I have an older WF thatt I am trying to get running again and it has developed an oil leak under the all the plastic and metal shrouds. My guess is it is the top of the head gasket. I havent torn the motor down yet, but I remember racing this back in the day and had some other racers with similar leaks…I just wanted to see if any one else had a similar situation or fix.
I also looked at the schematic and it could be the breather tube however it isnt dripping out of the existing breather tube but under the shroud.
A common problem is side cover bolts loosening up, you can check with a torque wrench but sometimes one or two will be just finger tight.
I would plan on going through the engine if possible, a new set of rings and a gasket kit will run about $50 if you can do the work yourself. If not, having a builder go through it will be money well spent if it keeps you from throwing a rod.