FX730V Bogs under load

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ScrappyDoo

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May 27, 2026
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Im about to my wits end. The mower will start and run rough as heck and smoke, then it all the sudden smooths out and no smoke. If I give it a lot of throttle, it goes back to step one and I have to restart. If I slowly add throttle, I can get it to full after 5 minutes or so. Now, if I engage blades, or simply try to drive, its back to step one.

I tried running seafoam in the oil, and changed it after it ran an hour or so. This did seem to help it with the ramp up time.

I have seafoam still in the gas.

I have changed the plugs and coils.

I changed the carb last season and it has very few hours on it.

Fuel pump has been replaced as well as the gas filter.

I will add videos if it will let me. Need some advice you guys, Im about to lose it, and this mower is my baby.

Thanks in advance!
Scrap'
 
check the exhaust spark arrestor screen if it has one.

Make sure you are using plugs acquired locally thru Napa, Autozone etc., and not thru the big online retailers of generic goods. Lots of counterfeits out there. Check the ait filter too. And I am hoping the gasoline is fresh and not more than a couple months old.
 
Check your fuel lines for good flow , when did this start ? all of a sudden or has it been acting up over time ?
New components don't mean they're good , I've put new carbs on thinking that eliminated the carb from the issue and was still the carb, same with fuel pumps etc. It does not sound like an ignition problem .
 
ScrappyDoo said:
Im about to my wits end. The mower will start and run rough as heck and smoke, then it all the sudden smooths out and no smoke. If I give it a lot of throttle, it goes back to step one and I have to restart. If I slowly add throttle, I can get it to full after 5 minutes or so. Now, if I engage blades, or simply try to drive, its back to step one.

I tried running seafoam in the oil, and changed it after it ran an hour or so. This did seem to help it with the ramp up time.

I have seafoam still in the gas.

I have changed the plugs and coils.

I changed the carb last season and it has very few hours on it.

Fuel pump has been replaced as well as the gas filter.

I will add videos if it will let me. Need some advice you guys, Im about to lose it, and this mower is my baby.

Thanks in advance!
Scrap'
Click to expand...
Has this engine been sitting and never started for several years? Is the oil level good and have you smelled it to check for gas in oil?
 
Do a compression and cylinder leak down test. What do the plugs look like? Could be a blown head gasket.
 
ScrappyDoo said:
I tried running seafoam in the oil, and changed it after it ran an hour or so. This did seem to help it with the ramp up time.
Click to expand...
Waste of money here. Still have this issue so the seafoam which was originally made for 2 strokes didn't work, again.
ScrappyDoo said:
I have changed the plugs and coils.
Click to expand...
Do the plugs say Torch on them? Where did you get the plugs from? Makes a huge difference. Same with the coils. Have you tested for spark with an open gap style spark tester? That also makes a difference over the light bulb spark testers.
ScrappyDoo said:
I changed the carb last season and it has very few hours on it.
Click to expand...
OEM Kawasaki or Scamazon? Carb needle and seat plus the float height will need going over on ANY new carb. New doesn't mean new especially for mower parts.
ScrappyDoo said:
Fuel pump has been replaced as well as the gas filter.
Click to expand...
More items that need testing. Do you have a solid fat fuel flow AT the carb inlet? Pull the hose off and pump it into a glass jar so you can see WATER and other trash in the bottom.

Are you still running the original fuel lines? They do deteriorate internally so you can't see any fuel restrictions. Recommend replacing all fuel hose from tank to carb.

Leading us to what could be the main culprit, your fuel can spout. Is your can spout an old open type or do you have a new sealed one with o-rings? Spout on the right should be tossed in the trash. One in the middle is a good one.

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From what the OP wrote, going with the usual, lack of fuel delivery slash improper air/fuel ratio.

Bet it's time to check valve clearance, cooling fins and maybe de-carbon the cylinders per your engine manual.
 
sgkent said:
check the exhaust spark arrestor screen if it has one.

Make sure you are using plugs acquired locally thru Napa, Autozone etc., and not thru the big online retailers of generic goods. Lots of counterfeits out there. Check the ait filter too. And I am hoping the gasoline is fresh and not more than a couple months old.
Click to expand...
Not sure how to test the arrestor, so no.

Plugs are from the big girls in the woods. Although I have Tested at least 6 and all have the same issue.

Air Filters are replaced, but it does this with or without any air filter.

Gas is new.
 
Bertrrr said:
Check your fuel lines for good flow , when did this start ? all of a sudden or has it been acting up over time ?
New components don't mean they're good , I've put new carbs on thinking that eliminated the carb from the issue and was still the carb, same with fuel pumps etc. It does not sound like an ignition problem .
Click to expand...
I replaced the carb last season chasing a similar issue, didn't fix it. That problem I finally chased down to a clogged fuel line at the shut off valve in the lower fuel tank. Once I cleaned that out, it ran the rest of the season, and I mowed at least 4 or 5 times this season.

This kinda came out of no where. I noticed it hesitated when I got a really good load on it ( thick grass) but it cleared out. About 30 minutes later, it did the same in another thick patch and would not recover at all.
 
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