Re: lose spark on my john 6 hp......why??
Rcobb.... If it's an actual backfire, a loud explosion out the exhaust that wants to yank the starter cord out of your hand, you have the s/plug wires reversed.<br /><br />If it's a mild backfire, sort of spitting out the carburetor throat, the carburetor is fouled and should be cleaned. After cleaning (be sure to clean the high speed jet in the bottom center of the float chamber), the proper method to adjust it is as follows:<br /><br />Carburetor Adjustment - Single S/S Adjustable Needle Valve)<br /><br />Initial setting is: Slow speed (top) = seat gently, then open 1-1/2 turns.<br /><br />Start the engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting. <br /><br />When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
