i was directed here from the bonneville club forum. heres the post.

so my lawnmower wont start. its got fresh gas mixed with a small amt of 2yr old gas + 2 capfuls of chemtool. it wanted to start, so i cleaned out the air filter (looked pretty bad). it coughed, almost caught (it did catch for about a second, then died). so what do you guys think? maybe some carb cleaner down the intake?

let me start off saying i am not an expert. Carb cleaner will tell you if you are getting gas to the firing system. IF it does fire the problem is in the carb. IT probably needs to be cleaned with air and some carb cleaner make sure the jets are not clogged. If it doesnt fire make sure that your spark plug has a nice spark. It was said to me that you need three things for a engine to run compression ( on a lawnmower about 50 psi0, spark, and gas.

putting the 2 yr. old gas in probably didn't help. Even after a couple of weeks gas starts to get crappy and leaves a build up of tarnish, gunk crap. I would drain the gas, get some good fresh stuff.... Clean the carb with carb cleaner and blow out w/ compressed air. Check spark plug & gap, replace if you haven't in a while.

You said that the air filter was pretty bad, that sort of leads to a dirty carb. If something got in their, and is blocking a jet....

Yeah the old gas didn't help... when gas gets old, it can't be revived... it also drops in octane, and will varnish (turns a rancid smell when it starts this) and later on gumms up... alot longer and it'll turn to powder. Carb cleaner down the intake won't do squat in the way of cleaning it.... I'd dump the gas, replace the fuel filter if it has a inline one, take the carb off and apart and blow it out with carb cleaner through any and all holes you see (don't forget the one up that hole the fuel bowl nut went into) If its a float type carb, and compressed air. And retry it....

BUT I would like to know what brand and horse power rating.... they have different carbs for different brands and horse power rating..... if it is a 3.5 briggs classic.... you'd be dealing with a diapragm carb with fuel pickup tubes... simple carb.... if it is a 3.5 briggs QUANTUM, you'd be dealing with a float type carb. Things like that.

And almost forgot, replace the airfilter.