Welcome to the forum. As Flash pointed out, what you are finding at the oil filler is normal.
Need some more details about this shaking. Is the shaking continuous, increasing and decreasing with RPM's? At a stop, being ridden, or both?
I'm sure you more than concerned about all this, and wild speculation on my part based on scant details won't help much. Get us some more details. I'd also suggest adding your location to your user profile. You'd be surprised where help can come from if they know where you are....
Your engine has a chain driven counter balancer system to minimize engine vibration. It has a history of issues ranging from components of the system breaking and getting lost, to these broken parts causing catastrophic engine failure. I don't want to be an alarmist, and any reference to the balancer system would be speculation at this point. It could as easily be a missing motor mount bolt.
“many a trip continues long after movement in time and space have ceased”- Steinbeck, [I]"Travels with Charlie"
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