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throttle adjustment briggs & stratton quattro 40 mower engine?

I am getting a fluctuating power on my mower. It seems like it is getting too much fuel and not enough air. Spark plug is very carbonated. The throttle mechanism I do not understand? (I am no motor mechanic) I read another post that said air from the fly motor keeps the butterfly valve open, against the tension of the springs. Seems complex to me. Please can someone help me in easy terms on how I can resolve this? Thanks

Iain
May 2009

Briggs & Stratton Garden Tools, Lawn Mowers Throttle Briggs Stratton Mower

why do ya think my crank is easy to pull one time
and thin the next pull it want pull at all?can you
help me with this problem.

larry
April 2016

This engine is not designed to run slower than a few hundred RPM below maximum. The carb has a built-in fuel pump that only operates properly at relatively high speed. Your motor probably has either missing or weak throttle springs which will lower the RPM. Replace them and adjust the tension so that the speed is up. For a diagram of the carb and springs, check the Briggs & Stratton online user manual maintenence section. Look for file "briggsandstrattonMS5373-GB.pdf".

Gary
October 2009

genuine replacement carburators are only $12, just replace them whole thing for proper performance. and as for the springs they are only $2 each, if you think they may be stretched, replace for piece of mind.

galway bogger
September 2009

Yeah, that pipe is the intake manifold. When I took mine apart to clean the carb (thinking it was the problem) it was broke in half. I mended it with JB weld. However when I was putting it back together I neglected to take note on how the springs when together with the governor and throttle. I am trying to find a diagram.

Marc
June 2009

FUNNY THIS,, I WAS LOOKING FOR AN ANSWER TO THIS QUESTION AS MINE IS DOING THE SAME, I STRIPPED MINE DOWN AND THERE IS A PIPE THAT RUNS FROM THE FUEL CHAMBER TO THE ENGINE, THE PART THAT IS BOLTED ON THE ENGINE WAS CRACKED AND I AM GUESSING THIS IS SUCKING AIR IN ?,I HAVE REPAIRED WITH SOME EPOXY GLUE AND JUST GOING TO PUT IT BACK TOGETHER, BUT WAS LOOKING FOR AN ANSWER ON THE CHOKE MECHANISM ??. STRIP IT DOWN AND HAVE A LOOK SEE IF YOURS IS CRACKED ?

MARK
June 2009