Check ? replace magneto on Cub 2165 16Hp Briggs

[Digger2013]

The left side cylinder is not firing so I suspect the mag may be bad. I read something about diodes in that circuit but I couldn't find anything tracing the wiring. Has anyone ever replaced a mag on this engine and can it be done without removing the engine ? Or better yet, is there anthing else I can check that would cause only the left cylinder from firing ?

 

[sox3]

Hi, Sorry your having a problem. The shut down wire that runs between the coils has a diode in it. Unplug the shut down wire from both coils and check for spark. If both have spark, bad diode in wiring. If no spark from coil, the coil is bad. You should always use a spark tester to check for spark.Try this and see what you get. Blower housing has to come off, you will have to see if its easier to remove engine or if you can just remove the cover. Ground wire part # is BS 844547.

 

[Digger2013]

Thanks for the info. Any idea where the diodes are located ? I have all the service manuals but unfortunately they don't cover the ignition system very well. I worked all day on removing the heat shield and I can see the mag but I don't see ant way around pullingthe whole engine which is a pain because I have to remove the drive shaft and exhaust !
Thanks for you advice, greatly appreciated. This is the first time I have ever joined a forum like this, hopefully I will be able to share some of my knowledge and experiences with others here as well.

 

[sox3]

The diodes are in the wiring harness that runs between the coils.

 

[Digger2013]

I assume that's under the flywheel shroud ? I'm trying to avoid tearing the whole thing apart if there's a posibility the problem is not the mag. I don't mind replacing the mag but want to avoid all that work if possible.

 

[sox3]

Like I said, you need to pull the grounding wire from the coils to see if it has spark. Most likely you will have to remove the shroud. If you can remove the wire without pulling the shroud, go for it. Long needle nose maybe?

 

[Digger2013]

OK, thanks again for the advice. I'll let you know how it turns out when I get it fixed.

 

[Digger2013]

I found the problem, actually it was a dirty air filter. The cylinder was firing, my spark tester was bad and I never thought to check it. The dirty air filter caused the plug to foul right away and not let the cylinder fire. It turned out to be a good learning experience for me and advise evryone to check the basics before tearing anything apart. One last note, the air filter was not obviously dirty, it was saturated with fuel so it looked clean !