Quantum 5hp dies after about 20 minutes

[slomo]

Carb float levels are adjustable. Using heat, you can bend the plastic tab that pushes on the carb needle.

You need to spend more time testing parts than you do typing.

There is only one spark tester you should be using. Verify your spark.

Air, fuel, spark and compression. You have to prime it to keep the engine running. Tells me a fuel delivery issue. Maybe you need a larger fuel line??

Comparing 2 mowers is a waste of time. Internal parts and their conditions are not the same. The bad running one could have poor sealing valves. You might be checking valve clearance on the WRONG stroke. There is another TDC on most 4 stroke engines. Could have a flat cam or numerous other things.

Lastly you might take some good electrical tape. Wrap the plug wire from the coil to the boot in a healthy layer. Thought was you might have spark leakage when you move the mower. I know you've swapped it all 7 times. Other mower runs with no gas in it.

slomo

 

[smokediver]

I hope you figure it out soon. I got one o a troybuilt pony tiller that will make you pull your hair out. Starts right up, runs fine for a minute or 2 then sounds like it's flooding...but not running rich. Then sometimes it will die and have to run at half choke to run at all.
Carb and tank are clean!
Previous owner even installed a new carb and still acts retarded..

 

[slomo]

I hope you figure it out soon. I got one o a troybuilt pony tiller that will make you pull your hair out. Starts right up, runs fine for a minute or 2 then sounds like it's flooding...but not running rich. Then sometimes it will die and have to run at half choke to run at all.
Carb and tank are clean!
Previous owner even installed a new carb and still acts retarded..

As our resident genius Bertsmobile1 said, there's clean and then there's CLEAN.

A carb can be partially clogged where you can't see it causing your issue.

A new carb means nothing. Most people buy Chinese aftermarket "Gambler Series" carbs trying to save a couple bucks. Then we get to converse with a lot of them trying to get their engine to run proper.

If you have to use any choke at all, after a few seconds, your carb is too lean. Engine is telling you it wants more fuel. Why is it lean? It's dirty with a partial clog internally.

Tillers sit around doing nothing, collecting moisture in the fuel system for how long? Fuel going stale for how long? Is this tiller used daily with fresh fuel added daily? My guess is no. Run the tiller dry before putting it away.

slomo

 

[yardiron]

More than a week later, and the one has somehow fixed itself. It starts, runs, and mows fine since I lost my temper on it and literally beat it on the ground a couple times.
I have three spark testers, one is an inline bulb style, the other is similar to the one in the video above but without the lens, I think its from Snap On, and one called a 'Mag tester', which is basically a spark plug with an alligator clip on one end with two protruding electrodes.
When I say it has no spark, it has NO spark, I can hold the coil wire and spin the motor with the electric starter.

At this point, I have two fixed, one 6.5hp took a carb cleaning, new fuel hose, cleaning the tank, a new coil, and a used flywheel to get it going, it runs okay but its a tired mower otherwise with a 'too short' handle for a big guy.
The second one has a new coil, freshly cleaned carb and tank, and a new fuel hose.
All have new fuel lines, (1/4"), new spark plugs, new blades, and all have had their carbs cleaned, (or replaced). Plus I have a box of new coils, some Briggs and Stratton, a few are Stens.
Those that won't run, have no spark, and have the kill wire removed from the coil.
The Stens coils have gotten spark back in a few while the new BS coils didn't, yet they fire on other motors?
A few of the coils that won't fire on one motor will fire fine on another, but won't run. They fire erratic regardless of the gap or ground.
On those that run and die, they're loosing spark when they die, I can hold the plug wire in my hand, there's no spark. Some run a bit longer, some only a few seconds.

Even if there were a valve issue, its not likely on every one of these, and if there were that big of an issue with the valves or something internal, it wouldn't 'fix' itself in a matter of minutes just sitting there, or come and go at will. It also would not act like an engine running out of fuel when it died.
The one I've been dealing with lately is another 5hp, it has spark cold but loses it after it gets warm. Its got a new flywheel, coil, carb, tank, spark plug, fuel hose, and blade. I pump the primer three times, it starts right up and runs fine. If I let it sit there, it'll run for hours till the tank is empty. If I go to use it, it dies before I make it to the front lawn, just rolling it across the driveway.
It will restart fine, mow a row or two and start to sputter and die. It'll do that three or four times before it refuses to run at all. At that point, it has no spark.
I've swapped the coil and plug 5 times, swapped the flywheel twice, no change. That's by far my best mower in that I like how it mulches the grass.
Yes, I've tried shooting fuel in the carb, it makes no difference, there's no spark. Yes, it has strong compression when it dies. It acts like its running out of gas.
It seems to happen the first time I push the mower forward and pull it backwards, as in mowing under a bush or around obstacles.
It acts as if something is floating in the fuel system and sudden movement causes it to get a taste of water or bad gas, but the tank and cap are new, the carb is new, and the fuel is fresh. There's nothing in the fuel system, I've been over it a dozen times now.
I'm getting close to just yanking the Quantum motor off and sticking an old 3.5hp on that one. None of those have ever given me so much as an ounce of trouble.

