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Help with zero turn mower, running rough

blthomas

blthomas

Rusty junk hunter
Joined
Sep 29, 2020
Member Number
2903
Messages
67
Loc
Foothills of the Blue Ridge Mtns
Picked up what I thought was a decent zero turn from some elderly folks I am associates with. Old co-op fuel customers. He died she's downsizing, I just bought a yard.

Its a cub cadet unit. Kawasaki 23hp FR691v engine. It was clean in a shed, supposedly well maintained.

I checked the oil, it kicked right over. Paid the lady. Ran excellent first couple months.

Seemed to start running a bit rough under load few weeks back. I made a mental note to give it all a once over, and do a service soon.

Yea I forgot and it started running rougher under load. Black smoke when cutting. Lower power.

Found the air filter to be trash. Probably original. :shaking:.

Shame on me for not checking sooner. It was packed. Changed it and the fuel filter.

Pulled the plugs, both decently fouled. Cleaned and regapped those.

Started it up, drove okay until putting it under load. Still sputtering/black some. Really couldn't cut with it.

Pulled the carb, got some stuff with spray out but nothing noticeably alarming.

Decided to ohm the original coils. One is at 17k, one at 14.5k. Figured with the discrepancy, I'd slap coils on it. :homer:. Also picked up new plugs.

New coils both are 19k.

I ohm the plugs they are both 4.6k.

I am failing to find proper coil resistance values on the web.

I looked along the kill wire to the coils, and so far can't see breaks. I haven't pulled it completely free, I'm pretty sure the left side is firing, right side is weak/no fire. Its one of those wires where its two wires on the left side, single pigtail to right.

But I've had coils and plugs off and on, so I may be confused as to which side is firing\weak.

Questions would be, I've never messed with small engines much. Could a valve issue have one side running weak? It feels like lack of ignition to me.

Fuel is fresh non eth. Also I cleaned the magnet on the flywheel. Had some flash rust on it.

Plan is to reassemble, re gap coils (using business card), pickup cheap spark tester tomorrow. Maybe swap coils side to side, swap old and new.

Thanks for any insight. I feel like its obvious, but lack of experience has me overlooking it.
 
pull the valve covers and check / adjust. Check all power and grounds. I've had one run like poo before and it was a bad fuse holder. Melted the fuse and wasn't getting full power (12v but low amp)
 
One of my dads mowers did something similar this summer. It was sucking choke closed when he engaged blades, something to do with broken choke linkage or mount on carb.
 
Valves could certainly be the problem. I bought one cheap for the same reason, adjusted the valves on it, and got another season out of it before it dropped a cylinder. It was a Deere, and therefore had something stupid with the motor config that necessitated a ridiculous green paint tax. Sold it as a non runner.

So yeah, adjusting the valves may get you some more time, but probably wise to start looking for sales on a new motor.
 
Change the coils and gap them with a business card. The kawasakis are known for coils going bad. I had to replace mine at 200 hours for the exact same symptoms. Also, pull the flywheel and sand any rust off of the coil triggers.

Edit...just saw where you did change them. I bought aftermarket coils on ebay first and they were bad right out of the box.
 
Last edited:
70 tp said:
unhook kill wire when troubleshooting
Click to expand...
I've seen safeties with corrosion or just water intrusion cause issues as well, pulling the kill wires will isolate the engine from the machine. I'd still suspect the carb, Amazon replacements are so cheap anymore that rebuilding is almost silly.
 
Appreciate the replies. I did a dry compression test, both cylinders at 80psi roughly. Choke open, throttle was mostly. Figure they are virtually identical.

Probably would've been higher if I had th throttle wide open. Gonna do a leak down tomorrow and check valves and push rods. Can't see shit by the time I get home.
 
Whistlepig said:
Change the coils and gap them with a business card. The kawasakis are known for coils going bad. I had to replace mine at 200 hours for the exact same symptoms. Also, pull the flywheel and sand any rust off of the coil triggers.

Edit...just saw where you did change them. I bought aftermarket coils on ebay first and they were bad right out of the box.
Click to expand...
Rust on the flywheel doesnt matter other than properly gapping the coil if it's really rusty.
 
blthomas said:
Appreciate the replies. I did a dry compression test, both cylinders at 80psi roughly. Choke open, throttle was mostly. Figure they are virtually identical.

Probably would've been higher if I had th throttle wide open. Gonna do a leak down tomorrow and check valves and push rods. Can't see shit by the time I get home.
Click to expand...
Alot of small engines crack open the exhaust valve while at cranking rpm to reduce compression, so a tester won't give accurate readings.

Can't remember on the Kawasaki, been some years since I've worked on one.

Badly adjusted valves also makes for hard starting so get "my starter or battery is bad" but it's really just that it doesn't have enough power at full compression. Would need a way larger starting setup otherwise.
 
Just wanted to update this, I hate it when threads have no ending. :shaking::homer:

I cleaned the entire fuel system. Found some trash in the tank. I didn't try starting it after that, so no idea of any effect.

Cleaned and checked gap on new plugs. Triple checked gap on the new coils.

Pulled the kill wires. She popped some but wouldn't start. I used a cheap spark checker with the window, and the spark was very weak both sides.

Re-mounted and gapped old coils. It started, and after clearing out for a bit runs really good. I reattached the kill wire, still runs good.

I did clean the under seat, clutch, and control arm connections of the kill circuit with carb cleaner and a wire brush. No idea if it helped, but they weren't the cleanest.

Checked valve lash. Didn't try running it so no idea if it mattered.

I think I had multiple problems. The magneto was rustyish. Probably not making full spark.

Those kill connections weren't the best, or worst, but clean now.

The coil gap now, looks more appropriate than when I first started diagnosing.

The fuel system had stuff in it.

Appreciate the help, I'll update if it we have more problems.

Pic attached is stuff from tank. Several strands of it.
 

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