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B&S 21hp mower often adjust choke to run


davefrommd's Avatar
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Join Date: Jul 2004
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08-21-05, 05:52 PM   #1  
B&S 21hp mower often adjust choke to run

I have a 21hp B&S lawntractor I think it's a murry. The air filter had become loose one day I discovered. It was dirty so I bought a new airfilter/prefilter. It's possible some dust & contaminents could have gotten into the carburetor. Carburetor has no lean/rich screws. The engine normally starts with the choke on full. After it starts I push the choke in to about 1/2. It doesn't want to run with the choke off. It only seems to run with the choke on 1/2 to 3/4. As I run the mower every once in a while I have to readjust the choke as it begins to stall and sputter. I drained and cleaned the gas tank. Sometimes if I hit a rough spot on the lawn then I have to adjust the choke again. Sure wish I knew what was causing the problem. I changed the sparkplugs and oil. Any help or suggestions would be greatly appreciated. Thanks in advance. dave

 
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cheese's Avatar
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08-21-05, 10:39 PM   #2  
Hello Dave,

You need to disassemble and clean the carburetor.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
firepaw's Avatar
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08-22-05, 01:27 PM   #3  
Dave,
Here's something to try before you go and open up your carb. Check the bolts that attach the carb to the manifold. I had troubles with two this season. They seemed to want more choke than usual to start, and once warmed up a bit, the choke had to be "fiddled with". Noticed the loose mounting bolts AFTER pulling the top off of the first carb. Dang. The bolts were loose on the second one too. Tightening them cured the problem.

 
cheese's Avatar
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08-23-05, 12:58 AM   #4  
Thanks for the thought Firepaw....I haven't run into that yet, but now I'll look for that next time before going into the carb, just in case.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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08-23-05, 02:34 PM   #5  
In such a case as firepaw described, I'd replace the mounting gasket automatically. With the carburetor vibrating from being loose, it is quite likely that it will damage the gasket and still give a lean condition even after the bolts are tightened.

 
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08-24-05, 04:45 PM   #6  
Thanks!!

Hey thanks for the good help. I'll check those bolts. Never thought of checking for loose bolts. It might be a few days before I get to it but I will let you know what I find. Thanks again for all the good help. Are these carburetors easy to rebuild. I've rebuilt chainsaw and 2 cycle snowthrower carbs before but never this kind of carb. dave

 
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