Export thread

Exmark Laser Z - starts fine and throttle's up fine, but doesn't have any power when trying to go up a slight incline without mower engaged. I have checked both plugs. ( firing clean, cocoa brown, checked both coils and reset gap. cleaned rust off of flywheel ) It's as if I'm not getting spark advance for the timing to fire on Top Dead Center when engine governor should advance the timing under load. This is the backup machine to my older ( same machine ) which had the same problem and which I just took to the dealer to let them figure it out !! All governor springs are intact. No on has ever touched them ! This machine has a Kawasaki engine, the older one in the dealer shop has a Kohler 27 Hp. I need my backup machine by thursday morning ! Any help would be appreciated !! IrishJO4

There are 7 variations of the lazer Z so for meaningful replies we really need the information off the mowers ID tag.
Assuming the engine is fine and the mower drives strait then your problem suggest a worn belt or insufficient belt tension
Never touched any eXmark but the Toros ( same company ) all have a grease nipple on the tensioner pivot that no one ever seems to bother applying grease to .
The arm must swing freely ( without the spring on ) and not hang up anywhere .

bertsmobile1 said:

There are 7 variations of the lazer Z so for meaningful replies we really need the information off the mowers ID tag.
Assuming the engine is fine and the mower drives strait then your problem suggest a worn belt or insufficient belt tension
Never touched any eXmark but the Toros ( same company ) all have a grease nipple on the tensioner pivot that no one ever seems to bother applying grease to .
The arm must swing freely ( without the spring on ) and not hang up anywhere .

Click to expand...

All belt tensioners are free & greased. Belts are in good condition. The engine is definitely the problem. Now, his other matching machine has the same problem. Both are Laser Z’s 2009 - but this one only has 700 hrs. on it. Engine just started doing this like the other machine- which is at the dealer now. loses power, Sputters, small backfire and then will gain its power back for 50’ and then sputter, small backfire , then RPM’s come up again. This one has original coil’s - both plugs are dry and Cocao
brown on electrode. Running Non-E gas in both machines !! I don’t have all the serial/ model numbers you want. Note- this machine has a Kawasaki engine.

If you run ethanol fuel, then over long-term (winter) storage, as the fuel separates and/or evaporates, it will leave a varnish-like coating on all the carb jets. This shrinks the effective diameter of all the carb jets... which leans out the fuel mixture. Since the engine's power comes directly from burning fuel, burning less fuel directly leads to less engine power. Obviously the smaller jets (the ones hardest to find and clean) clog first.



The carb will not "self clean". Disassembly is mandatory. Cleaning all the fuel paths is difficult.

Prevention is your best weapon. NEVER, EVER leave fuel in any engine with a carb for long periods. Not in mowers, trimmers, tillers, chain saws, etc. Empty all fuel from the tank, lines and carb before storage. No fuel = No problems.

See that blue and green corrosion on the float? Looks like water related corrosion on THAT carb.

Worn belts and pulleys can cause loss of mower speed and as well as blade speed.

Going with never checked valve lash or cleaned any cooling fins.

slomo said:

See that blue and green corrosion on the float? Looks like water related corrosion on THAT carb.

Click to expand...

Yes, there's water. But there's also a brown varnish which will also be on the jets and other passages.

I didn't take the photo, and I wish it was better, but I'm just using what I got.

Born2Mow said:

Yes, there's water. But there's also a brown varnish which will also be on the jets and other passages.

I didn't take the photo, and I wish it was better, but I'm just using what I got.

Click to expand...

Agreed. Sucker is loaded up with varnish.

Still waiting for a reply about which Z we are talking about and YES it does make a difference
Now if one went bad then the other went bad and they are different ages to me that screams BAD FUEL .
For the benefit of others reading this post
NEVER EVER CLEAN THE FLYWHEEL MAGNET
Magnetism goes right through rust , paint , paper , cardboard , dirt etc,etc,etc
You can actually damage the magnets at worst or just waste your time at best .

The problem with ethanol is how it carries water in suspension rather than letting the water sink to the bottom where it can be decanted.

Ethanol carries water into the fuel system where it can do damage from suspension same as not. Corrosion. Varnish. Etc.

Ethanol will not separate from gasoline without being saturated with water.

There is no additive which isn't in effect the same as "more ethanol" to "treat" ethanol in gasoline. If the problem is "separation" then it is a mistake to use an additive which "solves" this problem by allowing more water to be carried in suspension. May end the separation but the water is still there. And when water is present there is less gasoline resulting in a leaner mixture. Same thing happens with premix oil. Engine runs leaner with 40:1 than 60:1.

