Small Engines (Lawn Mowers, etc.): Non-start ride on mower, typical measurements, eager anticipation

Question
Hi John. I have a 18.8 hp B&S on MTD my ride on mower. The other day, the mower failed to start. There is plenty of fresh fuel and the plugs are new. I pulled a plug and tested the spark to exhaust manifold, under crank and found that it looked quite weak and was white/pale blue in colour. Investigating further, I pulled the top off and measured the restance of the magneto coil between both ends of the winding. It measured 0.1 to 0.2 Ohm. I believe this to be the primary winding and would expect this to have been higher. I measured between the plug leads and primary winding. This measured >20 M Ohm. My questions of you are, 1. What should be the colour of the spark and how strong should it be, 2. Because there appears to be no connectivity between each spark plug lead, is there some sort of capacitive coupling between them and 3, Does the low impedance of the winding indicate that there are shorted turns? If not, can you please indicate what typical measurements should be between points? I am also told that this part is likely to cost me in the vacinity of AUD 150 to purchase, something I am wishing to avoid if possible. I thank you, in eager anticipation.

Answer
 Hello Colin:

 The Newer Coils with the Built in Ignition Module will either have fire or not. When the Plug isnt in the Cylinder and under Pressure the Spark will Look Weak. Check the Carb. It Sounds like the Carb Needs to be Cleaned and Overhauled. Be sure the Ports and Passages are Blown out with Compressed Air. Dont Worry about the Coil. White to Pale Blue is Actually a Hot Spark. A Yellow Color Spark is Considered Weak. Spray a Small Amount of Gas into the Carb Throat. Start the Mower. If it Runs and Quits then the Carb is the Problem. Hope this Helps.

 Good Luck


 Respectfully

 John