TOPIC:

Just pulled my filters off to clean them. Each carb had a small amount of oil on the lip and in the filter? Never seen this before. It got ran pretty hard last weekend, would that have something to do with it?  Any ideas?  Thanks 

Could the filters have been over oiled when they were last installed?

It's probably evaporated fuel if you used ethanol laced fuel. The residue from evaporated ethanol fuel is brown. When fully evaporated its looks like a varnish, this is what clogs carbs if bikes are left for a while without draining the carbs.
There's no engine fluids that get to carbs other than fuel. 

Yes, but not that much. And this was like engine oil. 

Thanks warren.  That could be it. Just seemed excessive I got fuel at 3 different stations last weekend though. 

Is it fair to assume that you are running pods and the crankcase is venting to atmosphere ?

Into filter

When you "into filter" is this a separate unit or the air filter (normally if the breather is connected to the air filter oil in the intake is a sign of excessive crankcase pressure)

Sorry yes I have pods and a separate filter/breather on the case. 

There aren't too many options for oil to get into the intake under these circumstances, a leaking valve seal would normally result in the oil being drawn in and burnt. it would be very unusual for oil to find it's way out to the carb intakes ???

Thanks. That’s what I thought. Like Warren said. Prob a fuel issue. Just never noticed it before

You may be dealing with intake reversion and leaky valve seals.

www.motortrend.com/how-to/ctrp-1008-intake-reversion/

Your exhaust pipe may be sending a strong positive pressure wave back to the cylinder during overlap at certain rpm's.
This is due to pipe length and internal size changes of the primary pipe.
Collector design and placement plays a role as well.
Two stroke tuners have been use this tuning method to their advantage.
You can use it as well but you need to do the math.

The cloud of fuel above the intake trumpets shows reversion in action on the Renault F1 engine.



 

Are the valves adjusted properly?  If the intake valves are hanging open, there may be a bit more blow back.