Briggs and Stratton 17.5 hp, white smoke

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  #1  
Old 11-27-06, 07:28 AM
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Briggs and Stratton 17.5 hp, white smoke

I have a 2 year old Troy-Bilt lawn tractor with a B&S 17.5 HP OHV engine (31c707, type 0154) that yesterday started blowing out white smoke (significant smoking, not just a few puffs). The engine would slow to the point of almost stalling, and then recover and blow out the white smoke. It continued smoking to a lesser degree when the engine was running strong, but the cycle repeated about every 30 sec and finally the engine cut out. I was able to restart it, but the pattern continued.

From what I've read, it could be internal (rings) or external (crankcase breather?) blocked. Any suggestions on troubleshooting this? The engine is only 2 years old and not heavily used (about 50-75 hours on the engine total). Oil and air filters changed about 2 months ago, no problems with the engine before this.

Thanks,
Greg
 
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  #2  
Old 11-27-06, 07:46 AM
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First check the oil level in your crankcase. It could have been contaminated with fuel through the carburetor and raised the level, or if any oil was added it could simply be overfull.

If that all checks out alright, I would suspect a blown cylinder head gasket. A blown cylinder head gasket on an overhead valve engine will sometimes leak in the area around the valve push rods. This will allow combustion back into the crankcase and force oil past the rings and through the breather.
 

Last edited by 30yearTech; 11-27-06 at 01:31 PM.
  #3  
Old 11-27-06, 01:19 PM
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It sound like (as first mentioned) it may have been overfilled. If not check for oil leaks. If equipped ,is the oil fiter loose or leaking? Was the oil drain replaced properly? Is it loose or leaking? Check the spark plugs to see if oil deposit are built-up.
 
  #4  
Old 11-27-06, 06:14 PM
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checked the oil level when I got home tonight and it was a little high, and smelled like gas. I'm pretty sure that it wasn't overfilled before because I am pretty careful with things like that. It has been doing fine in the last couple of months since I changed the oil. This was a pretty sudden change - the last time I used it, it ran fine about 3-4 weeks ago.

My manual lists that the breather may be bad as a possibility for smoking, anyway to differentiate the blown head gasket from that? Or is the gas smell on the dipstick a clear indicator?

How hard is the repair? I have the B&S service manual on the way. I rebuilt (carb, points, ignition) a 4 HP Tecumseh engine last year for a snowblower, so I have a little experience with small engines, but I haven't worked on something this size yet.

Thanks for helping,
Greg
 
  #5  
Old 11-27-06, 07:05 PM
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The carburetor may be flooding and gas entering the oil, if the oil smells like gas thats a pretty good indicator that there may be a problem with your carburetor.

Drain the oil and refill with fresh oil, then run the unit. I would remove the air filter as it may also become contaminated with oil if oil is blowing past the breather. Let it run at a fast idle for several minutes to see if the oil smoke clears up. Breathers can cause this problem, but I rarely ever see one fail, in fact I see the head gaskets fail more often then the breather.

If the oil clears up and it runs alright, then check to see if the carburetor is flooding.
 
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