Hello I have a 2006 Yamaha raptor 50 for my boy that I can’t get to run. Has spark when I test the plug against the block. Plug is wet so has fuel. Compression is good. This thing will not fire I get the odd backfire but it will not go. Any ideas would be greatly appreciated. Is it possible there is no spark under compression?

 

Are you sure, certain, positive, you have good compression. That engine is notorious for the valve clearances closing up and dropping the compression at cranking speeds. Set valve clearances anyway, it can't hurt. If they are correct and it still won't go, clean the carb out. An engine needs just the right fuel/air ratio to start, which is why some won't start without choke.