate cause.
Aware it could be blocked air vent in the fill plug ( yet to check this ) .
Condition of engine unknown to me as I bought as a running roadworthy scooter last year.
Been wanting an excuse to have a nose inside and carry out a few mods along the way.