briggs and stratton intek runs rough when hot

[plotthound]

my 18hp intek in my sears rider has developed a weird issue when it gets hot.it takes me about an hour to cut my grass and 1/2 way through the engine starts running real rough.sputtering and almost back firing.when it cools off it runs fine again.engine has new oil and spark plug and fresh gas.has the same issue with 91 octane and 87 octane.the vent hole on the gas cap is also clear. hope its not something serious,this machine is about 18 years old. thanks

[SUKI]

One thing to check that I had to happen to me is the plug wire as it may be resting on the exhaust pipe has burned. Mine started acting like yours but it progressive got worst over time.

Also ignition can become heat soaked and act like this too.

[plotthound]

plug wire is fine and far from the exhaust.maybe i will grab a cheap azz coil off of amaon and try that. thanks suki

[Arkie]

Exact engine model and type would help us?

[hanz63]

It sounds like a good excuse to pop the valve cover, check rockers and guide positioning.

[plotthound]

thanks guys,will dig into it a bit deeper when i geta chance.

[plotthound]

i still have not pulled the valve cover off to take a look,but i did give the gas tank a serious dose of my homebrew sea foam.the engine runs 90% better now in the past 2 cuts.gonna give it another good dose and sea if that cures it.not sure what my homebrew did but it did do something.

[38racing]

I had a rider with kill wire pinched. When hot the pinch actually grounded it out.

[plotthound]

well my seafoam doping did not do the trick,will have a look at the kill wire 38 racing.looks like im gonna have to delve into this a little deeper.

[KE4AVB]

As 38 mention check a pinched wire behind the starter. Or might be a heat sensitive coil. Have you checked for spark when it fails. I even had a couple plugs to fail under heated conditions.