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Tact
07-29-2011, 08:15 AM
I have a Cub Cadet with a 25hp Kawasaki FV721V engine. This machine has never given me any major issues since I've owned it for five years. It has approx 125 hrs on it.

Recently, when I cut thicker grass the engine bogs down and stutters so bad that it almost shuts down completely. I have to back up to take the load off and the engine has to catch up to relieve itself. It also started to do this when I made hard turns in the yard. Any kind of load makes the engine want to stall. Even sometime when going up a hill.

I was thinking it might be a bad coil?? Can someone explain how to test the coil and what the readings should be??

I changed the in-line fuel filter and blew out the air filter but was no help.

Any suggestions would be greatly appreciated.

steve4mc
07-29-2011, 11:27 AM
Tact:
Since the point of the coil is to produce a spark at the spark plug, have you checked that you are getting fire to both plugs. Pull the plugs one at a time and put it back in the spark plug boot and hold against a ground (away from the plug hole) and check for spark when you crank it. I always like to hold mine with insulated pliers in case there is a crack in the insulation on the plug wire. If you are not getting spark on one side, then we may need to assume it is a coil. You could then swap coils from one side to the other to see if it follows.

If you have spark on both sides then we go from there down other paths.

Tact
07-30-2011, 10:17 AM
The engine runs fine and performs well until it warms up. That is when it starts to run poorly under a load. So I assume both coils are performing well at the beginning, but one, if not both, start to break down under a load.

Can just testing the coils with a voltage/ohms meter tell me the condition of the coil, or does the coil have to be warmed up, then pulled and tested??

Can someone explain the proceedure in testing a coil and what setting the voltage/ohms meter should be set at?

dutch1
07-30-2011, 10:32 AM
As I recall, Kaw has a CDI ohms test in their service manual but I'm not accustomed to scanning and sending info. If you do a search of the site you can likely find the stuff that The Rob has posted on that subject.

Even then, an ohms test is not necessarily vaiid as it may test OK when cold and break down when it warms up. I keep two inline spark testers and when this dilemma comes up, I put them on the machine, start it up and set out in the sun to run. Listen and observe.

Tact
07-30-2011, 11:07 AM
As I recall, Kaw has a CDI ohms test in their service manual but I'm not accustomed to scanning and sending info. If you do a search of the site you can likely find the stuff that The Rob has posted on that subject.

Even then, an ohms test is not necessarily vaiid as it may test OK when cold and break down when it warms up. I keep two inline spark testers and when this dilemma comes up, I put them on the machine, start it up and set out in the sun to run. Listen and observe.

I guess I need a couple of inline testers, but I don't have any. Might see if Autozone has any.

I tried to do a search, but came up with nothing. Maybe I'm searching with the wrong wording??

dutch1
07-30-2011, 11:33 AM
Try NAPA ----part number 7-05950. If they don't have one in stock, they still show they are available in their 2010 Outdoor Power Equipment catalog. Last I remember they were about 11.00 each.

dutch1
07-30-2011, 11:37 AM
http://www.tulsaenginewarehouse.com/7-05950

Strangely, Tulsa Engine Warehouse shows the same part number. The price is higher than I anticipated, so NAPA may be higher that that.

Tact
07-31-2011, 05:39 PM
I took it to a local mechanic today and described my problem, stating that this mower was bogging down and spitting an sputtering in taller grass. He thought it might just be as simple as sharpening the blades as they appeared to be somewhat dull.

So I let him sharpen the blades, got it home and it is doing the same thing, even in shorter grass. Pushing the levers forward, which puts it in a load situation, this thing just bogs down, almost dieing, but catches it's breath and mows a little further then starts the same thing over and over.

Now I'm thinking it could be a fuel issue. Can the fuel pump on these be bypassed. I think not since the fuel lines are on top of the tanks and joined together with a T.

Any more thoughts besides a possible coil issue???

whosedog
07-31-2011, 07:40 PM
I'm having the same problem on my Wright Stander's 25 HP kawi FH721-v.It only bogs down when it's been running for an hour or more and only when the blades are on.So far I changed the plug,put a new fuel and oil filter and air filter on and changed the fuel pump(only cost $30,used a brigs fuel pump same as Kawi at 1/2 the cost).I sprayed the carb inside and all the linkage on the outside with carb cleaner.If that doesn't fix it, I may take it to the mechanic.Mine has 550 hours on it;I'm thinking replace the carb? Hydro pumps are working good just the engine sputters when under a load.

Tact
07-31-2011, 10:07 PM
Mine mainly bogs down while cutting thicker grass. My grass is zoysia and it is thick, but I've never had loss of power like I'm experiencing. The engine runs fine either idling with blades engaged or not. It even runs fine at high rpm. It just bogs down horribly when cutting thicker grass to the point that it almost stalls out completely. :cry:

If it was a coil problem, would it run so good when idling or at high rpms with the blades engaged while standing still?? This has got my head spinning at it only has about 160 hrs on it.

