FX730v engine struggling under moderate load

[Derpop]

Hey all! I've been fighting with this issue for a few months now and would love to get another opinion on what I can do as I'm at the end of my rope.

I have a Hustler X-One with a Kawasaki FX730v engine in it, and I'm having issues with the engine bogging down under moderate loads. With the throttle wide open, just driving forward at full speed bogs the engine down really bad, and cutting grass of any height is impossible between how bad the motor bogs down from driving, and how it bogs with the blades engaged.

What I have tried so far:

1. Changed air filter (it was fairly dirty, but the change indicator on the mower wasn't indicating overly restricted airflow)
2. Checked for adequate spark with plugs. One looked ok, one looked weak so I replaced both and they looked better.
3. Checked compression. One cylinder measured 68psi, the other was around 90.
4. Leak test. No appreciable leaking from either cylinder.
5. Adjusted valves. One cylinder had a valve a little off, so I adjusted it to match the others.
6. Tried to clean carb. Tried spraying carb cleaner in as directed on the can to avoid disassembling. Didn't help much if at all.
7. Replaced the carb with a new one. Still doesn't seem to have power.

I've got limited time to work on this issue myself and I've exhausted all the obvious troubleshooting steps, and those suggested by the manual I've got. Am I missing something obvious here? Any help is appreciated!

 

[bertsmobile1]

THe usual reason for lack of testicles on a twin is one side dropping out
So the first thing to do is check the temperature of each exhaust pipe after about 2 minutes running
If one is noticably colder than the other then swap the magneto coils
If the problem moves to the other side then that coil is no more in the land of the living.
If the problem stays on the same time then look at valves and make sure both are moving properly.

 

[hlw49]

Air leak at manifold mounting gasket or carb. one side of carb stopped up .

 

[Derpop]

I worked on the engine a little tonight and measured the temperature as suggested by Bert. One side measured~600F, the other side was ~250F. I'll move the coil pack tomorrow to be sure but it seems like that's the issue. I'll report back after further tests. Thanks!

 

[hlw49]

Start it up and spray something around where the manifold mounts to the engine. I use carb cleaner but it could ignite and catch fire. Though I have never had it happen just as a precaution keep a fire extinguisher handy.

 

[bertsmobile1]

Yep,
dud on one side
You might like to swap plugs first & see what happens .
I hat doing unecessary work and swapping coils to find a dud plug falls into that category .
Probably won't be the plug but it only takes a couple of minutes where as getting the blower housing off an FX is a major event , unless you have not cleaned the fins receintly in which case do it now.

 

[StarTech]

If it is anything like the last Briggs that I had a similar problem with it will be a twin barrel carburetor problem as the low temp is firing just not enough fuel to fire properly. Be carefully on disassembly as the main jets may fall out. Also note they are two different sizes. On the one I worked on trash was partially blocking the jets.

 

[hlw49]

Yep,
dud on one side
You might like to swap plugs first & see what happens .
I hat doing unecessary work and swapping coils to find a dud plug falls into that category .
Probably won't be the plug but it only takes a couple of minutes where as getting the blower housing off an FX is a major event , unless you have not cleaned the fins receintly in which case do it now.

Not that big of a deal take the hose off and the bolts the hold the blower housing on and the whole thing off as a unit.

 

[StarTech]

10mm wrench or socket, metric Hex or Torx driver [depends which screws were used on the rotating screen], and probably a heavy brass hammer and large punch [quite useful] would be needed. First the guard and rotating screens needs removed before the shroud can be removed.

I leave others to explain what the hammer and punch would be used for.

 

[Derpop]

Had some time to address this yesterday and it seems to be resolved now, thanks for all your help!

For reference, I tried swapping the spark plugs and the cold cylinder remained the same. I did spray some carb cleaner around the carb and manifold gaskets but there was no change/surging so I went ahead took the engine shroud off.

It was not much of a production, just 3 bolts for each of the fan guards and 5 for the cover itself (and the air cleaner). The coil on the bad side looked really rough/rusty. Replaced both coils just to be sure, and it made an immediate difference. Never did figure out what the hammer and punch were supposed to be for

I proceeded to mow/mulch a ~1acre patch to test, and all was good, no bogging down, all the power in the world available. Actually more power thani remember, I actually think I need to re-adjust the throttle... Thanks again!