This is a Suzuki Djebel 250 that a good riding buddy gave me. My friend rides like a looney and couldn't control himself riding on boulders pretending that this off-roader is a Trials bike. He rode over a boulder and hit the engine hard and cracked the engine. I was looking for a donor engine but I wanted to take it for a spin before the repairs. The oil leak was bad but it didn't stop me from riding it.
To stop the oil from leaking, first I drained the engine oil, drained the fuel, flipped the bike on it's back, cleaned the engine with a wire brush and parts cleaner spray and applied liquid engine gasket and waited for a week. After a week I rode the bike off-road and had a good time.
This is just a quick fix and I recommend to do proper repairs. For crazy off-road riders, I suggest you to bring a tube of engine gasket sealant in your tool pouch. Based on my experience, twice I did this quick fix up in the mountain creek when my riding buddy crashed his Trials bike on a boulder cracking his bike's clutch case cover. Pushing the bike was not an option because we were about 7 kilometers away from our vans and there were no roads because we were on top of a creek. We still have to cover lots of grounds, ride very steep climbs and jump lots of boulders and that will be impossible without the engine working. I flipped the bike on it's side and got some leaves to clean the dripping oil from the clutch case cover, applied engine gasket sealer and waited for about an hour, started the bike and my friend rode his bike back to safety. The next week my friend came to ride again but still didn't replace the clutch cover. It took him about 3 months to replace his clutch cover and kept riding his patched-up bike. He always told us that "if it ain't leaking, I ain't fixing"... crazy guy, hahaha!