Troubleshooting fluid leakage onto the engine area?

Question

The bike is a Hero Honda Splendor Plus, and I've been seeing some fluid on the engine area for a month. Earlier I used to ignore it and wipe it off, but it returns. The bike's mileage has also reduced, which makes me concerned. I assume it would be some kind of oil leakage, because petrol would've evaporated immediately. Didn't see any obvious signs of tube cuts though. Pictures below.

Left side of the vehicle:

Right side of the vehicle (The engine oil dipstick is tightly lodged, so am sure it couldn't be the engine oil that's splashing out):

Right side view of tubes above:

I know I should show it to a mechanic, but before going there, I wanted to know what could be the probable causes and if it is something I could fix myself. Mechanics here have a habit of exaggerating the cause and overselling.

Answer 1

While this is an educated guess, I'd put money on the fact this is oil coming from the oil filler cap. It appears the cap isn't sealing completely, or possibly the cap isn't screwed on tight enough. If tightening it a little more doesn't work, you'll need to replace the seal on this to get it to stop. The seal itself may be an o-ring type, or it could be built in. If built in, you'll need to get a new cap.

Before replacing the cap, completely clean the area of the dirt cake which is starting to build. A clean engine is a happy engine. This will also help you ensure any effort you put into getting the slight oil leak to stop is successful. When you do clean the area, just use soap and water and a scrub brush. ENSURE the engine is completely cold when you do this. Putting water onto a hot engine can cause warpage and damage the engine.