With 1,900 miles the rings are probably well seated if a conventional petroleum oil was used. Thus a switch to a full synthetic now might give you easier shifting and better mileage. Topping the list of recommended oils by our members seems to be the Mobil 1 4T in a 20w50. The 4T designation implies compatibility in a wet clutch 4 stroke motorcycle engine and is not exclusive to the Mobile brand. For example I just purchased the Castrol equivalent full synthetic four stroke motorcycle oil.
Possible downside of more slippery full synthetic is sometimes cylinder base gaskets start weeping a bit of oil. However base gasket is fairly easy to replace and a little maintenance for a 1988 motorcycle is to be expected.
One quart bottle for ~$9 should make your bike happy. You hopefully have the infinitely re-usable mesh oil filter in the cylinder head so that could be simply cleaned and reinstalled. Do not confuse this with the second wire mesh filter @ bottom of engine where you drain out the old oil...both need cleaning. I just use hot water and detergent in the laundry sink and hope the wife doesn't catch me.