Posts: 3508
Location: Elk River, Minnesota | Hiya,
something to check...
take the plugs out of the head but plug the bottom one into the spark plug wire. Set the other end of the plug in a place that can touch the block, then turn the motor over....see how much spark there is with multiple plugs. Then, check the other two cylinders and see if there is more or less spark using the same order of the plugs used to test the bottom. If there is more spark from all plugs, then change the coil from that bottom cylinder to a middle cylinder and re-test. If the low spark continues, you can narrow it down to that particular coil.
The next thing you can do is quickly do a compression check on the cylinders (if you have access to a tester...they aren't too expensive and nice to have when diagnosing a problem). Get the engine warm and then pull all plugs. Test each cylinder for compression. If that bottom cylinder does not hold, or is significantly lower in compression, it will show up here...
The other thing I would be wondering about is if you have a carb that just needs a good cleaning too. If a diaphram sticks closed or open here and there, it will show on the plug as well....
Couple of things to try out at home to help... Save you the shop money too.
Steve
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