Small Engines (Lawn Mowers, etc.): 6.5 HP Briggs and Stratton, briggs and stratton, hp briggs

Question
QUESTION: I have two push lawnmowers, both have 6.5 HP B&S engines.  One leaked gas from the carb, the other would start after pulling multiple times but die immediately.  The one that leaked gas would run, but after shutting it off would leak gas.  I have taken both carbs off and cleaned them the best I could, all jets seem to be clear.  Anyway, I took the float off of the non running carb and put it on the leaking carb.  That carb has stopped leaking.  The mower runs, but "lopes" while running.  It cuts fine, but there is obviously something wrong still.  To date, I have did the carb float, new air filter and new plug as well an oil change.  I also just replaced the gasket between the carb and air filter housing as that was missing and I read that may cause the loping, but that didn't help.  Any help on what may be causing the "lope"?  Thanks!

ANSWER: Most surging is caused by dirty carburetors.  Did you blow compressed air from an air compressor through all the carburetor orfices?  Sounds like the carb high speed circuit may be partially clogged.  Is the jet in the float bowl nut clean?

Can you send me the engine model nubmers so I can look up your carb(s)?

Eric

---------- FOLLOW-UP ----------

QUESTION: I did use compressed air on the carb as best i could.  All the jets looked clean as I was able to get a wire through each witn no problem.  The engine number is 123K02-0336-E1  06072056

Thanks again!

Answer
My opinion, but that the best engine Briggs every produced.

Do you have a primer button on your carb system?  Parts list showed a couple of options.

If you have a primer set-up, did you replace the air filter to carburetor gasket?  These things always seem to tear no matter how carefull I am.  

You metioned the o-ring.  I rarely find them leaking but they are cheap to replace and it's wise insurance.

Is the intake tube to engine block gasket sealing?  I have had a couple of times where the screws would loosen or the tube would crack.

While the engine shroud is off to check the intake tube, make sure to clean the governor air as dirt likes to accumulate in the corner.

I've heard of bad governor springs but I have never found one that caused surging.  I still suspect the problem is in the carb but check the other parts.

Eric