Kaw FH721v surging

[Bulldogparts]

I have adjusted the valves, adjusted the governor, and thoroughly cleaned all linkage. And rebuilt the carb. It will not run unless 1/2 to full throttle, and is surging constantly. I cannot set the idles while it’s running like this. Have I missed something?

The original problem was once hot, it would act as if it was starving for fuel under a load, and was surging. I could choke it, and it would pick up and run a few more feet, then try to cut off again.

Thanks............and Hello from Georgia!!

 

[bertsmobile1]

Hook up an alternative fuel tank ( pinch it off your push mower ) to the fuel pump.
Problem goes away = debris in the fuel lines or tank.

 

[Bulldogparts]

Hook up an alternative fuel tank ( pinch it off your push mower ) to the fuel pump.
Problem goes away = debris in the fuel lines or tank.

Trash was the first thing I checked for. I’m a fair wrench, and started with the simple things.......I’m also cheap. :smile:.

It’s not starving for fuel now. Just surging and won’t idle low.

 

[bertsmobile1]

There is a big difference between clean and really clean.
We are trying to diagnose your problem, some thing a mower shop charges you for, with nothing but the words you post.
There fore we treat the problem as if the poster has a problem working out which end of a screwdriver does the work.
Thus whatever you have already done must be treated as suspect, that is the way it works, if it offends sorry.

You have a surging problem

99.99% of the time surging is caused by a lack of sufficiant fuel to sustain high speed running.
So there is either an air leak after the main jet venturi or these is a restriction in the fuel supply.
We all have different ways of doing a daignosis if the method I asked you to do is either too onerous for you to do, or you feel I am challengineg you mechanical manliness so wont do the test , that is fine by me.
There are others who really want help and are willing to help us help them

 

[Bulldogparts]

There is a big difference between clean and really clean.
We are trying to diagnose your problem, some thing a mower shop charges you for, with nothing but the words you post.
There fore we treat the problem as if the poster has a problem working out which end of a screwdriver does the work.
Thus whatever you have already done must be treated as suspect, that is the way it works, if it offends sorry.

You have a surging problem

99.99% of the time surging is caused by a lack of sufficiant fuel to sustain high speed running.
So there is either an air leak after the main jet venturi or these is a restriction in the fuel supply.
We all have different ways of doing a daignosis if the method I asked you to do is either too onerous for you to do, or you feel I am challengineg you mechanical manliness so wont do the test , that is fine by me.
There are others who really want help and are willing to help us help them

I felt no offense by what was said in any of the previous posts. I am willing to try anything. But I do take offense to your tone. You come off as a total prick, and I would appreciate you keeping your asinine remarks to yourself. If you’re the only one on here who cares to answer, I’d just as soon keep the problem I have.

 

[Bulldogparts]

Now, for anyone else who may chime in.....I have thoroughly cleaned both tanks, i.e. emptied them and rinsed both well. I have blown through the fuel lines with compressed air, and replaced the fuel filter. The fuel pump is pumping fuel, and I have checked for air/vacuum leaks using starting fluid sprayed around the carb area while running, with no change in engine speed or sound. I cut grass with it this past weekend. It seems to lose most of the surge when at full throttle AND under a load...mowing. If I stop, the surging is WAY more pronounced. Anyone else have any other suggestions?

Thanks.

 

[BlazNT]

From what you are saying the idle circit of the carb is still dirty. When I clean a carb I always use some strands from speaker wire to run through all the holes in the carb. I mean every hole no mater how small. I run the wire from the throat of the carb to the bowl of the carb. We know the obstruction can go that way as that is the way it entered the carb. Hopefully this will fix the remaining issue for you.

 

[cpurvis]

Sounds like a vacuum leak to me.

edit: Oops, I missed the part where you already checked for air leaks.

 

[Bulldogparts]

From what you are saying the idle circit of the carb is still dirty. When I clean a carb I always use some strands from speaker wire to run through all the holes in the carb. I mean every hole no mater how small. I run the wire from the throat of the carb to the bowl of the carb. We know the obstruction can go that way as that is the way it entered the carb. Hopefully this will fix the remaining issue for you.

I soaked it in carb cleaner for a week while waiting on parts. I blew out everything, and like you said have ran wire into all the holes I can get one into. I’m NOT being a smart *** saying this, but I have checked everything for being clean. I do all of my work on my cars, truck, motorcycles—6 of them, and used to rebuild automatic transmissions for a living. I understand what to look for in most instances, but I admit I’ve never fooled with mower engines much. I have read online service manuals, followed advice of online forums, watched YouTube videos, etc. I cannot get this thing to idle correctly. Like I said before, from 1/2 throttle to WOT, it stays running, and I have cut grass for over 3 hours with it. But it still surges heavily when NOT under a load, and will not idle below 1/2 throttle. Under a load at full throttle, I can still feel it, but it’s not as pronounced.

 

[cpurvis]

If you control the throttle shaft manually (with your fingers), can you make it idle normally? If the engine can be made to run right with you acting as the governor, that points the finger at the governor.

OTOH, if it won't run normally with you acting as governor, seems to me it's the carb or a vacuum leak.

Another thing: Missing a spring on the carb linkage?