What oil were you using? I know everyone gonna hate but why you running 50:1 on that motor if your not competitive drag. 32:1 and they're happy for a long time.you also have to be careful with oils at this time of year some separate in temps below 40* , it's best to call the number on the bottle and pick there brain, if they don't know don't run it. I've had two bikes within the last month squeak top ends from oil separation . Both engines held pressure tests before tear down so after some testing and fuel tests that was the only explanation unless both these guys flat out put no oil in