Kawasaki carburetor issues

This is a little off-topic but I trust you guys over some random small-engine forum. I have a persistent issue with a mower I bought a few years back. This is a Cub Cadet M48 Tank, a light commercial / pro-sumer grade zero turn. It has a Kawasaki FH680V-D29 engine on it. 23HP twin. I got it for cheap ($1000) because it wouldn’t start. We actually managed to start it and drove it right up onto the trailer when I bought it, so I knew it was fixable. The seller informed me he’d just replaced the carb while trying to fix it, but that hadn’t helped. At the time, I thought it mostly needed a new battery for faster crank speeds. Indeed, I have found this motor does not tolerate half-charged batteries.

I wound up replacing several things including the battery, ignition coils, spark plugs, and repairing a blown head gasket. All that helped, but the core issue remains. When I crank it over, I have a 50/50 shot. Either it will fire up instantly and run great, all day (until I stall it or shut it off) OR if it takes a bit longer to fire (cold mornings, too much / too little choke) it floods itself out. An actual puddle of gas becomes visible in the throat of the carb, and the more I crank it the deeper the puddle gets. The only resolution is to unhook the gas line, crank crank crank until the engine finally dries out, and quickly reconnect once it fires up. This usually involves jumper cables since the battery won’t take that much cranking… it gets to be a real pain. But once it’s running, I can go all day no problem. Just don’t stall it out! Warm restarts are impossible, because it floods again on shutdown.

I did occasionally get a warm restart to work, if I pinched off the fuel line to starve the engine on shutdown. I then had a chance to start up before the flooding kicked in.

This engine has a pulse-type fuel pump, powered by engine vacuum. It also has an internally vented carburetor (as is correct by the factory diagram). This is important, because most of what I’ve found online suggests a blocked vent tube will cause these symptoms. However there is no vent tube, as it is internal. So I decided to replace the carburetor entirely, they’re only $40 online now. I installed this tonight, and a new battery as well. Lo and behold, the new carburetor did the exact same thing. Cold crank, choke on, fuel immediately puddles up in the carb intake. It did start once I unhooked the fuel line and cranked awhile. I can see a new starter in my future if I can’t get this fixed… Uggh.

It sure seems like too much fuel is coming in. Like once it’s running, it can “deal with it” because it needs most of that fuel to run. But once it shuts off, the fuel pump spinning down continues to pump it in, and not being burned it just fills up and overflows. Points to a bad needle/seat.

I would think any fuel metering issues are resolved now with the brand new carb. All that’s left is the fuel pump which works fine. New-ish fuel filter. There is no external vent tube. The air filter is clean, I have it disconnected anyhow for these tests (and to see if the puddle is gone). I hook it back up before mowing of course.

Any ideas are welcome, mowing season is fast approaching and I really want to have an easier time mowing. Have any of you run into this?


Yes. But the opposite problem on my FR600V.
If I forget to choke it cold starting; where it will fire right up; then I have to extended crank it cold starting with full choke held. Often after sitting warm to get it to restart I must (what should be unessary) minor choke it.
It is thru the jet-emulsion tube well starving for fuel.
Mine-yours because they do run right says the float/float-levels must be O.K.

Mine I need to remove and clean the positive fuel shut off valve pintle and seat; verify the push up spring. Mine is hanging UP shut:

The flashlight illuminated silver can with two wires under the carburetor float bowl.
Your sounds like a sticking DOWN movement plunger? Did a new fuel shut-off come with the replacement carburetors?
Yours may be open circuit on one of the two control wires. Or circut problem farther up.
You most likely may have a hanging down sticking pintle movement allowing this flooding.

Good análysis on the effects of the engine RPM running down on the crankcase pulsator fuel pump.
These systems are having to balance that; the pulsations in the intake affecting carburetor fuel drawing; and even the effects of the air cleaner back pressure.
I’ve has a few that would not carburate well without an air cleaner element installed.

The later reduced emissions tuned and jetted carburetors the worst for minor effects of Non-E to E10 to Biden allowed E-15 gasolines. Adding better low restrictive air filters and such.
Steve unruh


Another thought.
Mine the high located fuel tank would gravity flow if over half filled.
I’ve recently realized my three diffnert engines with crankcase pulsator pumps are using this pump to control and prevent vapor locking and hot conditions over-fueling by using this pump as a metering device.
I just pulled the to the carb line on mine.
It will only line from the pump dribble, then stop.
If your line to the carb keeps flowing your pump may have internal flapper valves problems.


It appears there is a fuel solenoid on some of those. I would probably look to see if that is what you are supposed to have and if it works properly. The plastic plunger piece can get soft, if it comes off at all (which is easy to do if you are replacing the carb), you are supposed to replace the whole solenoid. The return spring for the solenoid could be weak or the coil may get hot and start to short as well. lf the rubber piece gets loose, it can be the opposite issue where it runs for a while then dies, and the ‘redneck’ fix for that is to snip the end of the plunger off, or replace the solenoid with a bolt. If they snipped the end off, or replaced it with a bolt you might not notice it.


I think old snaggle tooth may have covered this problem. If not, here are some other ones to know about. Eleven video’s and maximum annoyance. Not really related to this but when I was running dual quad on a Chevy 454 I had an electric fuel pump with dial in regulator. It was always screwing up and forcing fuel past the needle valves in the carbs. l thought I needed it for the extra volume but went back to the mechanical pump and problem solved with still enough fuel delivery.


Yes, the shut off solenoid was part of the new carburetor. I can hear it click with the key on/off.

I will try this tonight. It does seem like I have too much fuel incoming, whatever the cause.

I will also try cranking with the solenoid unplugged and see if fuel puddles up. It should stop it completely. If that’s an effective control I could put a switch inline, that could help with startups. Just a workaround though, not a solution.


I have heard of the fuel solenoid plunger gumming up and not moving even though it clicks. Try removing it and re-attaching the wire to se if it moves. You have to grind down an old open end wrench to fit in that narrow space to remove it.
I reread your post and saw that it is a new carb and solenoid. That should not be gummed up - yet.


I was thinking the solenoid didn’t kick open until, you tried to start it, but I could be wrong.
I was told to wait and let the pressure build up in the line ie let the fuel pump shut off prior to starting by the mechanic. If it is a weak fuel pump, then it would be more sporadic based on how full the gas tank is.

If you pull the solenoid, try to engage it and see if it is actually working. Things happen in shipping.


Hello Chris, if liquid fuel is stagnant in the suction pipeline, it is quite likely that the carburetor is preparing a rich mixture that condenses on the cold surface, this is a normal phenomenon when starting from cold. Is the cold start flap controlled automatically or do you operate it manually?
The carburetor has two types of nozzles, low load nozzles and high load nozzles, well, special attention should be paid to the low load nozzles. Here, the fuel is probably pre-mixed with air in the channel, which leads to small holes next to the throttle valve, so that pre-gasified fuel is supplied. This mixture is adjusted by damping the air opening, and a suitable nozzle is easily installed for this purpose. See if the air nozzles have unobstructed access to air.


I thought the link I put in was for all 11 kawasaki videos but it just come up with the cam replacement. You can find all these videos by specifying Kawasaki engine problems on the youtube page for the site.



I would eliminate the pulse pump , i would hang a tank above and gravity feed the engine with fuel and see if that makes a difference if its the same then at least it rules out the pump trying to push too much fuel through .
Dave .
Just another random thought , you could always join the dark side and hook up a charcoal gasifier see how you get on then ! well its one way of eliminating everything :rofl: