I do not think I have this problem, like Hellsoldier said he was having. I was just wondering if you can tell by how the bike runs if one is not firing. Since we have two, would it be noticeable it one did stop working. The gas mixture would still ignite. Has anyone been able to tell that one plug is not working, or do you have to physically check for a spark at each plug to tell. Any thoughts on this would be appreciated.