I was out riding the other day on some trails.1st-3rd gear mostly. We came to a road portion of the ride and we hit some high speeds, wide open fifth gear for a bit. While on the road I noticed what sounded sort of like a pinging, but only in the lower end of the throttle range in the high gear. It wasn't an overbearing ping, but was definitely there. When I opened the throttle up, the noise either dissipated, or was muffled out by the increased "braaap". Anyone else experience this? I am normally in the woods and don't open it up like that, so am not sure if this is normal, or precursor to disaster.