About a month ago I tried to fire the Max up and it made a real loud popping noise through the carbs and it fouled the plugs. I changed the plugs and got it to fire up but I could hear the valves clattering. I took it to the dealer and had the carbs synched but the valves still clatter but it does not back fire through the carbs any more. It is a 06 and just turned 8k miles. Do you think the valves need adjusted? 
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