Briggs- Oil and Smoke

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  #1  
Old 10-15-07, 06:42 PM
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Briggs- Oil and Smoke

A friend recently gave me a pretty old (1979 or so) Snapper HiVac mower with a 3.5 Briggs engine. It had apparently sat idle for a long time.

I've worked on Snappers before, so I was able to get this one running. In fact, it ran pretty well, with ample power and speed, except it seems to be burning almost as much oil as gas, especially after running about ten minutes. My impression was that the condition got worse as it ran.

I find it hard to believe an engine can run with power and apparently have decent compression, and yet burn so much oil (I literally had to add a quart after running it about 15 minutes).

Could this engine likely have a collapsed oil ring? Or, is it something else, such as a bad crankcase breather? The breather is a reed valve, I think, and pretty simple construction. I haven't found a bad one before, but I guess there is always a chance it is bad.

What are the more specific symptoms related to the probable causes or such major oil consumption in a small Briggs engine? Any simple fixes to rule out?

Is it worth re-ringing an old engine like this, as a winter project, or is it likely that the cylinder, crank, bearings, etc., are shot, and the whole engine ready for the scrap heap? There is no telling how long it may have run with this oil problem and with low crankcase oil at times.

I look forward to the reply of more knowledgeable folks than I am on this subject--

Matthew
 
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Old 10-15-07, 07:36 PM
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First, I'd suggest posting the engine's model and type numbers from the recoil shroud or flywheel. That way we know which engine we're dealing with. There are a ton of possibilities that could cause major oil consumption... bad breather, bad head gasket, bad valve guides, bad rings.. Post those numbers and go from there....
 
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Old 10-15-07, 07:57 PM
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QUOTE: My impression was that the condition got worse as it ran.

Check the oil.Smell of it.it sounds like the fuel inlet valve inside the carb is sticking open,this will make gas drain into the oil & make an engine smoke as well.
 
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Old 10-16-07, 12:20 AM
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Give the oil a check for gas smell, and for possible over-full level. If not, I'd suspect the oil ring is worn out or stuck. The head is easy to remove, pull it and have a look at the cylinder to give you an idea of the engine's condition internally.
 
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Old 10-16-07, 01:29 PM
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This is likely a diaphragm type carburetor since it is older AND a 3 1/2 horse, it will be highly unlikely that you have fuel migrating into the crankcase (oil) which would then point to worn piston rings as the cause of the heavy smoking.
 
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Old 10-16-07, 04:45 PM
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Thanks very much for your replies.

The engine is Model 110908, Type 0309 01, Code 79112004.
It has a pulsa-jet carb.

I'll pull the head and inspect. I know this is a hard question to answer, without more information, but in general, if the oil ring is shot, is it worth the effort to simply replace the rings and reassemble? As I mentioned, it seems to run fine other than the smoke and voluminous oil consumption.

Matthew
 
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Old 10-16-07, 05:02 PM
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As long as nothing else is bad, rings aren't a real expensive item so if you have the know-how to take it apart and put it back together, it'd be worth it in my opinion. According to Briggs' website, the standard ringset price is $20.50.
 
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Old 10-17-07, 07:51 AM
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I know it's easy to just drop in a new engine, and I may do that if I can find one cheap. However, I like crazy projects, so, I think I'll make it a winter project and probably invest more time than anyone in their right mind should...

I don't really need this mower, and I'm sure I'll give it away when I'm done fixing it, probably as a housewarming gift to some new homeowner friend.

Thanks, again. Appreciate your help and, if I tear the engine apart, I may return to this forum for some further guidance.

Matthew
 
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Old 10-17-07, 11:50 AM
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FYI, be sure to inspect AND measure the cylinder bore once apart. Even if it does not appear scored it may be well worn...beyond reasonable tolerances. If this is the case, you'd be further ahead finding a suitable replacement engine than boring this one.
 
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Old 10-18-07, 07:34 PM
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Thanks folks, much appreciated.

Matthew
 
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