If the bike will not idle but will run smooth after you rev it up then you have an air leak. Get the bike running and spray carb cleaner or something else at every visible gasket the bike has. Watch for it to change the motor speed (kill it, rev up). If that doesn't work then you should take the clutch and stator plate off and check the crank seals. Put soapy water where the crank goes into the case and roll the motor over. If the soap bubbles or gets sucked in then the seal is bad and needs to be replaced. Which sucks but has to be done if you are ever going to get it to idle. Good luck.