Small Engines (Lawn Mowers, etc.): briggs motor, hp briggs, mechanical governor

Question
hello , i have a 15.5 hp briggs vert shaft motor 28n707.motor had gummed up carb when i got it . cleaned seems ok.also had bent intake push rod. straighted for now , to see if motor runs.turns over hard and starts, runs but doesn't rev up to well. can put finger over air cleaner hole and get to rev up and stabilize on gov.
when attempting to drive it slowly dies down and will not rev up to fast position, i can again use finger and get after awhile .
tried another carb from 14.5hp same problem . could problem be burnt valves or possibly bent valves , etc .
looking for help?
thanks rob

Answer
Not likely the valves are the issue and very unlikely you have a bent valve.

What did you set the valve clearance at?

Will the engine rev if you manually move the carburetor butterfly shaft by hand?  You sound pretty mechanically inclined...can you tie a piece of string to the butterfly shaft and move the butterfly shaft by pulling on the string when driving the mower?  Not a high tech solution but the string trick can help get a better assessment of the engines running performance.

If you go to the Briggs website, Customer Support, you can find detailed procedures on adjusting the valve clearance as well as adjusting the governor.  READ the procedures before adjusting the governor or you can break the internal governor arm causing severe internal engine damage.  See the "Adjusting The "Static" Setting On A Mechanical Governor" procedure.

http://www.briggsandstratton.com/support/frequently-asked-questions/Adjusting%20

http://www.briggsandstratton.com/support/frequently-asked-questions/Engine%20Val

Let me know what the valve clearances are.

Eric