 

[bertsmobile1]

From what you have just posted then you either have the wrong coils, defective coils or the wrong flywheel or defective flywheel or have been installing the coils upside down.
Or a combination of any or all of the above.
Downside of using similar castings and flywheels with the same tapper on them is you can fit all sorts of wrong parts.
If it was a twin motor then I would be thinking RF interfearance with the timing chip

 

[slomo]

From what you have just posted then you either have the wrong coils, defective coils or the wrong flywheel or defective flywheel or have been installing the coils upside down.
Or a combination of any or all of the above.
Downside of using similar castings and flywheels with the same tapper on them is you can fit all sorts of wrong parts.
If it was a twin motor then I would be thinking RF interfearance with the timing chip

And possible non resistor spark plugs? My guess is those would interfere with the timing.

slomo

 

[slomo]

More than a week later, and the one has somehow fixed itself. It starts, runs, and mows fine since I lost my temper on it and literally beat it on the ground a couple times.
I have three spark testers, one is an inline bulb style, the other is similar to the one in the video above but without the lens, I think its from Snap On, and one called a 'Mag tester', which is basically a spark plug with an alligator clip on one end with two protruding electrodes.
When I say it has no spark, it has NO spark, I can hold the coil wire and spin the motor with the electric starter.

At this point, I have two fixed, one 6.5hp took a carb cleaning, new fuel hose, cleaning the tank, a new coil, and a used flywheel to get it going, it runs okay but its a tired mower otherwise with a 'too short' handle for a big guy.
The second one has a new coil, freshly cleaned carb and tank, and a new fuel hose.
All have new fuel lines, (1/4"), new spark plugs, new blades, and all have had their carbs cleaned, (or replaced). Plus I have a box of new coils, some Briggs and Stratton, a few are Stens.
Those that won't run, have no spark, and have the kill wire removed from the coil.
The Stens coils have gotten spark back in a few while the new BS coils didn't, yet they fire on other motors?
A few of the coils that won't fire on one motor will fire fine on another, but won't run. They fire erratic regardless of the gap or ground.
On those that run and die, they're loosing spark when they die, I can hold the plug wire in my hand, there's no spark. Some run a bit longer, some only a few seconds.

Even if there were a valve issue, its not likely on every one of these, and if there were that big of an issue with the valves or something internal, it wouldn't 'fix' itself in a matter of minutes just sitting there, or come and go at will. It also would not act like an engine running out of fuel when it died.
The one I've been dealing with lately is another 5hp, it has spark cold but loses it after it gets warm. Its got a new flywheel, coil, carb, tank, spark plug, fuel hose, and blade. I pump the primer three times, it starts right up and runs fine. If I let it sit there, it'll run for hours till the tank is empty. If I go to use it, it dies before I make it to the front lawn, just rolling it across the driveway.
It will restart fine, mow a row or two and start to sputter and die. It'll do that three or four times before it refuses to run at all. At that point, it has no spark.
I've swapped the coil and plug 5 times, swapped the flywheel twice, no change. That's by far my best mower in that I like how it mulches the grass.
Yes, I've tried shooting fuel in the carb, it makes no difference, there's no spark. Yes, it has strong compression when it dies. It acts like its running out of gas.
It seems to happen the first time I push the mower forward and pull it backwards, as in mowing under a bush or around obstacles.
It acts as if something is floating in the fuel system and sudden movement causes it to get a taste of water or bad gas, but the tank and cap are new, the carb is new, and the fuel is fresh. There's nothing in the fuel system, I've been over it a dozen times now.
I'm getting close to just yanking the Quantum motor off and sticking an old 3.5hp on that one. None of those have ever given me so much as an ounce of trouble.

Make sure the two coil mounting tabs are sanded clean with fine paper. And the coil is free of dirt and oil. Lastly the mounting areas are clean to bare metal so it can ground itself and make spark.

slomo

 

[slomo]

I hope you figure it out soon. I got one o a troybuilt pony tiller that will make you pull your hair out. Starts right up, runs fine for a minute or 2 then sounds like it's flooding...but not running rich. Then sometimes it will die and have to run at half choke to run at all.
Carb and tank are clean!
Previous owner even installed a new carb and still acts retarded..

Check for vacuum leaks. Parts heat up and expand. Spray some carb juice around the carb mounts.

slomo

 

[slomo]

Over heating can cause the engine to die in 20 minutes. Clean the engine block, under flywheel and all fins. This is a yearly item in your engine manual. Neglect this and you are looking at engine damage.

slomo