4.5 HP Briggs and Stratton Troubbleshooting

[minodm3]

I have a 4.5 HP Briggs and Stratton powered Craftsman lawnmower. I bought it used 4 years ago for $40. Since then it has run great. I've been changing the oil on a yearly basis. Today it again started up great but while I was mowing the gas tank fell off (a bolt got loose and I didn't notice until too late). I got some new bolts that fit, reattached the gas tank, and now I'm having trouble to get it run right. Sometimes it is running way too fast. Other times its just sputtering. Based on my knowledge the difference seems to be slight changes in how its bolted on (its a two screw bolt system and I've tried attaching each first which has produced the varying results that I'm talking about). I changed the spark plug and that doesn't seem to change anything.

Does anyone have any other suggestions or should I chalk this one up to a loss? My gut is the engine isn't bad since it was running great before this gas tank debacle.

Thanks for any advice.

 

[boraticus]

Possibly your governor mechanism was negatively effected when your tank fell off.

Download a diagram for carburetor/governor components.

You probably have a spring controlled governor. Look to see if the spring is properly attached and correctly set/adjusted.

You may have a vane controlled governor. If so, repeat above instructions for that.

Start there and get back to us.

 

[Kamele0N]

With slightly different reatachment of the gas tank......carburator is slightly "ofset"....and because of that governor settings are little diferent...

http://www.briggsandstratton.com/eu/en/support/faqs/adjusting-the-governor

 

[icruse]

I have a Poulan mower with a Briggs & Stratton 550 series I purchased in 5/09. For the first few years from the start I always had eratic idling, even took it back after a week of owning it and they had one of their mower "experts" fiddle with it and it did not help.
Last mowing season began 5/14 I took off the tank and changed the diaphragm, cleaned the carburetor (not really any adjustments to do)and changed the plug. Start it up and it still idles up and back and stutters.
But then I noticed that there is a tab on the gas tank and carb where the idle spring hooks, and I noticed that this tab was bent too far back to where the spring did not have the tension it needed.
So, I bend it to straighten it up; now there is more tension, start it up and it has run perfect ever since.
Don't know if yours is the same, but hope this helps.

Good Day,
Steven

 

[bubbatime]

Yes, as above, find the governor spring. It will be attached to a bendable tab. Bend the tab in both directions until you get it just right.

 

[Finz]

Originally Posted By: icruse
I have a Poulan mower with a Briggs & Stratton 550 series I purchased in 5/09. For the first few years from the start I always had eratic idling, even took it back after a week of owning it and they had one of their mower "experts" fiddle with it and it did not help.
Last mowing season began 5/14 I took off the tank and changed the diaphragm, cleaned the carburetor (not really any adjustments to do)and changed the plug. Start it up and it still idles up and back and stutters.
But then I noticed that there is a tab on the gas tank and carb where the idle spring hooks, and I noticed that this tab was bent too far back to where the spring did not have the tension it needed.
So, I bend it to straighten it up; now there is more tension, start it up and it has run perfect ever since.
Don't know if yours is the same, but hope this helps.



Good Day,
Steven



Good call...!

 

[Merkava_4]

Please post the engine numbers off the blower housing.

 

[lars11]

and that spring may be stretched too from hanging the tank/carb assy.

So check that the spring looks like a new one, also check if you lost the o-ring between the carb and intake. (if you have one of those engines)

 

[old1]

Yup, what lars11 said

 

[Merkava_4]

Originally Posted By: lars11
(if you have one of those engines)


That's just it: How do you know it's one of those engines?

 

[lars11]

Well, I don't. The OP could have provided a photo or more info on the engine. But, it sounds like a failure common to sprint 40 etc engines that are the most used on small briggs mowers...
Originally Posted By: Merkava_4
Originally Posted By: lars11
(if you have one of those engines)


That's just it: How do you know it's one of those engines?