On Aug 9, 2:26*pm, "Calab" wrote:
Howdy!

I just received a three year old B&S 3.5 horsepower mower from a friend.
Currently, it starts easy but starts pulsing once it's been running for a
few minutes.

I've been told that the mower ran fine until it was tipped onto it's side to
be cleaned out.

What I've done so far...
*- cleaned the sponge air filter
*- drained the gas and filled with new
*- sprayed the carb with carb cleaner
*- checked oil levels
*- ensured that the throttle moves freely

The only thing that I can think of is that it's internal to the carb, or
that the springs on the carb are not in their correct location.

Photo's of the carb and linkage.

http://members.shaw.ca/linkto/temp/carb1.jpg

http://members.shaw.ca/linkto/temp/carb2.jpg

Any ideas on how to fix this?

Try replacing or cleaning the muffler,I have this to be the problem a
lot of the time.