I have a 50" ZT1 that I bought in August 2020. I used it 3 or 4 times in 2020 and put it away for the winter. This spring, it started right up, but when I engage the PTO to mow, the engine bogs down and then recovers speed over the next few seconds. When mowing however, I have almost no power. The mower comes close to stalling, or actually does stall when turning and going up my yard (with only a slight incline). I replaced the fuel filter and put in fresh gas this spring. The safety switches in the handles and seat all seam to work and cut power if I try something while standing off to the side of the mower. I 'seem' to have full power without the PTO engaged. The spindles all turn, however, I have not taken the belt off to see if they spin freely. I did buy this from the BORG, and am an hour or so away from a larger town that would have a Cub Cadet repair place, plus, this time of year, everyone is so busy that I probably would not get it repaired until August. The mower only has 6 hours on it. Any suggestions as to where to begin diagnosing this? Thank you in advance.
Cub Cadet ZT1 bogs down when engaging PTO
Grahamkmiller
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I have a 50" ZT1 that I bought in August 2020. I used it 3 or 4 times in 2020 and put it away for the winter. This spring, it started right up, but when I engage the PTO to mow, the engine bogs down and then recovers speed over the next few seconds. When mowing however, I have almost no power. The mower comes close to stalling, or actually does stall when turning and going up my yard (with only a slight incline). I replaced the fuel filter and put in fresh gas this spring. The safety switches in the handles and seat all seam to work and cut power if I try something while standing off to the side of the mower. I 'seem' to have full power without the PTO engaged. The spindles all turn, however, I have not taken the belt off to see if they spin freely. I did buy this from the BORG, and am an hour or so away from a larger town that would have a Cub Cadet repair place, plus, this time of year, everyone is so busy that I probably would not get it repaired until August. The mower only has 6 hours on it. Any suggestions as to where to begin diagnosing this? Thank you in advance.
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Air filter was inspected. It looks as clean as the day I brought it home.
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Welcome to the forum!
It sounds a bit like a clogged or dirty high-speed jet in the carb. Making you perhaps run lean when there is a bigger load on the engine, and the throttle plate is open fairly far.
If it has a separate choke control, does adding partial choke help restore any power? If so, that would imply running lean, and a dirty carb.
Carbs can get clogged from gas sitting in them and degrading during the off season. I can only get ethanol gas, which is worse for this. I use fuel stabilizer all the time (cheap insurance, IMO), and I added a $5 fuel shutoff valve. So for winter, I close that, and run the engine until it dies, to get most of the fuel out of the carb. Then it sits like that for the winter.
It sounds a bit like a clogged or dirty high-speed jet in the carb. Making you perhaps run lean when there is a bigger load on the engine, and the throttle plate is open fairly far.
If it has a separate choke control, does adding partial choke help restore any power? If so, that would imply running lean, and a dirty carb.
Carbs can get clogged from gas sitting in them and degrading during the off season. I can only get ethanol gas, which is worse for this. I use fuel stabilizer all the time (cheap insurance, IMO), and I added a $5 fuel shutoff valve. So for winter, I close that, and run the engine until it dies, to get most of the fuel out of the carb. Then it sits like that for the winter.
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I will try the choke this evening. If I understand correctly, you are suggesting I give it a little choke as it is bogging down to see if that helps, and if so, it points towards a dirty carb. Thank you for the suggestion. I will report back.
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Exactly. With no load on the engine, even at full speed, it is largely running on the idle jet, since the throttle plate is mostly closed.
But as the load increases, the throttle plate opens, and now you're running on the high-speed jet. If this one is restricted, you may run too-lean, and lose power.
Adding choke will try to richen up this mixture somewhat. If your power increases, then you can likely say that you aren't getting enough fuel, probably due to a dirty carb.
But as the load increases, the throttle plate opens, and now you're running on the high-speed jet. If this one is restricted, you may run too-lean, and lose power.
Adding choke will try to richen up this mixture somewhat. If your power increases, then you can likely say that you aren't getting enough fuel, probably due to a dirty carb.
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Something else to look for -- A Vacuum leak somewhere. In a hose, a gasket, something like that.
May not be the problem but I always check the cheapest and easiest thing to fix first
May not be the problem but I always check the cheapest and easiest thing to fix first
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That's a valid point. But on a machine that's not even a year old, hopefully it's not something like a cracked rubber hose, etc. And if this problem started after sitting for the winter, that could be consistent with fuel degrading in the carb, restricting flow.
I don't mean to imply I'm arguing. This was just what my thoughts would be, given what's been described.
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I will look into the vacuum leak as well. Although the mower is new, 6 hours, there could have been a mouse-chew or something like that.
Thank you
Thank you
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New stuff breaks all the time. What's puzzling is that, when you get a gummed-up Carb from sitting, a little brake cleaner along with running it for a while usually cleans it out.
Good luck
I think I'd double check for free movement of the mower blades with the deck belt off. The CC deck spindles should rotate absolutely freely, easily with a one finger spin, with no tight spots. Remove the blades and be sure no rope or twine has gotten twisted around the spindle. I found some on one of my blades after only a couple hours of mowing.
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Follow up.
I have had a chance to look into my mower's issues a bit more and have not resolved anything. I pulled the belt and confirmed that all the pulleys turn freely. I verified the air filter is clean. I pulled the input and output in the fuel tank and verified both lines are clear. I pulled the spark plugs and both are gapped properly and look like plugs from an engine with 8 hours on it. I also pulled the carb off and verified that all the passages were open, and that the choke plates both function as they are supposed to. The governor spring is hooked up and the associated plate moves as it should. I pulled the float bowl and that was clean. I was not able to test the solenoid at the bottom of the float bowl as my bench-power-supply is at my other house. The plunger did move easily by hand. I will test this as soon as I get a chance. I also dribbled half a bottle of SeaFoam into the top of the carb, running enough through to almost stall it several times.
I tried engaging the choke while the mower was running, it just choked out and stalled the engine.
To further describe the problem, it seems like it loses power when the load increases. It takes a lot for me to get it to bog down when the mower is running at full throttle and the mower PTO is off. When it is engaged, I can get it to bog down by pushing it too hard, this is more noticeable when going up hill and when making a quick turn, I can stall it very easily, likely due to the increased load while turning. It is not running perfect with the PTO off, but it runs a lot better than when the PTO is engaged. When engaged, I have to be careful not to push it hard enough to stall it.
Any other suggestions.
Thank you
I have had a chance to look into my mower's issues a bit more and have not resolved anything. I pulled the belt and confirmed that all the pulleys turn freely. I verified the air filter is clean. I pulled the input and output in the fuel tank and verified both lines are clear. I pulled the spark plugs and both are gapped properly and look like plugs from an engine with 8 hours on it. I also pulled the carb off and verified that all the passages were open, and that the choke plates both function as they are supposed to. The governor spring is hooked up and the associated plate moves as it should. I pulled the float bowl and that was clean. I was not able to test the solenoid at the bottom of the float bowl as my bench-power-supply is at my other house. The plunger did move easily by hand. I will test this as soon as I get a chance. I also dribbled half a bottle of SeaFoam into the top of the carb, running enough through to almost stall it several times.
I tried engaging the choke while the mower was running, it just choked out and stalled the engine.
To further describe the problem, it seems like it loses power when the load increases. It takes a lot for me to get it to bog down when the mower is running at full throttle and the mower PTO is off. When it is engaged, I can get it to bog down by pushing it too hard, this is more noticeable when going up hill and when making a quick turn, I can stall it very easily, likely due to the increased load while turning. It is not running perfect with the PTO off, but it runs a lot better than when the PTO is engaged. When engaged, I have to be careful not to push it hard enough to stall it.
Any other suggestions.
Thank you
I know you checked the plugs but maybe try to verify that both cylinders are firing with a test lamp? If it has dual coils, one might be cutting out or weak. Just a guess though. You have done about all the checks that are reasonable for an 8 hour engine.
From way out in left field:
Do you have any mouse issues under any of the tins? They don't care how many hours the engine has to cause problems.
Other not so common stuff:
Can you tell if the governor is actually moving the carb throttle when it comes under load? You'd have to get someone to watch the carb linkage when you engage the blades to see if it pushes the throttle up when it starts to bog.
Otherwise, I am thinking RedOctobyr's thought about a clogged passage in the carb might still be an issue. If all else is checked and OK, then maybe completely disassemble, and put the carb in a parts cleaner to boil it all out. Then, using fine nylon string, run them through all of the passages to dislodge anything caught in there. These are small passages. Follow up with spraying carb cleaner into each one using the straw that comes with the can. Follow all that with a blast of compressed air in every place you can get it. Reassemble the carb with new gaskets and give it a new try.
Geez...I certainly hope is is just a bit of junk blocking a carb passage.
Good luck on it.
From way out in left field:
Do you have any mouse issues under any of the tins? They don't care how many hours the engine has to cause problems.
Other not so common stuff:
Can you tell if the governor is actually moving the carb throttle when it comes under load? You'd have to get someone to watch the carb linkage when you engage the blades to see if it pushes the throttle up when it starts to bog.
Otherwise, I am thinking RedOctobyr's thought about a clogged passage in the carb might still be an issue. If all else is checked and OK, then maybe completely disassemble, and put the carb in a parts cleaner to boil it all out. Then, using fine nylon string, run them through all of the passages to dislodge anything caught in there. These are small passages. Follow up with spraying carb cleaner into each one using the straw that comes with the can. Follow all that with a blast of compressed air in every place you can get it. Reassemble the carb with new gaskets and give it a new try.
Geez...I certainly hope is is just a bit of junk blocking a carb passage.
Good luck on it.
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Great troubleshooting work, and thanks for sharing the results! With it being a 2-cylinder, tests to isolate one cylinder at a time seem like a good idea.
I'd disconnect spark plug A, start it, and test it. Shut it down, connect plug A, disconnect B, and repeat. If, for whatever reason, one cylinder is either not firing, or is weak, this non-invasive and easy test will help show that difference.
