Small Engines (Lawn Mowers, etc.)/Ryobi with weak spark



I have a (until now) very reliable Ryobi Brushcutter RBC30SBSNB that has stopped working suddenly while in use. There was no surging or changes in revs to indicate a possible fuel problem. After replacing the spark plug which had a light brown burn colour to the centre electrode porcelain, I still had no spark. I purchased a new ignition module and fitted that using a business card to set the gap. I now have a very weak and intermittent spark, even with the kill switch wire disconnected. I would appreciate any help/advice you can offer. Regards,  Allen

ANSWER: Did you order the ignition module from Ryobi?  Are there any markings on the ignition module such as "This side out" or "Flywheel side"?


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QUESTION: Yes the module was ordered from a Ryobi stockist (Bunnings in Australia) from the relevant parts list and diagram. The module cannot be reversed when fitting. Part No.308389004

The color of the spark rarely makes a difference.  How do you know the spark is weak?  An inline spark test similar to the one Briggs sells with a .166 inch gap works well to determine if the spark is weak.  I have only seen one coil with weak spark.  The coil would produce spark across a spark plug and shock you but it would not jump the .166 inch air gap of the inline ignition module.

Did you replace the spark plug?  Did you check the engine compression?


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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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