Sealed automotive fuel systems with evaporative controls have much less trouble with water condensation in the fuel than open small engine fuel systems and gas cans.

GrumpyCat said:

The problem with ethanol is how it carries water in suspension rather than letting the water sink to the bottom where it can be decanted.

Ethanol carries water into the fuel system where it can do damage from suspension same as not. Corrosion. Varnish. Etc.

Ethanol will not separate from gasoline without being saturated with water.

There is no additive which isn't in effect the same as "more ethanol" to "treat" ethanol in gasoline. If the problem is "separation" then it is a mistake to use an additive which "solves" this problem by allowing more water to be carried in suspension. May end the separation but the water is still there. And when water is present there is less gasoline resulting in a leaner mixture. Same thing happens with premix oil. Engine runs leaner with 40:1 than 60:1.

Click to expand...

The water in my photo is obviously from pressure washing by someone who knows zero about engines. That is just one source, and not the source under discussion here.

If ethanol fuel is allowed to sit in the tank and float bowl (typically over the winter), the ethanol WILL most definite separate. This is an acknowledged truth and the entire reason for "fuel stabilizers".
• When the fuel separates (stratifies into 2 distinct layers of gasoline and alcohol), the alcohol layer starts to collect water from the atmosphere. It's the water/alcohol combo that forms the varnish and other growths that close off the jets. Remember, these jets are taking liquid off the bottom of the float bowl and therefore completely immersed in this soup.
• Then, when the owner gets the engine ready for the first running in the Spring, the engine gets a huge slug of alcohol/water which it cannot burn. This immediately fouls both plugs permanently.

So I totally disagree with your assertions and false conclusions.

Born2Mow said:

So I totally disagree with your assertions and false conclusions.

Click to expand...

I totally disagree with your conclusion. Ethanol stays in gasoline until too much water pulls it out. Not the other way around. This is how we test for presence of ethanol: add water, shake it up, and if the “water” level rises then ethanol was drawn out of the gasoline.

Actually, we both agree on the main point: the harmful end results for the small engine owner.
Over time, ethanol fuels stratify leaving a water/alcohol soup (which cannot be separated OR burned in the engine) in the bottom of the float bowl... which can then lead to varnish and other jet clogging secondary effects. The soup, with or without the partially or fully clogged carb jets, then leads to a full array of poor combustion conditions, which may be temporary or permanent.

Two different problems there conflaited into one
Varnish is all of the non volatile parts of fuel left behind once the volatiles have evaporated.
It is not actually varnish but got that name because it looks , feels & smells like the old coating called shelliac which was made by dissolving the grains in metho painting it on then leaving it to dry off .
You rarely get varnish build up from e-10 because the water ethanol "soup" does not readily evaporate ( unless it was 110 deg all month )
There is a lot of stuff in "fuel" that should not be there but is left in because it is too expensive to remove it
Most gets covered by the term "ash content"
Biggest problem with cube carbs because the passageways are just so fine and in some cases the varnish effectively glues check valves open or closed .

Phase separated ethanol/water is a different problem again
Ethanol has been added to bulk fuel ever since the first truck dumped a load of fuel into an underground tank
The air in the tank has moisture in it which condenses into water that drops to the bottom of the tank which can not be removed other than pumping the bottom
A small amount of ethanol will grab a lot of this water and keep it in suspension ( there are additives added to help this happen ) and this water /ethanol mix does in fact burn in your cylinder and increases the cylinder pressure so to a point can be beneficial .
When there is too much water then you get the phase separation which is widely written about .
This is not combustable .
Adding to that is bacteria that were originally in the air end up in this water /ethanol mix where they thrive and reproduce like mad .
The bacteria is a similar strain to the one that gets into diesel tanks and does the same thing
You see this as the milky goop in the bottom of the float bowl
The goop is very acidic so takes the zinc off the electroplated float bowls and that feeds yet another bacteria .
This acid goop is also a good electrolyte so promotes corrosion between the different metal pairs Steel float pin / zinc ( or Al ) body , brass main jet & carb body etc etc etc

Is easy to drain the bottom of a tank of any size. Standard practice during preflight of gasoline powered aircraft.

Or fill it to the brim
No humid air = no water
It is not so much a problem with fuel injected engines because the fuel is drawn out of the tank, runs through the common rail where it picks up heat then gets returned to the tank so for a start, the heat drives off some of the water, then the constantly circulating fuel keeps everything stirred up and finally a small amount of water / ethanol mix will atomise under injector pressure

Since it is, by unanimous decision, such a problem for mower owners.... why isn't there a permanently posted article on this board we can point to when members talk about having this issue. It seems that prevention is so much easier than the cure. So why isn't education on this topic a larger concern on this forum ??