I'm not shocked that this mostly shows up with the PTO engaged. The blades should take substantially more power than the transmission(s).
I'd disconnect spark plug A, start it, and test it. Shut it down, connect plug A, disconnect B, and repeat. If, for whatever reason, one cylinder is either not firing, or is weak, this non-invasive and easy test will help show that difference.
I'm not shocked that this mostly shows up with the PTO engaged. The blades should take substantially more power than the transmission(s).
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Alien & RedOctobyr. I am going to grab my ultrasonic cleaner and run the the carb in that (I usually fill the cleaner with water, then place the carb in a mason jar full of white gas (Coleman camping gas) in the water. Then I will run a piece of guitar string through the passages and blast them with carb cleaner. I have had great results with that in the past. I will also bench test the solenoid to make sure it actuates under power.
Just for grins, I am also going to take the belt off again and crawl under to make sure there is nothing on the spindles, or the idle pullies. I am also going to pull off the plastic shrouds on the engine and make sure there are no surprise issues in there as well.
Can one of you guys walk me through doing a spark test? I know I did them back in high school auto shop, but it has been a couple of years and I have a great vision of blowing myself up with atomized gas and a spark all in one place...
Thank you again
Just for grins, I am also going to take the belt off again and crawl under to make sure there is nothing on the spindles, or the idle pullies. I am also going to pull off the plastic shrouds on the engine and make sure there are no surprise issues in there as well.
Can one of you guys walk me through doing a spark test? I know I did them back in high school auto shop, but it has been a couple of years and I have a great vision of blowing myself up with atomized gas and a spark all in one place...
Thank you again
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Before touching the carb, check the other stuff, IMO. No need to "disturb" the carb if the problem is a seized pulley or something.
An inline spark tester is a great way to test spark, and also allows monitoring it while running. That's how I found a weak/dying coil. I have one of these, it's a great tool to have available:
www.harborfreight.com
To do it manually without a tester, shut the engine down, and remove the spark plug. Connect the wire to the plug, and lay the metal body of the plug against bare shiny metal on the engine, to ground it. Crank the engine, and look for a bright blue spark.
The risk of fire is very small. Without compression, a fuel mixture is harder to ignite. And with the plug removed, the cylinder is no longer sealed, so most of the air is probably just ambient air moving back/forth through the plug hole, rather than actually being drawn through the valves and carb.
An inline spark tester is a great way to test spark, and also allows monitoring it while running. That's how I found a weak/dying coil. I have one of these, it's a great tool to have available:
In-Line Spark Checker
Amazing deals on this Inline Spark Checker at Harbor Freight. Quality tools & low prices.
www.harborfreight.com
To do it manually without a tester, shut the engine down, and remove the spark plug. Connect the wire to the plug, and lay the metal body of the plug against bare shiny metal on the engine, to ground it. Crank the engine, and look for a bright blue spark.
The risk of fire is very small. Without compression, a fuel mixture is harder to ignite. And with the plug removed, the cylinder is no longer sealed, so most of the air is probably just ambient air moving back/forth through the plug hole, rather than actually being drawn through the valves and carb.
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We bought the same mower for my father and same issues, also I have ran into others same thing, when blades are engaged and mowing it Boggs down.
Odd one:
I recently changed blades on my ZT and although I didn't have any blade engagement issues, found a length of nylon rope wound so tightly around one of the spindles, I had to hack away at it strand by strand, with a box cutter to get it out of there. You couldn't see it from just looking under the deck. Same could be true for any of the pulleys too.
I recently changed blades on my ZT and although I didn't have any blade engagement issues, found a length of nylon rope wound so tightly around one of the spindles, I had to hack away at it strand by strand, with a box cutter to get it out of there. You couldn't see it from just looking under the deck. Same could be true for any of the pulleys too.
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Anyone ever figure out why zt 1 50 cub cadet I bogging down? I'm having exact issues with mine only 10 hours on it and done all things described above
Pipedoc, welcome to MTF, glad you joined.
Do the blades engage ok, but they bog down when mowing or is it that initially engaging the blades bogs the engine down? Are the blades sharp and rotating freely without resistance or any "tight spots" in the full 360 degrees of rotation?
There is some tendency for the engine to bog a bit upon initial engagement as it overcomes the stationary blades and pulleys. If it bogs in mowing, what kinds of grass mowing makes this happen?
Does it stall completely or recover after a short bog down?
If spark is OK, can you recover the engine by using some choke? That might point you to a fuel issue, but at only 10 hours that shouldn't be there unless you got some really bad fuel somewhere.
Do the blades engage ok, but they bog down when mowing or is it that initially engaging the blades bogs the engine down? Are the blades sharp and rotating freely without resistance or any "tight spots" in the full 360 degrees of rotation?
There is some tendency for the engine to bog a bit upon initial engagement as it overcomes the stationary blades and pulleys. If it bogs in mowing, what kinds of grass mowing makes this happen?
Does it stall completely or recover after a short bog down?
If spark is OK, can you recover the engine by using some choke? That might point you to a fuel issue, but at only 10 hours that shouldn't be there unless you got some really bad fuel somewhere.
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