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So I get the mower out this year and have been having all sorts of issues with it.

Charged up battery and installed, put in fresh gasoline.
Fired up fine and pulled it out of shed and set it to medium speed to shut doors on shed.
Engine starts surging and then dies, never done this before.

Fire up again and give it full throttle and seems to be running ok.
Pull blade engage and engine bogs way down and stalls.
Start it back up and head to driveway to look it over.

Add some SeaFoam to gas tank to hopefully help clean out anything in carb.
Start it up and full throttle, engine sounds good, but starts this periodic, like every 10 seconds pretty regularly, dropping power.
Try driving some laps around driveway and it still doing this. Power drops not to the point of stalling, but noticeably lower than full throttle.
What would cause such a regular, periodic drop in RPMs?

I've got a clear gas filter and notice that there's only a trickle of gas in the filter, yet the engine runs just fine.
Is this normal?
Note that I also replaced the gas filter last year along with oil change.

Pulled out air cleaner and blew off filter, wasn't too dirty.
Pulled off air hose to carb and looked in, noticed it was kinda "wet" by choke butterfly, should it be like that or should it be dry in there?

Pulled on blade belt and am able to move blades, but hear grinding from (I think) the PTO clutch? Should it grind like that?
I took a .015 feeler gauge and slipped it in check holes and distance seems to be ok, just a bit of resistance.

Fired it up again and this time it ran without any surging at full throttle.
Tried engaging blades and it bogged down and stalled.
Started up again, full throttle, engaged blades and same thing, bogged down and stalled.
Third times the charm?
Fired up again, full throttle, engage blade and VROOOM, blades spin up just like normal.
Held my breath and did the lawn and mower worked fine.

Scared what next week might hold!

Not sure what to check?
When it works, it works great.

What would cause this intermittent periodic surging?
What would cause it to sometimes die when engaging blades but other times fire them up as usual?

Thanks!

Does it have two coils? I'm thinking a few years ago mine would die when I engaged the blades and it had a bad coil. I'm not even a shade tree mechanic so I may not know what I'm talking about. I took it to the dealer for them to diagnose and repair. Don't have it now, upgraded to a turf tiger. Good luck.

plateauman57 said:

Does it have two coils? I'm thinking a few years ago mine would die when I engaged the blades and it had a bad coil. I'm not even a shade tree mechanic so I may not know what I'm talking about. I took it to the dealer for them to diagnose and repair. Don't have it now, upgraded to a turf tiger. Good luck.

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Mmm... Don't know if it has 2 coils or not. To tell you the truth, I'd have to do some research into what/where the coils are and how to test them.

I guess I could consider myself a shade tree mechanic, but if/when it goes beyond basic stuff, I unfortunately have to turn it over to the real ones.

Thanks for the suggestion though.

:welcome:

Surging is nearly always crud in the carb, blocking off the fuel passages so spraying carb cleaner will do nothing.
You can get a bit of corrosion in the jets over the off season which may or may not break free and either block the carb or pass right through the engine.
Water condensing in the bottom of the carb can also cause similar symptoms.
Not enough to kill the engine outright but just enough to cause rough running.
Then there are problems getting the fuel to the carb, blocked fuel outlets in the tank, fuel lines, fuel filters etc etc.
To run, the engine only needs to supply fuel faster than the main jet can pass it into the engine .

If it is just seasonal degregatin then oft it will clear up and pass right through the engine , if it persists the remove the carb and clean it out thoroughly.

bertsmobile1 said:

:welcome:

Surging is nearly always crud in the carb, blocking off the fuel passages so spraying carb cleaner will do nothing.
You can get a bit of corrosion in the jets over the off season which may or may not break free and either block the carb or pass right through the engine.
Water condensing in the bottom of the carb can also cause similar symptoms.
Not enough to kill the engine outright but just enough to cause rough running.
Then there are problems getting the fuel to the carb, blocked fuel outlets in the tank, fuel lines, fuel filters etc etc.
To run, the engine only needs to supply fuel faster than the main jet can pass it into the engine .

