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lawn mower low rpm


ctmal's Avatar
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04-07-04, 03:51 PM   #1  
lawn mower low rpm

I have a Murray lawnmower with a Briggs and Stratton engine.
Starting at the end of last season(of course I put it off until now), the engine sounds like it is not running at the full rpm it used to. I'm looking for some ideas on what to check before taking it in for service.

It has oil, fresh gas, and the air cleaner looks clean. The spark plug looks a little dirty, but I'm not sure this would cause it to slow down.

Thanks for your help,
Chris

 
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04-07-04, 04:36 PM   #2  
Hi: Chris

Air filter may look clean but be imbedded with dirt. In that fashion restricting air flow and the engine runs slowly or poorly. Intent is to find the simplest of solutions before assuming any bigger problems exist.

Simple test. Start and run engine with air filter out. If engine runs fine, filter is the problem. Before testing, remove filter and clean area around carb.

Thought I would toss that clean first disclaimer in b4 my peers dam near have heart failure...haha. Few mintues of running without an air filter will not distroy or harm the engine.

Engine may have fuel flow restrictions and or carb problems. Lets start with the smallest possible causes first. Use the reply button to update how the no filter test resulted.

Regards & Good Luck. Sharp Advice.
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04-07-04, 04:37 PM   #3  
Usually the main thing that makes a engine either not run right or not at all is the carberator. The first thing anyone should do every year is clean it. You should take your carb apart and clean it theroughly. Keep in mind that there are many areas inside of a carb that can be dirty, especailly the holes in the screws which you will see and on the main jet. Got to get that all clean. Once done reinstall and it should be running again. Don't forget to set your mixture properly aftor your done. The rule is, tighten till seated than back it off 1/2 turn.

PS: Use Automotive GumOut spray and a soft brush and or soft rag to clean the carb.

 
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04-07-04, 06:28 PM   #4  
low RPM

The first thing I would check is your linkage. I had mine do this a while back and it turned out the linkage had gotten battery acid on it and was not working properly. Just my two cents.

 
ctmal's Avatar
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04-08-04, 02:21 PM   #5  
I tried the filter test, it didn't make a difference. I also looked around for any noticable linkage problems, but there didn't seem to be any. I also sprayed carb cleaner in the carb but that didn't help. Is the next step removing the carb?

 
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04-08-04, 02:34 PM   #6  
Hi Chris

One more thing to test. Pull off the fuel line from the carb. The fuel should flow out fully and continuously. If not fully, indicates a fuel restriction some where. May be a filter inside the tank or a restricted fuel line, etc.

If the fuel slows down or stops, the air vent opening in the fuel tanks cap is restricted and or blocked or plugged. If fuel slows down and or stops, remove fuel tank gas cap and notice the change in fuel flow.

Once cap is removed the fuel will resume full flow. Indicates the cap vent is restricted. A restricted fuel flow into carb will also cause the engine problem described.

That is the last test prior to carb cleaning. Cleaning carb would not solve the current problem, >>>>if the vent hole in the fuel cap where still restricted or plugged up.<<<<

****Carb may be clean but without the full supply of fuel cause by the fuel cap would solve nothing.****

In my opinion, carb cleaning is only required if there is infact a carb problem, not done yearly or not done unless all other possible causes are infact not the cause of any engine running problems. Carb cleaning is a last resort issue after all other possible causes are eliminated.

Lets not assume or jump off the deep end until we are sure we can swim and know the depth of the water.

Regards & Good Luck. Sharp Advice.
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04-08-04, 03:00 PM   #7  
My too cents!

You didn't mention if you had a walk-behind or a riding mower. It sounds to me as though you have a walk-behind. Tell me. Do you have shrubbery that you mow under? If so, you likely could have tweeked the governor spring arm. This is the arm at which point the gov. spring attaches on the speed control end (right end as viewed from the carburetor side). This arm can be "adjusted." If in fact this is your trouble, using your finger, pull on the arm, thereby creating more spring tension and therefore more RPM's. As far as the carburetor adjustment (if there is any), this will be one to one and one-fourth turn out from seated. Let us know how you make out! If you happen to have a rider, write back and i'll walk you through any possible problems.

 
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04-09-04, 12:27 AM   #8  
Ecxellent puey61!

You beat me to it.

Chris,

I agree...I think your governor tension has been knocked out of adjustment somehow. What HP engine is on it?


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

God bless!

 
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04-09-04, 06:35 AM   #9  
Yes, I do have alot of bushes, and it is a walk behind mower. This governor attachment your talking about, it is attached directly to the carb, right? I just want to make sure that you are not talking about the one that connects to the handle lever.

Also, the mower is a 22" Murray walk behind with a Briggs and Stratton engine.

Thanks

 
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04-09-04, 06:50 AM   #10  
Well, it looks like that was the problem. It's pretty surprising that the piece of metal on the governor arm is so easy to bend. I suppose its kind of guess work how much I should adjust it, I'm just going by sound.

Thanks everybody for your help.

Chris

 
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04-10-04, 01:06 AM   #11  
Glad you were able to get it fixed!!! Thanks for letting us know how it went!


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God bless!

 
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04-10-04, 09:29 AM   #12  
Glad you got it fixed!

 
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