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Garden Tractors Discussion Forum

12 HP Craftman oil problem

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Robert E. Smith

07-17-2005 13:01:42




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Hey Guys Could someone tell me why my engine has started blowing oil out the crankcase vent tube into the carb ?
Mowed with it last weekend and it ran fine! started it up took off and it died! started it up again run for a second started smoking real bad and died! pulled carb off thinking something may be plugging it up and thats when I found it was full of oil! put carb back on after cleaning it out started ran fine then died again! pulled vent hose off carb started it up again runs great but oil is blowing out of vent tube!
What the heck happend? Bob

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Robert E. Smith

07-17-2005 19:10:20




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 Re: 12 HP Craftman oil problem in reply to Robert E. Smith, 07-17-2005 13:01:42  
Well if nothing else!
It got me motivated to dig into the Cub! (had to get the grass moved somehow)
Got the ole gal back up and running tonight and got the grass mowed! Had a bad condenser in the distributor! Don't see that very often!
Thanks everyone for you help and advice!
Now I just got something else to work on! it never ends dose it!



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tompepper

07-17-2005 18:18:43




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 Re: 12 HP Craftman oil problem in reply to Robert E. Smith, 07-17-2005 13:01:42  
Kents right.the newer B&S engines have a presurized system.and if its able to suck air in anywhere(dipstick)it will smoke like crazy.found that out on my 13.5.i forgot to tighten down the dip stick and started mowing.the pressure blew the dipstick out and it smoked worse than my wife does.....



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Dirty ED

07-17-2005 16:14:53




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 Re: 12 HP Craftman oil problem in reply to Robert E. Smith, 07-17-2005 13:01:42  
Is the oil level correct, or overfilled?
Check closely and smell the oil for an odor of gasoline, could be the carb seat is leaking and filling the crankcase. If this happens the oil will be thinned out enough to cause blowby around the rings pressurizing the crankcase and forcing oil into the carb.

Sounds like the initial run was burning the gasoline in the float bowl (therefore no smoke) but once the engine ran for a second or two it began forcing the gasoline contaminated oil into the carb, hence the now smoking condition.

But who knows what really happened, my expertise is new and used torpedoes.
DED

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Robert E. Smith

07-17-2005 16:22:04




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 Re: 12 HP Craftman oil problem in reply to Dirty ED, 07-17-2005 16:14:53  
Oil level is ok, that was one of the frist things I checked, wanted to see if carb had leacked fuel into crankcase but it was okeven a little low now.
Just don't understand what could have happend ?
It ran fine last week!
Thanks
Bob



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Kent of SW MO

07-17-2005 14:33:23




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 Re: 12 HP Craftman oil problem in reply to Robert E. Smith, 07-17-2005 13:01:42  
Oil blowing out the engine breather tube can be caused by one of two things. First is the oil fill tube/ dipstick fitting tight and sealing? If is is the only other thing is your piston rings have went south and you have serious blow-by. Sounds like it could be time for a rebuild.

Kent



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ldj

07-17-2005 17:43:02




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 Re: 12 HP Craftman oil problem in reply to Kent of SW MO, 07-17-2005 14:33:23  
Kent, How can the oil dip stick filler tube not having a good seal cause oil to blow out the breather tube?
L.D.



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ldj

07-18-2005 19:02:52




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 Re: 12 HP Craftman oil problem in reply to ldj, 07-17-2005 17:43:02  
Kent, I understand the negative pressure in the crankcase. However, if the seal around the dipstick is leaking, then there should be a lots of oil coming from there. He didn't say if there was or wasn't oil coming from there. If no oil is coming from there and that seal isn't good, then he isn't getting enough pressure in the crankcase to cause the big oil problem he has. To me this is a head scratcher and I'm scratching. Please clarify if I'm looking at it wrong.
L.D.

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Kent Of SW MO

07-18-2005 02:37:43




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 Re: 12 HP Craftman oil problem in reply to ldj, 07-17-2005 17:43:02  
The crankcase breather arraignment in most small 4-stroke engines is so designed to create a vacuum in the crankcase. If this vacuum is not maintained, everytime the piston comes down from top dead center, a pressure is created that goes out the breather valve arraignment which carries the oil mist with it.

Kent



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Robert E. Smith

07-17-2005 16:26:39




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 Re: 12 HP Craftman oil problem in reply to Kent of SW MO, 07-17-2005 14:33:23  
That was my thought also!
Was just hoping for something a little less costly if you know what I mean!
You know these things always happen at the worst times! My Cub Low Boy is down with a ignition problem right now!
Guess my grass is going to get a little out of hand till I can get things going again!
Thanks Bob



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Dannie

07-18-2005 03:45:40




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 Re: 12 HP Craftman oil problem in reply to Robert E. Smith, 07-17-2005 16:26:39  
Try a new breather and beather tube.



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