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KAXS.852N4CA spark plugs are very different looking

#1

R

revtim

Recently purchased a 2010 Toro 74923 Z Master Commercial Zero Turn Mower with 1450 hours on it from a municipality. Cut grass twice so far and it was running but not optimally as every now and then it would start revving faster for 10 or 15 seconds and more like I would expect so I am in the process of changing the plugs, fuel filter and air filter. When I pulled the plugs, the rearward plug was clean and dry but the forward plug is black and a little wet. Both fuel filter and air filter needed changing and the fuel filter might have actually been put in backwards to the flow.
I've always see wet/black plugs as a sign of running rich. The tank was full when I picked it up before and this was before mowing season started in Michigan so I am assuming this gas was from last season.
I haven't started it yet as I will get my air filter today. Seems those things aren't carried locally.
The plugs were very difficult to unscrew... providing resistance all the way out so I am also assuming they have been in there a while.
I've never run across this situation except in an engine with low compression in one cylinder but after just 1400 hours that seems unlikely.


#2

StarTech

StarTech

Toro 74923 used a Kawasaki FX751-AS07 engine in all serial numbers.

Never assume anything...I have seen low hour engines to fail.

First do a leak down test to verify cylinder condition. It can be just be just bad valve guide seals as I have seen quite a few times or a blown head gasket. Plus an engine that been overheated could have valve or more that move out of place and crushed the seal.

Even the twin barrel carburetor could have one of the main jets loose as the tiny o-rings do go loose.

And make you are using either 15W50 synthetic or 20w50 dino oil anything lighter does cause problems.


#3

T

txmowman

revtim said:
Recently purchased a 2010 Toro 74923 Z Master Commercial Zero Turn Mower with 1450 hours on it from a municipality. Cut grass twice so far and it was running but not optimally as every now and then it would start revving faster for 10 or 15 seconds and more like I would expect so I am in the process of changing the plugs, fuel filter and air filter. When I pulled the plugs, the rearward plug was clean and dry but the forward plug is black and a little wet. Both fuel filter and air filter needed changing and the fuel filter might have actually been put in backwards to the flow.
I've always see wet/black plugs as a sign of running rich. The tank was full when I picked it up before and this was before mowing season started in Michigan so I am assuming this gas was from last season.
I haven't started it yet as I will get my air filter today. Seems those things aren't carried locally.
The plugs were very difficult to unscrew... providing resistance all the way out so I am also assuming they have been in there a while.
I've never run across this situation except in an engine with low compression in one cylinder but after just 1400 hours that seems unlikely.
Click to expand...
Use a tachometer to see what rpm the engine is running at high idle. Toro’s spec is 3800 rpm. What do the rpm’s jump to when it increases for 10-15 seconds? If it is above the high idle rpm, it is possible that the engine was overheated and the heat damaged the ball guide if the governor assembly.


#4

A

Auto Doc's

Hello revtim,

Sounds like one cylinder not producing power.

A quick check is with a spray bottle to see if water burns off of each exhaust outlet rapidly. If one does not, you found the none working cylinder.

Simple is the best approach: Start by replacing the plugs.

Next would be a possible coil failure. There are many You tube videos that can help replacing one a setting the proper air gap.

If the upper engine cover has never been off for a good cleaning, overheating of the cylinders and a failed head gasket are a real possibility.

Here is a parts source according to your engine number

www.partstree.com

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.
www.partstree.com www.partstree.com

Keep us posted on what you find, because many of us can easily write a lot about "what it could be" but let's take it a step at a time with the diagnostics first.


#5

R

revtim

Thanks for all the input... I should mention that the pan beneath the engine has oil on it...evidence of a leak but don't know from where...
Also, Do the valves on this engine need to be adjusted?


#6

A

Auto Doc's

Hi revtim,

You might check on Ebay and see about getting a manual, CD or download copy, so you have more information to work with. Having the actual repair and service data is far better than some of the wild guess fixes that show up here at times.

I buy most of my small engine and equipment data through Ebay.


#7

A

Auto Doc's

Here is a video by Teryl Fixes All, go to the 5:40 time to skip the BS humor skit, he loves to do them:

Kawasaki FX751-AS07 engine - Search Videos

www.bing.com www.bing.com


#8

Tiger Small Engine

Tiger Small Engine

txmowman said:
Use a tachometer to see what rpm the engine is running at high idle. Toro’s spec is 3800 rpm. What do the rpm’s jump to when it increases for 10-15 seconds? If it is above the high idle rpm, it is possible that the engine was overheated and the heat damaged the ball guide if the governor assembly.
Click to expand...
How can spec be 3800 RPM when maximum for a small engine is 3600 RPM?