If it is just seasonal degregatin then oft it will clear up and pass right through the engine , if it persists the remove the carb and clean it out thoroughly.

Click to expand...

Yes that's what I've been reading, but what is strange to me is that at times it runs just fine for (at least) an hour.
Other times, it runs in this surging mode.

I can't help but feel like it's something going bad.
I read about coils failing or ignition module issues, but I don't know how to test those.

Thanks!

Buy an Neon tube inline spark tester and slip it on the engine.
It won't hurt the engine, just make sure it is tight on the plug & lead and that they are tied out of the way.
When it starts to play up have a quick look at the tester.
If you miss blocks of spark then you have a short or the coils are going bad.
If it sparks on even while the engine is missing then you have the fuel problem so you have knocked out 50% of what to look at.

Not uncommon for rodents to take residence in & around the engine .
They can chew through wires which then make occasional shorts or build nests that cause local overheathing.

So stop look & listen then get back with what you saw,heard & felt.

bertsmobile1 said:

Buy an Neon tube inline spark tester and slip it on the engine.
It won't hurt the engine, just make sure it is tight on the plug & lead and that they are tied out of the way.
When it starts to play up have a quick look at the tester.
If you miss blocks of spark then you have a short or the coils are going bad.
If it sparks on even while the engine is missing then you have the fuel problem so you have knocked out 50% of what to look at.

Not uncommon for rodents to take residence in & around the engine .
They can chew through wires which then make occasional shorts or build nests that cause local overheathing.

So stop look & listen then get back with what you saw,heard & felt.

Click to expand...

Thanks for that suggestion!
I'll look around locally to pick up a tester.
Hopefully it will show/lead me to the source of the problem.

Your machine is probably an older model and Kawasaki has changed the engine ignition coils twice since the 90s. Kawasaki also changed the spark plug in older engines to better match the newer ignition coils. There is a "Y" electrical harness that connects to the engine ignition coils that terminates into one wire that eventually connects to the key switch. In this "Y" on the engine there are diodes installed which prevent back feed from the coils which when electrically shorted or open will cause different engine running/shut down symptoms.
The electrical clutch should be checked for internal resistance and shorting to ground. Locate and carefully disconnect the clutch electrical connector, with an ohmmeter, check the resistance between the two wires, should be between 2.5-2.9 OHMS. If less than 2.5 OHMS this means that the clutch electrical coil is shorting internally. Also check from each terminal to ground, the reading should be infinity or no resistance. In either case the clutch will need to be replaced.
I recommend that you inspect the entire electrical system one connector at a time looking for corrosion/burning on the connector male and female. This includes the key switch and the cranking relay, the panel with the key switch must be removed to do this. It can be easily lifted after the bolts/screws have been removed which will allow access to the connectors.
Another area of concern is the ground connectors that are located on one of the engine mounting bolts.

Mad Mackie said:

Your machine is probably an older model and Kawasaki has changed the engine ignition coils twice since the 90s. Kawasaki also changed the spark plug in older engines to better match the newer ignition coils. There is a "Y" electrical harness that connects to the engine ignition coils that terminates into one wire that eventually connects to the key switch. In this "Y" on the engine there are diodes installed which prevent back feed from the coils which when electrically shorted or open will cause different engine running/shut down symptoms.
The electrical clutch should be checked for internal resistance and shorting to ground. Locate and carefully disconnect the clutch electrical connector, with an ohmmeter, check the resistance between the two wires, should be between 2.5-2.9 OHMS. If less than 2.5 OHMS this means that the clutch electrical coil is shorting internally. Also check from each terminal to ground, the reading should be infinity or no resistance. In either case the clutch will need to be replaced.
I recommend that you inspect the entire electrical system one connector at a time looking for corrosion/burning on the connector male and female. This includes the key switch and the cranking relay, the panel with the key switch must be removed to do this. It can be easily lifted after the bolts/screws have been removed which will allow access to the connectors.
Another area of concern is the ground connectors that are located on one of the engine mounting bolts.

