I recently bought a 1979 Honda XR500, it runs great and fine but after riding the bike for a minute and then proceeding to pull the clutch in to come to a stop the engine begins to rev up and the only way I can get the bike to stop is by killing it. It idles perfect when it’s first kicked over but as free riding it for a second it will rev up when you pull the clutch in. I’m not giving it gas either it’s a reving up by itself. Any help? Thanks