Filling oil on a dry sump bike like the XT6 or SRX6

I’ve seen a lot of questions relating to filling oil on dry sump engines like those in SRX6’s and XT6’s. In particular, the common issue is overfilling the oil. What happens is that at idle, dry sump engines often “wet sump”. The oil pump doesn’t produce quite enough pressure at idle to get all the oil to return to the oil tank, so it pools in the bottom of the engine cases. There is also a one way valve in the oil tank which prevents it from draining back into the sump. When the bike sits overnight some oil will most likely leak back down into the sump.

So if the oil is checked after the bike has stood for a while, the oil level may show as low due to drainage from the tank back down into the sump. Or, if the engine is started and let idle to circulate the oil, wet sumping means that the oil tank level may show as low.  Which then often leads to topping up the oil tank. Sound familiar? Sometimes this can be repeated multiple times leading to excessive overfilling (just ask me how I know this!). The excess oil then flows out the crankcase breather into the airbox.

So, when checking oil, I always do it straight after a ride if I can. After an oil change, I fill the the volume recommended in the service manual, then go for a ride, ensuring that I get the revs up and flick through the gears a bit. This way I know that the oil pump has been working and the oil tank level will indicative of the actual oil level.