Welcome to the site !!
Did your friend ride it at the same elevations you do ?? , it could be that its jetted for a different altitude , or the Pilot Jet has clogged due to sitting with fuel in the carb , either of which are easy fixes , when starting it after falling are you using the Hot Start Lever and
NO throttle ?? , this would be the starting procedure for a bike that has been warmed up and has stalled or laid on its side and ended up rich from the fuel pouring down the intake tract , if you touch the throttle even while using the Hot Start , it will still struggle to start because using the throttle changes the mixture that the Hot Start is trying to achieve to get a flooded bike to start
Also , VERY IMPORTANT , when starting a stalled/tipped over bike , it must ALWAYS be in Neutral , trying to start it in gear will usually end up in frustration and a sore leg , the drag from the clutch will slow the engine enough that it will be all but impossible to start while in gear
A little more info like elevation your riding , and where your friend rode it (elevation) would help , what jets are in it ?? (Pilot and Main) and if it did sit for more than 1 month with gas in it would be nice to know , these are all factors that could lead to your issue
The Octane should be fine , they run here on 91 , does your fuel contain Ethanol ?? , and does it pop thru the muffler when you let off the throttle when riding ?? (not on the stand , but under a load when riding) , this would be a indication of a lean condition , has the plug been checked/replaced recently ??
When its cold(the bike itself) how does it start ??
It sounds like it could either be jetting is off , or a clogged jet (depending on exact symptoms) , but a little more info is needed , you also might want to post in the Jetting section of the forum , as we have a resident Carb Guru that knows more about diagnosing carb issues than anyone (
leardriver) , you might try to PM him , but if anyone can figure out your issue , its him , and having the answers to the questions i asked will help him diagnose as well