Click to expand...

Mackie, thanks for all that great information! Very much appreciated.
It's a 2005, so I don't know if that's what you mean by an older model or not?

Could all this be due to battery? I replaced the original Scag battery that would no longer crank with a Sears Diehard 2 years ago.
Thinking back, all this seemed to start after I replaced the battery.
Should I get another original Scag battery instead?

Thanks!

indiggio said:

Mackie, thanks for all that great information! Very much appreciated.
It's a 2005, so I don't know if that's what you mean by an older model or not?

Could all this be due to battery? I replaced the original Scag battery that would no longer crank with a Sears Diehard 2 years ago.
Thinking back, all this seemed to start after I replaced the battery.
Should I get another original Scag battery instead?

Thanks!

Click to expand...

Neither Scag or Sears Make there own batteries.
Don't buy batteries from discount chains (son worked at battery plant Wal-Mart buyers 3rd run batteries)but other than that CCA is most important. Higher the better. Most if not all lawn mower batteries have a 90 day warranty. They are not really built very well(son worked at battery plant). Best thing to do is have the battery tested by a auto parts store. most will do it for free.
You said this happened when you changed the battery. I would look at the battery cables for clean and snug. Find where the negative cable connects to frame and remove clean and reinstall.

BlazNT said:

Neither Scag or Sears Make there own batteries.
Don't buy batteries from discount chains (son worked at battery plant Wal-Mart buyers 3rd run batteries)but other than that CCA is most important. Higher the better. Most if not all lawn mower batteries have a 90 day warranty. They are not really built very well(son worked at battery plant). Best thing to do is have the battery tested by a auto parts store. most will do it for free.
You said this happened when you changed the battery. I would look at the battery cables for clean and snug. Find where the negative cable connects to frame and remove clean and reinstall.

Click to expand...

Thanks for the suggestion. I will check the wires/connections as well.

I can't say for sure the problem is the battery, but just wondering if a bad battery or one that isn't as powerful as an original could cause these types of problems?

indiggio said:

Thanks for the suggestion. I will check the wires/connections as well.

I can't say for sure the problem is the battery, but just wondering if a bad battery or one that isn't as powerful as an original could cause these types of problems?

Click to expand...

I can't say for certain that it is the cause either. But I did have a truck one time that I had to replace the battery cable ends so that the alarm system won't quit going off. You just never know with electricity.

BlazNT said:

I can't say for certain that it is the cause either. But I did have a truck one time that I had to replace the battery cable ends so that the alarm system won't quit going off. You just never know with electricity.

Click to expand...

I had another tractor that I checked the battery, tested it and it wouldn't crank the tractor.
I cleaned off the negative terminal and connector, reconnected everything and then it started right up.

I use the 420 CA/ 350 CCA batteries from Tractor Supply. This is an Exide battery, the sealed type. I have these batteries in three machines and haven't had any problems with them, I do replace them at the beginning of the 4th season. I just replace the battery on my 2008 Tiger Cub, this is the 3rd battery. My Hustler is due this spring being a 2012 machine. Batteries do have a date of manufacture on them.
Your Tiger Cub may be older than you think as Scag does a 24 month production run of most models and where the machine serial number falls into the serial number range will tell you about what part of a 24 mouth run it falls into. The engine also has a build date and location in the code numbers.
As for the Kawasaki engine, I have replaced ignition coils on several Kawasaki twins that were 2006 or older.
The coils have internal solid state components that can fail when the engine is hot. When cold, they check out electrically as OK.
Another problem that I have seen on many older machines is accumulation of dirt under the engine flywheel. One machine that I serviced, I had to remove the flywheel and dig out the caked crud that was baked into the area inside the stator. This engine was overheating both the stator and the ignition coils. After cleaning this engine under the flywheel and the cylinder fins, it would run for about two hours and then quit like the key switch was turned off. At that time I replaced the ignition coils and instructed the customer as to how and when to clean the engine with HP air.

