B & S broke a push rod

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  #1  
Old 03-02-12, 06:27 PM
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B & S broke a push rod

I have a model 20A114-0363-E1 9.5 hp Briggs 7 Stratton engine in a snowblower.
It broke the exhaust push rod, and bent the intake rod. Why?

I replaced the rods and adjusted the valves, ( many times ) and it dont run right.

It sounds like its running on half choke. I shut it off after 5-10 seconds and the muffler is way to hot for that short of run, at times almost smoking hot.

What sould I do next?

Thanks, Buzz
 
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  #2  
Old 03-02-12, 10:18 PM
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Sounds like maybe a valve isn't closing all the way. You might have to remove the head and see what happened.
 
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Old 03-03-12, 05:07 AM
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I would check the height of the valve guides. Should not be more than 1/8" above the head casting.
IF a valve guide works up, the valve spring retainer will eventually hit it causing bent, broken push
rod which sometimes takes out the other push rod as well. B&S says no fix except new head, I have a fix at address below, put in proper format and remind me.

Walt Conner
 

Last edited by cheese; 03-03-12 at 07:03 AM.
  #4  
Old 03-03-12, 07:00 AM
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Just looking though the valve springs it appers that the exhaust guide is up. not sure though.

Also I see the valve seal on the intake has a spring built in on the top of it to help in the sealing, but dont see this on the exhaust side. Looking up the valve seals in parts site, they give one part number for valve seal. So does this mean intake and exhaust use same seal, or just one intake seal and no exhaust seal.
 
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Old 03-03-12, 07:00 AM
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Pretty good chance the guide has moved, as mentioned.

The exhaust valve doesn't have a seal... it gets too hot for a seal.
 
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Old 03-03-12, 07:03 AM
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I also removed pto side cover on engine all looks good in there. The lifters seem to look good, and all gears intacked, no missing teeth.
 
  #7  
Old 03-03-12, 07:12 AM
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What would cause the guide to move?

Is this a design problem?

Does this happen alot with these OHV Briggs engines?

There's not many hours on this engine. And I change the oil alot, at least three time a winter.
 
  #8  
Old 03-03-12, 07:39 AM
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Generally heat causes it. If the engine is running too lean (good chance of it with the lean carburetors they use to meet EPA requirements), and if it is working hard at less than full throttle, it can overheat the head enough to let the guides slip loose. Ethanol in the fuel seems to contribute to a lot of sticking valve problems, especially if the fuel gets old /stale. It's not a problem with Briggs really, it's what we get when the government gets involved. Lean carbs, bad fuel, more heat, less power per ounce of fuel (meaning less efficient/more pollution), more equipment / raw materials ruined and taking up space in the landfills. I guess you can tell I don't like ethanol fuel at all, lol.
 
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Old 03-03-12, 08:55 AM
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At the time they bent engine wasnt hot. Snowblower only moved about fifty feet, then went into about 2 feet deep shoveled snow bank and quit.

Maybe my gas mix killed it. 92 oct. gas with stabil added, and heet added.

What you think my gas?
 
  #10  
Old 03-03-12, 09:16 AM
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No expert...but isn't HEET basically either isopropanol or methanol (depending on the bottle color)? I would think that might have contributed to a hotter running condition.
 
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Old 03-03-12, 09:41 AM
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Red bottle heet...................
 
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Old 03-03-12, 10:04 AM
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According to what I can find...that's basically methanol. What the concentration is...I dunno.
 
  #13  
Old 03-03-12, 04:14 PM
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As said, heat usually is the problem. Plugged cooling shroud or cooling fins. Mouse nest in cooling shroud?

Valve Guide fix sent.

Walt Conner
 
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