Toro Rider Backfires

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  #1  
Old 09-16-07, 07:10 PM
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Toro Rider Backfires

I have a Toro 30 inch rider with a 12 HP briggs engine. It started to lose some power and run rough and then after a little while it started to backfire a flame out the exhaust.
I am thinking that could be a bad valve, waddyathink?????
 
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Old 09-17-07, 10:44 PM
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Sounds to me like something got into the carb (water, rust?) and started restricting the fuel. The backfiring like that is an indication of lean conditions.
 
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Old 09-18-07, 07:59 AM
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The Carb

I never thought that a carb could make a motor backfire like that. If it is lean where does it get the fuel to shoot a large flame out the exhaust with a sound like a pistol shot.
How do I check it??
 
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Old 09-18-07, 11:50 PM
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A lean engine backfires because of increased combustion temperatures. The richer the engine is, the cooler the combustion chamber is. When it gets too lean, the combustion chamber and the muffler get so hot that when the fuel enters the cylinder it contacts the hot surfaces and ignites prematurely while the exhaust valve is still closing. (there is a time during engine operation where both valves are open...just as the engine begins to take in the fuel mixture). It's a well known fact that a lean engine pops and backfires.

Another possibility is a loose valve seat or bad valve as you suspect, but since it requires more effort to check, and is less likely than the fuel possibility, I suggested checking the fuel flow first. Without seeing and hearing it, that's my best guess given the info we have.
 
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Old 09-19-07, 06:27 AM
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Won't start now

This morning it will not start so I pulled the plug, it was sooty black and a little wet, I may have flooded it some, I did a compression check and all I can get is almost 60 PSI
The plug is almost against the transmission and very hard to reach
What now??
 
  #6  
Old 09-19-07, 06:53 AM
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Things that make you say Damn

Cleaned and regapped the plug and put it back it and turned the key, it fired right off, ran a few seconds and quit.

Pulled and rechecked the plug and thought I saw the gap was closed, I reached for a rag and then the gap was back, Thought my eyes went bad. As I moved my arm I heard a click from the plug in my hand. The porcelean insulator was loose and sliding back and forth on the center electrode.

What would make it break like that?

Anyway I grabbed a used plug I had saved from my outboard that was the same overall length but a center fire job by NGK, screwed it in and it fired right off. Gonna go buy a proper plug now, still runs rough at at idle though.

Any one know what the compression is supposed to be?
 
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Old 09-19-07, 07:42 AM
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60 seems a bit low to me which might lead some thought about the valve problem. Did you inspect the fuel system as cheese indicated? Does it have a choke so that you could 'richen' the fuel/air mixture and see if it smoothes out?The backfiring can be pretty violent which I think would damage your spark plug. There are my $.01 for the moment.
 
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Old 09-19-07, 11:23 AM
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Tuned it up

My compression gauge leaks down rapidly so it might be reading low
I put in a new Plug, cleaned the air filter and changed the oil, started it up and drove it around to get it warmed up and adjusted the carb and now it runs smooth again.

I never would have thought a bad plug would cause all that havoc. reminds me of my high school days., we would run my mothers car past the school in second gear, cut the ignition, wait a few seconds and turn the key back on and, Boom, huge blast, was a lot of fun until I blew the bottom of the muffler out. same thing was happeneing here, the muffler was loading up with gas until the plug fired, then BOOM. This Toro has a big muffler on it.
Thanks for the advice
 
  #9  
Old 09-19-07, 07:48 PM
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Well that was a simple fix! If it was doing that, it was backfiring louder than what I was thinking. I see you referenced a pistol shot, but that didn't really sink in. Lean mixture causes more "popping" but not big BOOMs, lol!

Glad it was an easy fix!
 
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