Zero Turn power

redneck1952 · May 31, 2021

PuffyC said:
If you pulled the belt and the deck moves fine then at least you know it's an engine problem. Some things I didn't see mentioned:

- Are you sure the throttle linkage is fully opening the carb when at full throttle? If not that would describe what you're seeing.
- Are you sure the choke is fully disengaging when off?
- Could be a vacuum leak somewhere. Might try the WD-40 trick to see if the RPM changes when you spray around hoses and gaskets.
- Could be a bad alternator/regulator, but then your battery would likely eventually die as well. Might be worth checking just to make sure you're seeing over 13v when running and getting a hot spark.
- Are you sure the air filter an intake are clear? Might try pulling it all off just as a test.

If none of that turns up anything I'd do a compression check just to make sure it's right. Since you bought it used there's no telling what kind of shape the internals are in. Maybe you changed the oil and whatever goo the seller put in as a bandaid got dumped, or maybe it was marginal and the original owner was running some high viscosity oil to mask the problem, etc. Not likely but worth a shot if nothing else pans out.

I've checked all pulleys, all free spin without bearing problems
Compression check is 85 per cylinder, not sure what is supposed to be,
Throttle linkage goes to full fuel. removed air filter housing to check and make sure.
Choke verified it is fully open.
Only vacuum that I see on the unit is the air intake.
Items replaced in past.
Carburetor
Air Filter
Fuel Filter
Fuel Pump
Fuel Lines.

Finally got a tach, Engine RPM unloaded is 3650, when blades are engaged it drops to 3200. When mowing I have noticed that it will drop down to 2700 when hitting heavy grass and before it starts to really bog down.

Open for suggestions.

Grumpycat · May 31, 2021

redneck1952 said:
Compression check is 85 per cylinder, not sure what is supposed to be,

85 PSI cranking full throttle is surprising the engine runs at all.

redneck1952 · May 31, 2021

Grumpycat said:
85 PSI cranking full throttle is surprising the engine runs at all.

What is it supposed to be, can't find any information on it.

Grumpycat · May 31, 2021

redneck1952 said:
What is it supposed to be, can't find any information on it.

Usually 120 is service minimum but if your engine has a compression release (most that do are automatic and may not be easy to defeat) then you can not get a meaningful answer from traditional compression testing. A leakdown test is required.

160 is a decent result if a classic compression test is applicable.

Bearsixty7 · May 31, 2021

redneck1952 said:
Finally got a tach, Engine RPM unloaded is 3650, when blades are engaged it drops to 3200. When mowing I have noticed that it will drop down to 2700 when hitting heavy grass and before it starts to really bog down.

Yes that RPM with blades on is too slow! Not sure on the compression test, definitely need to get that verified.
My next thought would be a bad coil or coils.
Have you tried unplugging one spark plug and running on one at a time and see what the RPM's are? Maybe with one side unplugged it will run the same which means that's the cylinder/side with the issue.