#9

Hammermechanicman

Hammermechanicman

revtim said:
Thanks for all the input... I should mention that the pan beneath the engine has oil on it...evidence of a leak but don't know from where...
Also, Do the valves on this engine need to be adjusted?
Click to expand...
All kawasaki engines at around 800 hours needs the govenor shaft seal replaced. There are vids on the tube.


#10

A

Auto Doc's

If it is exceeding 3600 RPM, the governor has been played with in the past or it is failing and sticking. It needs the governor shaft checked for binding or wearing into the engine case and or a correct governor adjustment.

It been years since I have seen a governor shaft binding or badly worn, but it is possible.

Coming from a municipality, anything is possible because most barely service the engines and run them to death. 1450 hrs. of commercial use are high hours in this case.

If lucky, just a new governor shaft seal and proper adjustment will keep this running quite a while longer.

Loosing oil is never a good thing.


#11

R

revtim

Auto Doc's said:
If it is exceeding 3600 RPM, the governor has been played with in the past or it is failing and sticking. It needs the governor shaft checked for binding or wearing into the engine case and or a correct governor adjustment.

It been years since I have seen a governor shaft binding or badly worn, but it is possible.

Coming from a municipality, anything is possible because most barely service the engines and run them to death. 1450 hrs. of commercial use are high hours in this case.

If lucky, just a new governor shaft seal and proper adjustment will keep this running quite a while longer.

Loosing oil is never a good thing.
Click to expand...
Boy.. did I get that wrong. I thought, being a municipality where they have mechanics on staff they would service them more regularly than perhaps a homeowner or business owner where cost was an issue. Shows what happens when I assume something. When I picked it up, the oil was clean and there was a new oil filter which I found consistent with my preconceived notion. Oh well, live and learn.. it's still 100 times better than the ancient old Bunton Zero turn I've been using for the past 7 seasons. I think it dates back to the paleolithic era or.. the early 90's anyway.


#12

S

slomo

Auto Doc's said:
Loosing oil is never a good thing.
Click to expand...
True that.

Oil is cheap though. Keep her on the full mark prior to every mow.


#13

A

Auto Doc's

revtim said:
Boy.. did I get that wrong. I thought, being a municipality where they have mechanics on staff they would service them more regularly than perhaps a homeowner or business owner where cost was an issue. Shows what happens when I assume something. When I picked it up, the oil was clean and there was a new oil filter which I found consistent with my preconceived notion. Oh well, live and learn.. it's still 100 times better than the ancient old Bunton Zero turn I've been using for the past 7 seasons. I think it dates back to the paleolithic era or.. the early 90's anyway.
Click to expand...
Hi revtim,
Bunton is a name I have not heard in a while; they were a very popular commercial brand back in the 80's when I was in Virginia. I'm probably being too harsh on municipalities by comparing them to my area of South Texas.


#14

R

revtim

Auto Doc's said:
Hello revtim,

Sounds like one cylinder not producing power.

A quick check is with a spray bottle to see if water burns off of each exhaust outlet rapidly. If one does not, you found the none working cylinder.

Simple is the best approach: Start by replacing the plugs.

Next would be a possible coil failure. There are many You tube videos that can help replacing one a setting the proper air gap.

If the upper engine cover has never been off for a good cleaning, overheating of the cylinders and a failed head gasket are a real possibility.

Here is a parts source according to your engine number

www.partstree.com

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.
www.partstree.com www.partstree.com

Keep us posted on what you find, because many of us can easily write a lot about "what it could be" but let's take it a step at a time with the diagnostics first.
Click to expand...
Well.. i replaced the plugs, the air filter and the fuel filter and added new gas as well... it ran much better at first, both cylinders that wonderful familiar whirring sound when it is at full rpm.. but then it bogged down again and is now running on one good cylinder and one not so good. The water test on the exhaust took a while to evap the water on the front cylinder but didn't even get wet on the rear one.
So, now I'm wondering about plug wires or coil. Does this have two coils or can one coil give different quality spark to different cylinders? Since it was hitting max revs.. sporatically, this seems most likely to me anyway. I don't suppose it's got a double barrel carb where each barrel supplies one cylinder.
So, your thoughts on this?


