Small Engines (Lawn Mowers, etc.): SURGING OHV INTEK B&S, lean condition, fuel filter

Question
Hi Michael, I have a 2004 model Troy Built Tractor with the 21HP OHV Intek Engine. I have replaced the Fuel Filter, changed the oils, checked and gapped the plugs and flushed the fuel tank after finding three spiders in the old fuel filter. I replaced the fuel filter with an authorized double capacity. Well, it's still surging. I looked at the governor spring and it looks fine. The engine has about 100 hours on it. Any ideas? Thanks, Mark

Answer
Hi Mark,

The spring may be weak, even though it looks good.  If the carb is hunting, (rpm's cycling up and down) another cause sometimes is a carb float that is set too low, causing the bowl to become low then refill.  
If the carb is surging (rpm's running away, too high) then I would suspect a leak at the carb-to-block gasket, causing a lean condition.

Let me know what you find.
Michael