I would do a multiple stage cleanout. Do the motor flush like you have read, but instead of kerosene, I would just do a lightweight oil like a 0W-20 or something, but DO NOT RIDE IT. I would follow similar directions as with the kerosene. Change oil filters with a cheap fram or something, refill with 20W-50 then ride it lightly to clean it out and warm it up. Come back, change out oil and filter again, for the last time. Refill with Amsoil, Redline, or a good, quality oil, get a good filter, and go on down the road.
If at anytime you hear loud knocking, chances are you have a clogged oil passage and you have no oil pressure to a lifter. TURN IT OFF immediately, and let it sit for 5-10 minutes, try again. If the knocking persists, turn it off again, and it is time for a trip to the garage or shop because there is something in there it doesn't like, and likely won't work out.