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B/S 7HP Motor - blows gas out of muffler - simples fixes nogo


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06-04-10, 06:55 PM   #1  
B/S 7HP Motor - blows gas out of muffler - simples fixes nogo

I have a Craftsman lawnmower, about 5 years old - it has a Briggs & Stratton 7hp motor.

Last week, it started running rough and ragged and blowing blue/white smoke (was hard to tell exactly) and finally died on me. After trying to start it, I noticed gas spitting out of the muffler.

Did some research, replaced needle/seat, cleaned everything out, drained the oil (had gas in it), put fresh in, got everything about the way it should be. Replaced the plug, confirmed I've got a spark, everything's back but the damn thing will still not turn over and start. It's still spitting gas out of the muffler.

At this point, I'm stumped and a bit worried that the engine has bigger problems. I'm mostly a garage mechanic, although breaking down engines doesn't scare me - did work on 350s and 4 cylinders for amateur stock cars but I'm not well equipped to do a complete engine overhaul. Anything else I can do or look at to confirm damage or something ruined or did I miss something in tuning up the carb?

Thanks.

Michael

 
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06-04-10, 08:54 PM   #2  
Post the engine #'s so the pros know what engine you have...This may sound silly,, but what does the air filter look like??? I see a lot of them plugged from tipping the machine, or just neglect & can cause lots of problems... Just a thought... Roger

 
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06-05-10, 08:32 AM   #3  
128602 0215 E1 020411 FA

The air filter was also soaked with gas and oil - I cleaned/blew it out. It's clean now and it still does the same thing.

 
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06-05-10, 08:43 AM   #4  
It's probably the float valve isn't seating. That's about the only place on a conventional bowl type carb that you can get that type of volume.

Take the little sucker apart and use a cuetip with some Comet or baking soda on it and rotate it back and forth in the float valve seat. Then clean it up and stick it back together.

It won't start until you get the flooding stopped and the gas blown out of the cylinder.

 
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06-05-10, 08:53 AM   #5  
Posted By: marbobj It's probably the float valve isn't seating. That's about the only place on a conventional bowl type carb that you can get that type of volume.

Take the little sucker apart and use a cuetip with some Comet or baking soda on it and rotate it back and forth in the float valve seat. Then clean it up and stick it back together.

It won't start until you get the flooding stopped and the gas blown out of the cylinder.
It's a brand new seat and needle - am I missing another area this could be happening?

 
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06-05-10, 09:00 AM   #6  
Posted By: ChicagoWiz 128602 0215 E1 020411 FA

The air filter was also soaked with gas and oil - I cleaned/blew it out. It's clean now and it still does the same thing.
Try it without the air filter. If it has been soaked with gas, it will never be the same.

 
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06-05-10, 09:30 AM   #7  
Posted By: BFHFixit Try it without the air filter. If it has been soaked with gas, it will never be the same.
No change. Still spits gas out of the muffler.

 
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06-05-10, 10:12 AM   #8  
Check to make sure the float valve is seating - new or not. If you have gas spitting out the muffler that would take a lot of full choking or a float valve not seating.

You could have something hanging up the float and preventing it from putting pressure on the valve or the float could be bad. With a light pressure on the float it should shutoff flow when the float is parallel to the carb casting.

The no start is definitely from the flooding.

 
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06-05-10, 10:18 AM   #9  
Well, an embarrassed update.

I've solved the spitting problem by removing the thoroughly soaked air filter AND putting the damn wire back on the plug. Kicked right over, spat out blue smoke for a few minutes and now is running same as always.

The original needle seat had been cracked and split, so I'm pretty sure the tuneup fixed the original problem. I just made a new problem with an idiot move. Now on to buy a new air filter and be done with this.

Thanks for the suggestions - you have no idea how happy I am I don't have to do valve or rings work on this guy.

 
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06-05-10, 10:22 AM   #10  
The pric e of being a DIYer is to often need to do a job over again two or three times until you figure out how to do it right.


DIYers usually aren't as efficient at doing stuff as experienced pros. That's one of the things to factor in when considering a DIY repair.


That's my experience, anyway.

 
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06-05-10, 10:23 AM   #11  
Hey, you're in good company!! The important thing is you got that little beast going again.

Tell your wife to go do the mowing now that you got HER mower fixed.

 
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06-05-10, 10:41 AM   #12  
@SeattlePioneer - too true. Although I have a funny story about a stock car and a ground strap...

@Marbobj - hehehe... I had to fix the drive belt/pulley first before she'd mow the yard. There was quite a bit of cussing on that job.

 
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