Small Engines (Lawn Mowers, etc.): No spark on my Yamaha lawn mower, yamaha ylm, lawn mower parts

Question
I have a Yahama YLM 342 SR rotary lawn mower which recently just cut out without warning. I have established that there is no spark at the plug.

I've had a look under the outer plastic cover and all I can see to go wrong is a coil device which is fitted to a a layered metal former which seems to take timing impulses from inserts set into the alloy flywheel. The spark plug lead comes off this coil unit along with one other thin wire which I think may be for the engine cut off circuit. The wiring for the cut off swith seems to be in excellent condition.

What I really need to know is do these coil type devices  fail and is this likely to be the cause of my problem or are there further electric components below the flywheel cover which could have failed?

The mower is a Yamaha YLM 342 SR, Its self-propelled and is 112 cc. The serial number is JK7 / 100121. I can't even find a stockist of Yamaha lawn mower parts in the UK where I live, so I would really appreciate your advice!

Phil

Answer
Hello Phil:

Remove the Spark Plug. Wrap a Wire Around the Threads and Attach the Other End of the Wire to the Engine Block Turn the Engine and See if the Plug Fires. If No, then Disconnect the Shut Off Wire  at the Control Bracket First, Check for Fire at the Plug. If Still No Fire at the Plug; Then Disconnect the Shut Off Wire at the Coil (usually requires removal of the blower housing) and Check for Fire at the Plug. If No Fire at the Plug , then the Coil/Ign Module is Bad. The Coil/Ign Module to Flywheel Gap is .020in. On Some Model JD Engines, there is a Igniter that Goes Bad and Not the Coil. The Igniter is the Same as an Ignition Module. If the Plug Fires at Anytime During these 2 Checks, then a Safety Switch or Wire May be the Problem. Yes the Engine will Turn Even with a Bad Safety Switch. The Blade Safety is Usually the Cause of this. The Starter Turns and The Engine Doesn't Fire is an Indication of a Bad Coil/Ign Module or a Faulty Blade Safety Switch. The Clutch Safety Prevents the Starter from Engaging so the Mower Does Not Move when the Starter Turns the Engine. The Seat Safety is Designed to Stop the Engine if the Blades are Engaged or the Clutch Safety is Not Engaged when you Leave the Seat. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John