A few things to try are to locate and clean air filter if it is a foam material then itcan be gently cleaned with a rew drops of dawn dish soap.and warm water. Pat dry and gently blow out with compressed air if possible.Let dry thourghly before reinstallation.I have used dawn soap for years because it does a good jod of dissolving grease. If filter is a fiber type or if foam is badly torn then it needs replaced.
Remove cover from exhaust and remove spark arrestor. If it has much carbon build up on it then you can clean with spray carb and chock cleaner.Blow out excess wiyh compressed air and brush any remaining particles of carbon with a fine steel brush let dry and reinstall. Check plug for proper gap and condition of electrode. If it has much cabon build up then try to scrape clean and reset plug gap.Check porcelin insulation to make sure there are no hairline fractures in it. If in doubt then replace your plug. Also check gas tank cap to make sure that the vent holes is open.I hope some of this helps you. Thank you very much.