Winkster 12 #1 Posted November 16, 2023 I'm exasperated. I've tried the new spark plug. BPR7HS. Bought better gas (93 octance. Wrong?) Adjusted carb 2 1/2 Idle fuel, 2 main fuel. Started after some starter fluid but LOTS of backfire. I only need the thing to run (1977 K21 12 hp) so I don't have to rake. Cutting season is over. I'm lazy. Won't start now but kinda worn out from hopping on and off the darn thing. Ideas? It did quit a month ago and I replaced the spark plug and condenser. Backfired then so stupidly I tried adjusting the carb. Should I do points too? Winkster Share this post Link to post Share on other sites
gwest_ca-(File Mod) 10,504 #2 Posted November 16, 2023 Battery ignition with points and condenser? Remove the spark plug so the engine can be turned over by hand. Check the voltage with a meter or test lamp at the coil (+) - should be battery voltage. Check the voltage at the coil (-) terminal while rotating the flywheel. When the points are closed you should have 0 volts. When the points are open you should have battery voltage. This change in voltage should occur once for every two rotations of the flywheel. It is the change in voltage that fires the plug. If you do not get the 0 volts the points are not closing or are oxidized so no electrical contact when closed. Clean and check point gap .018" 2 Share this post Link to post Share on other sites
