Kawasaki FH721V (25hp mower).. carb issue?

[Murphy625]

I have a Ferris IS2000 with a 25hp Kawasaki FHV721V engine @460hrs.

My port side ignition coil went bad about a week ago so I replaced it..

After replacing the coil, the machine seemed to run fine.. Mowing lawn that had not been cut for a couple weeks, I ran the unit out of gas in the middle of the job.. I've never done that before. It had only run for 45 minutes since replacing the coil.

Ever since, the engine hasn't run correctly.. it idles rough and surges at idle.. I figured it sucked something up into the carb or whatever.

I took the carb apart (Nikki 150037121) and boiled it out really well.. I forgot to count the number of turns on the fuel pilot screws!!! Ouch!

Since putting it all back together, I can not seem to get it to idle as smooth as it used to...

I followed some instructions I found on the web on how to reset the fuel pilot screws and it seems to have helped but the engine is making this Popping sound when its idling.

A casual observer might not even notice the pop pop pop during idle.. Its barely noticeable but its certainly not supposed to make that sound. I can best describe it as a miniature and very quiet backfire. It only does it at idle, the popping almost sounds like Morse Code

The engine seems to have full power at full throttle when mowing and seems smooth.
Even at idle now, the engine rpm's seem to be smooth and steady but there's that popping sound.

One other thing.. Before rebuilding the carb, starting the engine when it was warm was a simple 1/2 second turn of the key.. Now, since cleaning the carb, I have to use the choke.. It starts right up, but the choke has to be on or it will just crank over.

I have my pilot screws set at about 5 turns.

Suggestions?

[RoyM]

Sounds like you still have contamination in the idle circuit. I am not familiar with Kawi but other Japanese engines I have dealt with demand a perfectly clean fuel system. You also may have an intake air leak, spray carb cleaner around any mating surfaces you disturbed.

[Murphy625]

There is no way that carb is still dirty.. I inspected every hole under magnification and sprayed and roto-rootered all the others.. Its been boiled out twice and spray clean as well as compressed air. All passages are clean. Seals are good too.

We suspect a weak fuel pump at this point..

[NO0C]

If you send me an audio file of the Morse, I'll tell you what it's trying to tell you. I'm good up to ~30 WPM.

di dah di dit ----- dah dah dah ---- di dah di dit

Good luck.

[KE4AVB]

Have you set the carburetor idle and governed idle to specs? (1450 and 1550 respectively.)

[Murphy625]

Have you set the carburetor idle and governed idle to specs? (1450 and 1550 respectively.)

We never messed with any governor settings.. All I did was clean out the carb.. And it is clean! All passages were roto-rootered, boiled, sprayed and inspected under magnification.

We suspect a week fuel pump at this point.. Under idle, the fuel just dribbles out of the fuel pump at a fast drip.. absolutely no pressure build up when plug the fuel hose with my finger. New pump is on its way so we'll see.

[KE4AVB]

Once you get the fuel pump. You should get a copy of the engine's service manual.
http://www.mymowerparts.com/pdf/Kawasaki-Service-and-Repair-Manuals/FH451V-FH480V-FH500V-FH531V-FH541V-FH580V-FH601V-FH641V-FH661V-FH680V-FH680V-FH721V-KAWASAKI-SERVICE-REPAIR-MANUAL--99924-2078-01.pdf

Your idle mixture screws are way off.
FH721V Pilot air screw turns out (Idle mixture screw turns out) L: 2 1/4, R: 1 1/4 per service manual for early models and L: 3, R: 2 1/4 for late models.

Also you do realize that anytime you work on a carburetor you can inadvertently change it operating characteristics so the rpms at idle, governored idle and top non load governed rpms needs checking.

[Mek-a-nik]

Maybe a good dose of Seafoam would chase any possible dirt in it.
I think a fuel pump issue would show under load.

[Murphy625]

Once you get the fuel pump. You should get a copy of the engine's service manual.
http://www.mymowerparts.com/pdf/Kawasaki-Service-and-Repair-Manuals/FH451V-FH480V-FH500V-FH531V-FH541V-FH580V-FH601V-FH641V-FH661V-FH680V-FH680V-FH721V-KAWASAKI-SERVICE-REPAIR-MANUAL--99924-2078-01.pdf

Your idle mixture screws are way off.
FH721V Pilot air screw turns out (Idle mixture screw turns out) L: 2 1/4, R: 1 1/4 per service manual for early models and L: 3, R: 2 1/4 for late models.

Also you do realize that anytime you work on a carburetor you can inadvertently change it operating characteristics so the rpms at idle, governored idle and top non load governed rpms needs checking.

Holy crap! I totally missed finding the screw turn settings.. Thank you very much! And on that note, we can't even get it to run at less than 1/2 throttle properly with the screws any less then 3 turns.. at 5 turns it seems to run much better but still not correctly.

I understand the characteristics can change when you work on any carb, but not by the magnitude of what we are experiencing.

I believe its the fuel pump.. I saw a video on Youtube here: https://www.youtube.com/watch?v=HAUZUPoopSI of a fuel pump test.. Same kind of pump we have.. The guy just turns the engine over with the starter and that fuel pours out of that hose. We have only a slight dribble at idle and barely a small stream at full throttle.. and what seems like no pressure at all.

I think the fuel pump diaphragm has stiffened up and I think that's causing it to lose most of its diaphragm stroke.. which would also cause a drop in both volume and pressure. Just a theory at this point but its the best I have.

The carb is clean.. I guarantee it..

[Murphy625]

Maybe a good dose of Seafoam would chase any possible dirt in it.
I think a fuel pump issue would show under load.

The carb is clean.. I doubt seafoam would be of any help.

Good idea about the fuel pump issue under full load.. but what do you think would happen if the diaphragm was just stiff.. lost its elasticity or something like that? I had an old briggs 5hp on a leaf and grass catcher where the fuel pump diaphragm was built into the carb.. taking it apart it looked perfectly good.. but when I got a hold of the rebuild kit and felt the new one, it was obvious the original was much stiffer and less flexible.. The leaf vacuum engine was experiencing almost the same behavior..

Well.. in any case.. the new fuel pump is a $10 waste of money if I'm wrong. We've covered almost everything else so whatever is left must be the solution yes? Or at least I hope so..