I have been fixing bikes for years but this one has me stumped. old Big Bear with slight miss or stumble only during hard acceleration. I have jetting tons of carbs and this one really seems like "spark snuffing". I have moved the needle and changed the main and just cannot get the carb to give me a direction to go.

Seems to get worse with heat, idles fine, starts fine. I pulled the plug when engine was hot and looked pretty wimpy. Could not hear the "snap" I should and was a small but blue spark.

Mag tested good and making proper voltages, primary side of Ign coil is in spec, but secondary should be 10-15K and showing 6.9K ohms. I have never seen a coil act like this and still not confident that is it. Usually they work or they don't unless dealing with the integrated coil packs of the modern.

Anyone seen this? Do I have a suspect? Usually if I have a bad coil, it is either VERY low or VERY high resistance. IE, obviously bad or suspect.

 

Electrical components can do weird things, but 6900 ohms is WAY out of spec. Electrical stuff can usually work correctly +/- 10% of spec, so the most you should see on your coil is 9000-16500 ohms. A coil is only around $30 so at least it's the cheapest electrical part to go bad. Usually a coil that is bad with very high or low readings probably don't work at all, right? This one is not the usual, it still halfway works.