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Rough Idling


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10-10-03, 03:39 PM   #1  
Caper
Rough Idling

Hello, it looks like I came to the right place for advice on just about anything. This is bookmarked as I'm sure I'll be back I'm a real DIY'er guy. I just bought a 12 hp Craftsman Lawn Tractor. I think it was made in approx. 90. Model # is 944.607120. The problem is the idling is very rough, it is revving up and down. I put a new Champion plug in it RJ19LM, I changed the fuel filter, I checked the air filter seems ok, so I let it run with the filter off just to see if it was plugged but no difference. I put some Briggs and Stratton fuel additive in with the gas. I use this in my snowblower and 3 1/2 hp mower with great results. Any ideas would be greatly appreciated.


Last edited by Caper; 10-10-03 at 08:05 PM.
 
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10-10-03, 10:56 PM   #2  
Hello Caper!

Welcome to the small engines forum!

It sounds to me like you have carburetor problems. Adjustment may take care of the problem, or it may need cleaning/rebuilding. I don't know what make and model engine you have, but you can use the carb adjustments in this link as a reference for most older briggs and tecumseh engines: http://forum.doityourself.com/showth...hreadid=144840

Hope this helps!


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10-11-03, 03:31 AM   #3  
Caper
Cheese thanks for the reply, I'll definitely check out that link. It is a Briggs and Stratton engine. As the engine is idling you can see 2 parts on the carb moving back and forth as it idles up and down.

 
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10-11-03, 06:22 AM   #4  
Caper
Ok, I went through the motions of setting the carb and it is running about 80% better than when I got it and I have you to thank for that. I took the muffler off and blew it out with my compressor it wasn't too bad I did notice a bit of carbon inside the port where the muffler bolted to on the engine, I'm guessing it was probably caused from the way it had been running. I'm wondering if the spark or timing can be changed a little to smoothen it out a little more.


Last edited by Caper; 10-11-03 at 07:23 AM.
 
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10-11-03, 11:36 AM   #5  
There are no timing adjustments on this engine. You may need to clean the carburetor. If you post your engine model#, I'll know which carb you have and be able to give some more detail. Is it still surging? If you have a long tube type of carburetor, they are prone to surge when they get older, and it can be hard to stop the surging. The throttle shaft and bushings usually wear out and cause an air leak, which causes the surging. It could be something stopping up the carb too though. You could remove the bowl and look for water and rust in it.


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10-11-03, 03:42 PM   #6  
Caper
Cheese it is still surging a bit. The
model # 281 707
Type 0412 01
Code 90021231

 
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10-11-03, 11:43 PM   #7  
Does it have a teardrop shaped air filter with one hole for the mounting stud, or an oval shaped air filter with 2 holes? It has a flo-jet carb, but I'm not sure off the top of my head which one it is...the type of air filter will tell me. If you haven't replied by the time I get back here, I'll run the #s you gave me and find out which one you have.


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10-12-03, 09:21 AM   #8  
Caper
Cheese it's the oval shaped filter with 2 holes.

 
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10-12-03, 07:37 PM   #9  
Ok, remove the carb bowl and make sure it is clean and not rusty, If so, that may be the entire problem. If not, remove the brass screw recessed flush with the top of the carb. It is a long tube with small holes down the sides. Make sure the tube is clear, and all the holes are cleaned out.


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10-13-03, 08:55 AM   #10  
Caper
Cheese, there was a bit of rust in the bowl, I cleaned it up with a scotch pad. I removed the brass screw on top and just like you figured it was plugged up. It is running much smoother now. I am very thankful for your help.

 
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10-13-03, 09:50 PM   #11  
Anytime! Glad we could help you!


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