Mad Mackie said:

I use the 420 CA/ 350 CCA batteries from Tractor Supply. This is an Exide battery, the sealed type. I have these batteries in three machines and haven't had any problems with them, I do replace them at the beginning of the 4th season. I just replace the battery on my 2008 Tiger Cub, this is the 3rd battery. My Hustler is due this spring being a 2012 machine. Batteries do have a date of manufacture on them.
Your Tiger Cub may be older than you think as Scag does a 24 month production run of most models and where the machine serial number falls into the serial number range will tell you about what part of a 24 mouth run it falls into. The engine also has a build date and location in the code numbers.
As for the Kawasaki engine, I have replaced ignition coils on several Kawasaki twins that were 2006 or older.
The coils have internal solid state components that can fail when the engine is hot. When cold, they check out electrically as OK.
Another problem that I have seen on many older machines is accumulation of dirt under the engine flywheel. One machine that I serviced, I had to remove the flywheel and dig out the caked crud that was baked into the area inside the stator. This engine was overheating both the stator and the ignition coils. After cleaning this engine under the flywheel and the cylinder fins, it would run for about two hours and then quit like the key switch was turned off. At that time I replaced the ignition coils and instructed the customer as to how and when to clean the engine with HP air.

Click to expand...

Super Mackie! Thanks for all that.
I simply put in a DieHard replacement without doing a lot of research. I'm wondering if it doesn't have enough CCA or reserve power.

Also I now want to check the flywheel and clean anything out of there. Thanks for that info as well!

indiggio said:

Mackie, thanks for all that great information! Very much appreciated.
It's a 2005, so I don't know if that's what you mean by an older model or not?

Could all this be due to battery? I replaced the original Scag battery that would no longer crank with a Sears Diehard 2 years ago.
Thinking back, all this seemed to start after I replaced the battery.
Should I get another original Scag battery instead?

Thanks!

Click to expand...

Usually not the battery as the ignition is self energising.
Some Kohlers ran an externally powered advance unit but I think they have all ben dropped.
The only thing a bad battery can do that affects the running of the engine is not supplying power to the fuel shut off solenoid.

Another reason to seperate your problem between ignition and fuel.
Once you have done that you can start jumping into the engine as Mac has described.

You need to diagnose the probelm first before you run around fixing problems that you do not have and potentially introducing more problems.

bertsmobile1 said:

Usually not the battery as the ignition is self energising.
Some Kohlers ran an externally powered advance unit but I think they have all ben dropped.
The only thing a bad battery can do that affects the running of the engine is not supplying power to the fuel shut off solenoid.

Another reason to seperate your problem between ignition and fuel.
Once you have done that you can start jumping into the engine as Mac has described.

You need to diagnose the probelm first before you run around fixing problems that you do not have and potentially introducing more problems.

Click to expand...

Ok, thanks.

It has no problems cranking the engine and it starts after a few cranks, so perhaps it's not the battery.
It's also been acting funny on startup, as it fires right up, runs for a few seconds, then dies.
It did this 2 or 3 times before it fired up and stayed running, then it ran ok.

I checked it yesterday and there was over 12 volts on the battery while the mower was off.
At full throttle, there was like 14.29 volts, so I think the charging system is working...

I took the cover off the engine and looked around,, but didn't find anything.
Both cylinders and coils were very clean, no gummed up grass or leaves or anything.
I checked the connection to the coils and they seemed fine.
I also checked the ground wire where it meets the engine block and that is solid.
I also removed the ground wire from the battery and wire brushed both the terminal and connector, both are now shiny clean.

I popped off the blade belt and spun all of the various pulleys and they all spun easily.

I took the mower back out to the shed and engaged the blades and they spun up ok.
I did this 3 or 4 more times and it didn't bog down or stall.
After I shut the blades for the last time, back came the surging engine.
I found that if I play with the choke, I can get it to a point where it's not surging anymore.

