Having problems starting the bike after it's been driven. In the mornings, it cranks right up cold no problems. But then when I ride it, it has problems starting back up if I shut it down and try to start it up after it's been sitting for awhile - but it's sporadic, doesn't happen every time - more often then not though lately. It will backfire, or It sounds like it just won't spark. If I leave it, and come back then about 45 minutes to an hour later, it will start right up. Driving me nuts.... any thoughts/suggestions? Battery is good and strong.