A while back I picked up a Husqvarna 51 at a local thrift store for $35. Decent bar, like new chain, compression is 165 psi and what I thought was a good spark. It was partially disassembled, but for $35 I was going to take it home. For the life of me I couldn't get to run, sometimes it would fire if I put some fuel in the carburetor other times not. Looked as it if it had been stored for a long time with who knows what quality of fuel. I opted to replace the carburetor, rather than rebuilding the one on the saw. Tried starting it, with no joy to be had. Tried changing the carb settings to see if that helped...Nada.
Finally got the point that it wouldn't even pop. Time to check the spark again, nothing. Put the saw down for the evening and shopped for a new coil online. This morning, I pulled the kill switch lead off the coil and checked the spark. Bingo... or so I thought. With the kill switch wire still unplugged I installed the started cover, have it a little fuel down the throat and nothing. Pulled the spark plug again and checked for a spark, not even a weak one could be seen. Just before I was going to head inside to order a new coil, I grabbed an old fouled Champion RCY7Y that I had removed from a friends saw and checked the spark and a bright blue discharge was clearly evident. Grabbed a new NGK BPMR7A from my tool box and installed it, reconnected the kill switch lead and the saw roared to life. The spark plug that was in the saw when I "stole" it was a Bosch WS7F which looks to have a slightly shorted external insulator section as compared to the Champion and NGK plugs. It could have been that there was a gap between the spark plug boot contact and the spark plug which caused the ignition issue. Adjusted the carburetor setting with a tachometer and it purrs at 13,000 rpm on the rich side of the High setting.
Finally got the point that it wouldn't even pop. Time to check the spark again, nothing. Put the saw down for the evening and shopped for a new coil online. This morning, I pulled the kill switch lead off the coil and checked the spark. Bingo... or so I thought. With the kill switch wire still unplugged I installed the started cover, have it a little fuel down the throat and nothing. Pulled the spark plug again and checked for a spark, not even a weak one could be seen. Just before I was going to head inside to order a new coil, I grabbed an old fouled Champion RCY7Y that I had removed from a friends saw and checked the spark and a bright blue discharge was clearly evident. Grabbed a new NGK BPMR7A from my tool box and installed it, reconnected the kill switch lead and the saw roared to life. The spark plug that was in the saw when I "stole" it was a Bosch WS7F which looks to have a slightly shorted external insulator section as compared to the Champion and NGK plugs. It could have been that there was a gap between the spark plug boot contact and the spark plug which caused the ignition issue. Adjusted the carburetor setting with a tachometer and it purrs at 13,000 rpm on the rich side of the High setting.