I would think if there was dirt in the carb, that it would run like crap all the time and not just sometimes?

Could it be something going on after the engine warms up a bit?

Thanks!

Loose carb mounting bolts can do that.
As stated earlier surging is caused by insufficient fuel being supplied to the cylinder, so the engine slows down which causes the govenor to open the throttle wider to increase the speed.
During the slower running the float bowl fills up and an opening butterfly puts a strong signal on the venturi so it sucks more fuel and accelerates, then runs out of fuel and decelerates and the whole process repeats itself at infinitum.

Surging is fuel related about 99.9% of the time.
The other 0.1 % it is a fualty govenor.
Start the mower and when it is playing up put your finger on the govenor arm and slowly accelerate the engine.
Somewhere better than 1/2 way open you will find the engine starts to miss and it should sound just like it is running out of fuel because that is exactly what it is doing.

Partially closing the choke restricts the amount of air that can enter the engine so it balances the lack of fuel with a lack of air.
When you engege the blades you put a big load on the engine, both physically from spinning up the deck but electrically as well due to the current draw of the PTO clutch so the engine slows down which causes the govenor to open the throttle fully which allows extra fuel to enter the engine which accelerates initally then runs out of fuel so it slows down again so the govenor allows the carb to open fullly which causes a momentary rich running ( how it accelerates ) but there is not enough fuel to maintain the faster running or the fuel passage is obstructed so not enough fuel can flow so it slows down again.

Gum ( or varnish if you like ) on the side of the float valve can cause similar symptoms as it gets stickier at higher temperatures.

bertsmobile1 said:

Loose carb mounting bolts can do that.
As stated earlier surging is caused by insufficient fuel being supplied to the cylinder, so the engine slows down which causes the govenor to open the throttle wider to increase the speed.
During the slower running the float bowl fills up and an opening butterfly puts a strong signal on the venturi so it sucks more fuel and accelerates, then runs out of fuel and decelerates and the whole process repeats itself at infinitum.

Surging is fuel related about 99.9% of the time.
The other 0.1 % it is a fualty govenor.
Start the mower and when it is playing up put your finger on the govenor arm and slowly accelerate the engine.
Somewhere better than 1/2 way open you will find the engine starts to miss and it should sound just like it is running out of fuel because that is exactly what it is doing.

Partially closing the choke restricts the amount of air that can enter the engine so it balances the lack of fuel with a lack of air.
When you engege the blades you put a big load on the engine, both physically from spinning up the deck but electrically as well due to the current draw of the PTO clutch so the engine slows down which causes the govenor to open the throttle fully which allows extra fuel to enter the engine which accelerates initally then runs out of fuel so it slows down again so the govenor allows the carb to open fullly which causes a momentary rich running ( how it accelerates ) but there is not enough fuel to maintain the faster running or the fuel passage is obstructed so not enough fuel can flow so it slows down again.

Gum ( or varnish if you like ) on the side of the float valve can cause similar symptoms as it gets stickier at higher temperatures.

Click to expand...

Thanks for the dissertation on how it all works. I've never really understood how the governor works to maintain the speed of the engine during increased load.

It sounds to me like the gum/varnish may be the culprit, as it does seem to have got worse after the engine warmed up a bit.
Could it be that there's a period between cold engine/hot engine where it's most sticky, I wonder?
The reason I ask is that the other day, after running the engine for a while and it started this bogging down business, after I got the blades going the mower worked for the next hour without bogging and I was able to cut the lawn.

Thanks!

Just for an idea how decieving this "when hot" idea can be.
The landlord runs a fleet of 2000 series Cubs ( 5 now).
Some of them would run fine for an hour or so then backfire, loose power be impossible to start so we went down the things that get worse when hot route.

