Small Engines (Lawn Mowers, etc.): B&S 4.5 Quattro, gas tank, delivery problem

Question
Lawn mower with B&S 4.5HP Quattro starts with out a problem and work sfine for 10 to 15 seconds. After 15 seconds, the engine does not sound smooth. The power seems to continuously vary between high and low like a wave, but the engine does not stall. Please advise what the problem would be and possible solution.

Thank you,
Srini  

Answer
Hiya Srini,
Honestly- this is the most difficult type of problem to diagnose.
1-Start with checking the obvious, change your air filter.
2-Next, look for a fuel leak, go from gas tank to carb inlet.
2-Then check for fuel delivery problem, verify flow out of gas tank is good.
3-The may be an inline fuel filter- just replace it (cheap insurance)
4-Drop the fuel bowl (if this model has one, I can't remember today heh) and check for water or debris.
Stop if any one of these checks solves it- if none do, lemme know and we'll go to the next step!
Good Luck!