Lawn mower running rough

My briggs and Strattan mover was working fine up until I ran it dry using every drop of gas. The next time I used the mover it runs rough with RPM's going up and down but never stalling.
Is there a block in the carberator from the garbage at the bottom of the tank ? Do I have to take it apart and clean ?
Any help would be appreciated !!
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I'm not trying to be a smart ass but are you trying to run it on last years old fuel or have you got fresh gas in the tank. Last summer a couple of small engine mechanics I know where complaining about all the warrantee claims they where having that could be traced to bad fuel. Apparently all new lawn and garden equipment utilize new style carburetors that cut emissions but make the importance of fresh fuel a absolute must. The guys told me gas stored for as little as a month can cause problems.
Don't play around with the plug just put in a new one.
Good luck
Jimbo

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Yeah this could be a problem but I have used old fuel before and never had a problem. Maybe it has caught up with me.
Jimbo wrote:

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CanadianCowboy wrote:

Running it dry at the end of the season allows the diaphragm in the middle of the carburetor to dryout. The diaphragm gets hard and the accelerator pump can't function properly. The only cure is to buy a rebuilding kit (about $10), throw away all the jets and springs and slip in the diaphragm. It should take less than a half hour. This is what a "professional tune-up" consists of.
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Thank you very much !!!!!!!!!!!!!
William W. Plummer wrote:

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only cure? bah. just clean the carb. if that doesnt work then rebuild it.
randy
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I am confused. If you leave in old gas, then you can cause carberator problems. If you burn it off then you create carburetor problems (i.e. dried diaphragm) too.
So, what should you do at the end of the season before putting away the lawnmower?
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Use sta-bil or similar in your gas, leave it in the tank and use your mower hassle free.
My son has my 16 year old B & S classic and I'm not even sure that we have ever changed the spark plug. We do the oil once per year.
Colbyt
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On Sun, 24 Apr 2005 20:44:13 -0400, CanadianCowboy

Are you sure it isn't a dirty air cleaner. That will make the idle speed "hunt".
Ross
(To get email address ROT 13) ebff snipped-for-privacy@lnubb.pbz
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I have replaced all the basic necessities.
Air cleaner Spark plug Oil gas
RMD wrote:

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You might want to check all the carburetors control springs because if they are stretched or distorted that can cause serious idle and governor control problems. Over the years I have played around with making springs etc. but in the long run it's much easier to take the engine to a dealer so they can match up the proper spring for your model carburetor. Engine model number doesn't always designate the style or age of the carburetor.
Also a good idea to make sure all the carburetor and governor controls are moving freely and there are no restrictions causing air flow problems in the area around the governor assy.
Good luck
Jimbo .

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Thanks ....but keep in mind this happened AFTER I allowed my gas to run dry. Working great for 4 years prior to me running on a very low gas tank.
Jimbo wrote:

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CanadianCowboy wrote:

No amount of replacing and adjusting is going to fix the dried out diaphragm in the carburetor. Just buy a rebuild kit and spend the half hour!
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Had same problem last year. It was because I used old fuel. Was told fuel over a month old should be dumped in your auto tank. Use fresh gas in lawnmower. They are much more sensitive to fuel age. Cleaned carb and changed diaphram. Was pretty easy. Just pay attention to how parts are aligned as you remove them. A blocked gas cap can also cause the problem. There are vent holes on them.

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