There are two things that may cause this that you cand check.. the first is an intake leak. I use a propane torch to check for leaks, less messy than WD40. Start the bike.. warn it up.. get it to idle.. now put the torch near the rubber intakes with it on.. if the engine "smooths out" .. you have found your problem. Next is dirt in the carb or filter.. also check the exhaust sytem for leaks.. stock jets today tend to make bikes run too lean in IMO and is done to keep the EPA happy with emissions and fuel consumption. Sometimes going one jet size larger will get rid of a cough. You will have to know how to read plugs to do this.. also your bike may have clips on the needle in the carb you can adjust the carb that way too.. usually there are 3 positions.. if you have a CV carb check to see the carb is working properly. A small leak in the rubber can only get worse. I do this by lifting the slide and then letting go.. it it drops quickly with no resistance.. there might be a problem.. it should have a little delay in dropping to operate right. Jim