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Inadvertent starting or backfire

Thoma's Avatar

Join Date: Dec 2007
Posts: 1

12-11-07, 09:31 AM   #1  
Inadvertent starting or backfire

Small gas engine manufacturers and others nearly always indicate that the spark plug wire be disconnected prior to inspecting, cleaning or turning the blade by hand. With newer mowers, you have a blade control handle which when released grounds out the ignition and applies an engine brake. Assuming the engine is hot (B&S 5hp.) my question is: Is it possible that turning the mower on it's side and turning the blade slightly by hand would cause it to start or perhaps backfire? The blade may have been turned backwards, backfired and caused the blade to turn suddenly even though it was said to have started.

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puey61's Avatar

Join Date: Apr 2004
Posts: 3,224

12-12-07, 02:25 AM   #2  
Is it possible...sure. Is it likely...no. For the ease of removing the spark plug wire from the spark plug why would you not? And save some precious fingers/appendages!!!

cheese's Avatar
Forum Topic Moderator

Join Date: Jul 2001
Posts: 16,564

12-13-07, 01:33 AM   #3  
If the kill switch is operating when the bar is released, then it won't fire. It's possible that something hindered proper operation of the switch, but that would probably still be evident by the switch still not working right. I don't think it could have fired while turning the blade backwards because the coil doesn't work in reverse rotation. I think the most likely scenario is that the blade was turned until the engine got just past the compression stroke, and then the compression forced the engine around the rest of the way. I doubt it ever fired.

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