#15

R

revtim

Auto Doc's said:
If it is exceeding 3600 RPM, the governor has been played with in the past or it is failing and sticking. It needs the governor shaft checked for binding or wearing into the engine case and or a correct governor adjustment.

It been years since I have seen a governor shaft binding or badly worn, but it is possible.

Coming from a municipality, anything is possible because most barely service the engines and run them to death. 1450 hrs. of commercial use are high hours in this case.

If lucky, just a new governor shaft seal and proper adjustment will keep this running quite a while longer.

Loosing oil is never a good thing.
Click to expand...
Checked after cleaning the pan and it isthe governor shaft seal.. so I can address that.. thanks for the tip.. and the video someone provided gave me the tip I needed. Thanks for this.


#16

A

Auto Doc's

revtim said:
Well.. i replaced the plugs, the air filter and the fuel filter and added new gas as well... it ran much better at first, both cylinders that wonderful familiar whirring sound when it is at full rpm.. but then it bogged down again and is now running on one good cylinder and one not so good. The water test on the exhaust took a while to evap the water on the front cylinder but didn't even get wet on the rear one.
So, now I'm wondering about plug wires or coil. Does this have two coils or can one coil give different quality spark to different cylinders? Since it was hitting max revs.. sporatically, this seems most likely to me anyway. I don't suppose it's got a double barrel carb where each barrel supplies one cylinder.
So, your thoughts on this?
Click to expand...
Hi revtim,

The next logical step would be the coil is breaking down when it gets hot. Coils do cut out and act up that way.

It would not hurt to clean the carburetor well; the fine passages may have some debris in them. Be careful and take pictures if you are not very familiar with carburetors. Clean on the outside is just cosmetic, but cleaning on the inside is what counts. There should be plenty of You Tube videos that will help with your particular carburetor design.

Carburetor can usually be disassembled and cleaned without requiring a fancy rebuild kit. Most just require a new float needle and a bowl gasket seal.

Chemtool B-12 carb spray is what I use or the NAPA Mac's brand. Other cheaper sprays just don't seem to work well, and it is expensive to waste.


#17

A

Auto Doc's

StarTech said:
Toro 74923 used a Kawasaki FX751-AS07 engine in all serial numbers.

Never assume anything...I have seen low hour engines to fail.

First do a leak down test to verify cylinder condition. It can be just be just bad valve guide seals as I have seen quite a few times or a blown head gasket. Plus an engine that been overheated could have valve or more that move out of place and crushed the seal.

Even the twin barrel carburetor could have one of the main jets loose as the tiny o-rings do go loose.

And make you are using either 15W50 synthetic or 20w50 dino oil anything lighter does cause problems.
Click to expand...
Hi StarTech,

Have you ever used Royal Purple 10W-40? That stuff is awesome in air cooled commercial mowers in hot climates. I'm in South Texas, so it is hot around here most of the year.


#18

S

slomo

Any multi-grade will shear down way faster than say SAE 30w will. Briggs and the others say if you use a multi, check the oil more often as it will consume more oil. Not saving anything if you have to use more of it. Just like E-10 gas. Have to use more to get your car the same distance on the same volume of gas compared to E-0.


#19

R

revtim

TO ALL: Well... it turned out that it was one of the coils, the one to the inside facing the seat that was bad. Thanks to the youtube video ya'll directed me to I managed to get it done and it only took me about 4 hours. (keep in mind, I'm 78 years old without a garage and not the most organized when it comes to my tools... so plenty of time following the "measure twice, cut once" philosophy things always take me longer, especially the first time I try something but she purrs like a kitten now... and cuts the long grass like a beast.
I just want to thank all of you that participated in this thread. You've all been so very helpful with ideas and tips.
Next,I'm going to replace the governor shaft seal..I already have the part and just need to get some mowing done before taking on this next task.
I think I'm going to take off the blades and sharpen them too.. can you tell me if the Toro Z Master Pro bolts that hold the blades undo counter clockwise or backwards?


#20

A

Auto Doc's

The blade bolts or nuts are right hand thread (conventional). Use a short board to pin between the blade and deck when you go to break them loose and when you retighten. An air operated or electric impact work very well but make sure the blade is on correct and held in place.


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