Ended up some 100 or so hours latter being nothing more than a plug of grass getting sucked into the fuel tank outlet.
Clean out the tanks on all of them and they have been faultless since.

bertsmobile1 said:

Just for an idea how decieving this "when hot" idea can be.
The landlord runs a fleet of 2000 series Cubs ( 5 now).
Some of them would run fine for an hour or so then backfire, loose power be impossible to start so we went down the things that get worse when hot route.

Ended up some 100 or so hours latter being nothing more than a plug of grass getting sucked into the fuel tank outlet.
Clean out the tanks on all of them and they have been faultless since.

Click to expand...

Funny, I had already added "dump out fuel tank" to my list of things of things to do when the rain stops, just in case there's something in there that's plugging up the outlet periodically and starving the thing of fuel.

On the two that were exhibiting "overheaing" problems. both had casting fins inside the fuel outlet but the Dremmel soon sorted that out.
It was not another suggestion, just an example of some thing that can reoccur at a predictable period and thus get thought of as heat related when all along it was just a running time thing.

bertsmobile1 said:

On the two that were exhibiting "overheaing" problems. both had casting fins inside the fuel outlet but the Dremmel soon sorted that out.
It was not another suggestion, just an example of some thing that can reoccur at a predictable period and thus get thought of as heat related when all along it was just a running time thing.

Click to expand...

Right, that's what made me think of it the other day, that something (bug, leaf, etc.) may have gotten into the tank and sometimes gets down by the outlet and is limiting the flow of gas.

Thanks!

You definitely have a fuel flow restriction anywhere from the tank to carb bowl. Just do the common sense things and the process of elimination will reveal the problem.

I had a 2002 TC with Kaw FH601 engine. Never one tank of fuel went through it without Stabil additive. And 14 years later not one problem related to fuel, ever. Not after storage. Not when hot or cold, etc. Fuel is garbage today; Stabil will not solve all problems, but it will avoid some and reduce others.

BTW - if you want 25hp from that 19hp rated engine, look up my old thread about how to power-up the engine with a very simple carb modification. (PS - as near I can tell from all my research, they are doing the same thing to some of the FX series engines as well ....)

dnewton3 said:

You definitely have a fuel flow restriction anywhere from the tank to carb bowl. Just do the common sense things and the process of elimination will reveal the problem.

I had a 2002 TC with Kaw FH601 engine. Never one tank of fuel went through it without Stabil additive. And 14 years later not one problem related to fuel, ever. Not after storage. Not when hot or cold, etc. Fuel is garbage today; Stabil will not solve all problems, but it will avoid some and reduce others.

BTW - if you want 25hp from that 19hp rated engine, look up my old thread about how to power-up the engine with a very simple carb modification. (PS - as near I can tell from all my research, they are doing the same thing to some of the FX series engines as well ....)

Click to expand...

Yeah, I'm thinking that I'm going to start adding SeaFoam to all tanks of gas to help keep any sludge from building up in there.

I also read that simply running it out of gas isn't sufficient for winter storage, but to also drain the bowl as well, so I'm planning on starting to do that.
I've never done it on anything (tractors, blowers, etc.) before, but I also read that with the added ethanol in the gas today, it makes it go sour faster.

Thanks!

Sea foam won't do you much good if you have an accumulation of grass clippigs & dust in the fuel tank.

bertsmobile1 said:

Sea foam won't do you much good if you have an accumulation of grass clippigs & dust in the fuel tank.

Click to expand...

Yeah, cleaning out the gas tank is at the top of the list of things to do this weekend!

Just a quick update.

Over the past couple of cuttings, I've added gas and also some SeaFoam along with.

Yesterday when I went to cut the lawn, the mower started up fine, no sputtering and seemed to feel somewhat more powerful.
I engaged the blades first time and they spun up no problem, with only a slight bog on the engine.

I think from now on, I'm going to add a bit of SeaFoam to all my stuff, save the cars as I think they turn the gas over pretty quick.

I can't say for sure that this is the resolution, but so far it seems to be pretty beneficial.

Thanks!