I have a Kawasaki 15hp engine that keeps surging. I have cleaned the carburetor several times and everything looks nice and clean. I have also installed a new fuel filter and checked the fuel pump which is pumping a lot of fuel with the line removed. Originally the issue I was having was after about 5-10 min of running it would stall out and have a hard time restarting unless it sat for awhile, but it ran perfect until that point. The issue turned out to be a clogged fuel line. I disconnected both ends front to back (bypassing the pump), and blew out the line. I saw some junk blow out and the line was clear. Now... after doing that it will start up fine but it just surges all the time unless I slightly pull the choke a little. Sometimes it will run smooth as long as the mower blades are engaged, but not always and usually if it's below 3/4 throttle with the blades on it will still surge. I have also checked and bypassed the anti-fire solenoid on the bottom of the carb too with no change.
Is it possible the carb is just bad even though I've cleaned and soaked it several times? Everything else seems to check out.
There is about a .1% chance that there is a gasket leaking between the carb and the intake which maybe found by spraying that area with something like WD-40. The other 99.9% is there is a piece of dirt in the idle circuit of the carb that you haven't gotten out yet. And sometimes takes some work to dislodge and remove. Takes use of thin wired to poke through passages, and backspraying with carb or brake cleaner. For the main jet in the bottom I like to spin a wooden toothpick in those to dislodge any debris. And most of the time the pick will come out black even after running an hour in an ultrasonic cleaner and being sprayed with brake cleaner. That layer of dirt equates to about .1 micron of closure on the main jet and is enough to effect running.
