I'd try these, one at a time.
1. Be sure the throttle is fully open. Check to see that the throttle cable is actually pushing open the throttle lever on the engine. If there is a primer button, open the throttle and push it four times slowly before trying to start. Primer buttons often are on the front or side of the engine and have a rubber covering that slowly pushes itself back out after you release it.
2. Be sure the gasoline(petrol) is good. If the mower hasn't run in a month, drain the gasoline and get fresh gasoline. It attracts water and goes bad after a while.
3. Replace the spark plug, it's only a few dollars.
4. Be sure the air filter is clean. It's probably a piece of foam, pulling air into the underside of a metal container on the side of the engine.
Good Luck!
David@gottamethod.com
http://www.Got-A-Method.com
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David
June 2005