My Toro lawn mower starts good, but it only runs for about 5 minutes and shuts off. I have new gas in it and a new spark plug. It is only 3 years old. Also it won't start right away after it quits.

The problem is likely varnish buildup in the carb. Add PAINT THINNER ( yes, I meant to say that !) to the gas. Use 1.5 ounces each of Xylol ( Xylel) and Acetone per 10 gallons of gas ( 5 gal. can will use 3/4 ounce each ).Drain gas tank and carb float bowl. Add fresh gas mixed with thinners. Remove air cleaner element and use quick starting fluid with upper cylinder lubricant to start mower, and keep it running with SHORT bursts of starting fluid until it will run on its own. You may also need to replace or clean air filter if it is old or dirty. continue procedure for 5 minutes or so. Remember to run Sta-bil fuel stabilizer through the system before you shut down for the season, as this will prevent the varnish build up.
I've been using thinner in all of my engines ( gas, pre mix, and diesel ) for a few years with no bad side effects. I've ridden over 15,000 miles on my motorcycle - getting better mileage and power, and not having to buy premium gas either.
Hope this helps!!

It seems to be an obstruction in your fuel delivery system. Get a can of ether and a spray a short burst of it into the breather area near the carburetor, if the mower starts up and then stalls out, then you may need to get your carburetor serviced.

maybe u have to much oil in it or there mite be a stone in the carberator or petrol tank thats blocking the petrol ?

Mine does same. Wait a half hour, restart, runs good for 20 minutes and slows again. Just had it in for a tune up. Machine is only three years old.

your float needle is stuck clean carb

Clean the carb. The old gas gunked up the orifices.

replace the coil

It may have a gravity float residing in the carberator which may be cracked and will show same symptoms.If not garvity float, check for loose connection, heat and vibration my cause it to die, it cools and then restarts.

check the coil by pulling the plug and lay it against the head put the plug wire on pull the handle if it sparks then its not the coil another thing you can try is spay carb clean or starting fluid in carb see if it starts if that starts it then the float in the carb is stuck if i can help further e-mail me @[email protected]

Hello:

There are 2 Possible Causes for this Problem.
1- The Carburetor Requires Soaking and Cleaning.
2- The Valve Clearances Require Setting.
You can View a Breakdown of this Unit at the Following Site Addy.
https://lookup3.toro.com/partdex/default.cfm
Hope this Helps.

Good Luck

Respectfully

John