Tact
08-01-2011, 03:05 PM
Anyone???

This problem sounds more like it is fuel related. Is there a way to test the fuel pump before replacing it or is there something else I need to be looking at??

WJC
08-01-2011, 09:23 PM
Search out the posts by Restrorob, he can tell you how to ohm out the coils. The Kaw engines are known for coil issues and yours sounds like it could be a coil problem since it does it after it warms up.

WJC
08-01-2011, 11:59 PM
Found this one in case you haven't found anything yet.

http://www.lawnsite.com/showthread.php?t=284338

Tact
08-02-2011, 07:44 AM
Found this one in case you haven't found anything yet.

http://www.lawnsite.com/showthread.php?t=284338

I saw that but I'm not sure that I understand the numbers in that table. :dizzy:

I need more layman terminology.

steve4mc
08-02-2011, 04:34 PM
Tact:
It really sounds to me like you are running on one cylinder when this happens. When it goes bad (whether hot or warm), pull off one of the plug wires. If it totally dies, then that cylinder was OK. If nothing changes, that is the cylinder with the problem. THen you can pull the plug out and see if you get spark by holding the plug against the cylinder head away from the spark plug hole. See if the spark is there. If not, it is most likely a coil. IF you have spark, you might have compression issues. In line spark checkers are nice but you can check it without them.

whosedog
08-06-2011, 02:53 PM
Well I fixed my rough running Kawi with a new set of blades. I guess the old ones were not balanced correctly(I sharpen my own but don't have a good blade balancer). Apparently the timing was getting thrown off by the unbalanced blades,I put on a new set and it ran all morning with no sputtering,or hesitation. Thanks for mentioning the blade possibility tact,it was my last shot at repairing it myself before it went into the dealer.Well I guess having a new plug,gas and air filter and fuel pump won't hurt it either,but it was getting 3 balanced blades that corrected the rough running;must have been throwing off the engine timing.It only happened when the blades were on so that was the clue that led to the answer.

Tact
08-06-2011, 04:45 PM
Well I fixed my rough running Kawi with a new set of blades. I guess the old ones were not balanced correctly(I sharpen my own but don't have a good blade balancer). Apparently the timing was getting thrown off by the unbalanced blades,I put on a new set and it ran all morning with no sputtering,or hesitation. Thanks for mentioning the blade possibility tact,it was my last shot at repairing it myself before it went into the dealer.Well I guess having a new plug,gas and air filter and fuel pump won't hurt it either,but it was getting 3 balanced blades that corrected the rough running;must have been throwing off the engine timing.It only happened when the blades were on so that was the clue that led to the answer.

:cool2:

I actually changed both of my plugs and it appears to have corrected a lot of its problems. I ordered a new air filter as well and it should be here in a day or so.

My grass is getting close to needing another cut, so I'll see how it runs going through the zoysia again. I'm keeping my fingers crossed that it was just needing new plugs and a filter.

whosedog
08-06-2011, 04:57 PM
:cool2:

I actually changed both of my plugs and it appears to have corrected a lot of its problems. I ordered a new air filter as well and it should be here in a day or so.

My grass is getting close to needing another cut, so I'll see how it runs going through the zoysia again. I'm keeping my fingers crossed that it was just needing new plugs and a filter.

If you still have a problem, and those are the original blades,at 150 hrs, I would put a new set on.I never would have thought that unbalanced blades would cause the engine to sputter,but after reading what that mechanic told you I thought it couldn't hurt to give it a shot.I change the oil every 40 hours (synthetic Mobil 10 w 30) so I'm hoping to get 2000 hours on that engine,at 500 hours it's just broken in. Thanks!

Tact
08-06-2011, 04:59 PM
I changed blades two years ago to Gator blades. They are in good shape.

ncknaklawns
03-16-2013, 07:26 PM
Was the blades the problem longterm? No issues since?

Tact
03-17-2013, 11:32 AM
Was the blades the problem longterm? No issues since?

If I remember correctly, it was more of the dull blades. No problems last season.

Valk
03-17-2013, 01:06 PM
If there's a coil issue wouldn't the 2 spark plugs look different? The darker plug would likely be the bad side?

I experienced this whole scenario and scratched my head for too long as well...and it turned out to indeed be a bad coil. I could discernibly smell gas in the exhaust when my warmed up KAW 16hp KAI would suddenly seem underpowered and running a bit rough. If I let it sit for awhile it would be back to normal power.


The 2 coils have different configurations...so make sure if you're ordering that you are indeed ordering the correct one.

ncknaklawns
03-17-2013, 07:46 PM
Mine would cough and sputter and if I choked it all the way could almost keep it running but it would try to die ever few seconds, then eventually would or I'd shut it down, wait 10 minutes and then it would run fine again maybe for an hour or two. This repeated from Aug to Nov last year.