SaltySeminole
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I'm re-powering a Skag mower. It has a Magnum 20 in it now. I found a Magnum 18 in good condition. What is the difference between the two engines other than the horsepower?
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Difference between a Kohler Magnum18 and Magnum 20
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Export threadMad Mackie
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As ILENGINE has mentioned, not much. The MV16, 18 and 20 all have the same exterior dimensions and weight, the crankshaft diameter and length are the critical issue.
The 16 and 18 are almost identical, the 20 has a longer stroke, larger diameter crankpin and piston pin.
The problems that I have run into with Kohler Magnums is the original fuel pumps failing due to ethanol in the gasoline, carbon buildup in the combustion chamber and valves sticking open in the valve guides. As these engines are L head design, valve service is more involved than on overhead valve engines.
Over the years I have run into several small engines that were having running problems due to dust accumulation under the flywheel and causing overheating of electrical components.
Every Magnum that I have serviced had adjustable low and hi speed jets. Engine vibration sometimes will cause the hi speed jet to turn clockwise leaning out the mixture.
Just a few thoughts from Mad Mackie in CT :laughing::biggrin::smile:
Have you determined what is the cause of failure of your MV20?
The 16 and 18 are almost identical, the 20 has a longer stroke, larger diameter crankpin and piston pin.
The problems that I have run into with Kohler Magnums is the original fuel pumps failing due to ethanol in the gasoline, carbon buildup in the combustion chamber and valves sticking open in the valve guides. As these engines are L head design, valve service is more involved than on overhead valve engines.
Over the years I have run into several small engines that were having running problems due to dust accumulation under the flywheel and causing overheating of electrical components.
Every Magnum that I have serviced had adjustable low and hi speed jets. Engine vibration sometimes will cause the hi speed jet to turn clockwise leaning out the mixture.
Just a few thoughts from Mad Mackie in CT :laughing::biggrin::smile:
Have you determined what is the cause of failure of your MV20?
SaltySeminole
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Not yet. Will be working on it this week. Did find one coil mounting bracket broken causing coil to move around.
SaltySeminole
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Not yet. Will be working on it this week. Did find one coil mounting bracket broken causing coil to move around.
I got the Magnum 20 running. It will run for about 15 minutes and then it shuts off. Let it sit for 10 minutes and it will start again. Any advise on what it might be???
bertsmobile1
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Got lots of ideas but before I send you running around like a headless chook.
Pop an inline spark tester on the engine in a place where ou can see it easily while on the mower.
When you hear / fee the engine slowing down watch the tester.
If the tester flashes all the way down to engine cranking speed you have a fuel problem.
Try swapping to the old carb
If it stops flashing or flashes intermittantly then the module has gone.
Again you can swap out the old one
Just hope both are in good nick.
Pop an inline spark tester on the engine in a place where ou can see it easily while on the mower.
When you hear / fee the engine slowing down watch the tester.
If the tester flashes all the way down to engine cranking speed you have a fuel problem.
Try swapping to the old carb
If it stops flashing or flashes intermittantly then the module has gone.
Again you can swap out the old one
Just hope both are in good nick.
Mad Mackie
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Check the vents on the fuel caps. The vents are a small check valve allowing air to flow thru them and into the fuel tanks. They don't allow air or fuel to flow out.
There is a small rubber disc in the vents which in time can deteriorate and the vent itself can become clogged with dust.
Over the years as gasoline with ethanol has been forced on us, I have done some mods to 4 or 5 older Kohler Magnum powered machines to keep them running.
As vapor lock in the fuel supply systems increased with the ethanol gasoline, I have rerouted the fuel supply lines farther away from heat sources such as the engine and the hydraulic pumps. I have also installed a heat insulating sleeve on the fuel lines to further reduce vapor lock problems. The original fuel pumps on these engines have been replaced with a newer style pump which requires the fuel lines to and from these pumps to be replaced and rerouted. If you do replace the fuel pump, bear in mind that it is a mechanically driven pump and the new pump kits have adjustable inlet and outlet fittings. Before installing these fittings, make sure of where they are to be positioned as once installed, they are difficult to remove and reposition and damage to the main part of the fuel pump is very likely.
I also have had to clean the cooling fins and under the flywheels. Two of these Magnums had to have the cylinder heads removed and carbon buildup removed. The carbon buildup heats up as the engine runs and preburns the incoming air/fuel mixture before the spark plug fires. This condition is known as detonation and is a power robbing, engine killing condition.
Kohler Magnum twins are a fairly "bullet proof" engine, that being said, they still need some TLC to keep them healthy and running.
Using gasoline of a higher octane rating than 87 also allows them to run cooler in the combustion chamber.
Clean air filters and a free flowing muffler also helps. As these engines are older, mufflers can rust internally and clog.
I have the Kohler Magnum 16, 18 and 20 engine service manual in pdf in my documents which I can email to you if you would like, PM me if interested.
This manual may be easily available on line, I downloaded it years back, but I don't remember where online.:laughing:
There is a small rubber disc in the vents which in time can deteriorate and the vent itself can become clogged with dust.
Over the years as gasoline with ethanol has been forced on us, I have done some mods to 4 or 5 older Kohler Magnum powered machines to keep them running.
As vapor lock in the fuel supply systems increased with the ethanol gasoline, I have rerouted the fuel supply lines farther away from heat sources such as the engine and the hydraulic pumps. I have also installed a heat insulating sleeve on the fuel lines to further reduce vapor lock problems. The original fuel pumps on these engines have been replaced with a newer style pump which requires the fuel lines to and from these pumps to be replaced and rerouted. If you do replace the fuel pump, bear in mind that it is a mechanically driven pump and the new pump kits have adjustable inlet and outlet fittings. Before installing these fittings, make sure of where they are to be positioned as once installed, they are difficult to remove and reposition and damage to the main part of the fuel pump is very likely.
I also have had to clean the cooling fins and under the flywheels. Two of these Magnums had to have the cylinder heads removed and carbon buildup removed. The carbon buildup heats up as the engine runs and preburns the incoming air/fuel mixture before the spark plug fires. This condition is known as detonation and is a power robbing, engine killing condition.
Kohler Magnum twins are a fairly "bullet proof" engine, that being said, they still need some TLC to keep them healthy and running.
Using gasoline of a higher octane rating than 87 also allows them to run cooler in the combustion chamber.
Clean air filters and a free flowing muffler also helps. As these engines are older, mufflers can rust internally and clog.
I have the Kohler Magnum 16, 18 and 20 engine service manual in pdf in my documents which I can email to you if you would like, PM me if interested.
This manual may be easily available on line, I downloaded it years back, but I don't remember where online.:laughing:
SaltySeminole
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Magnum 20 runs good for 30 minutes then shuts off. Flywheel won't turn. Let sit 20 minutes and it will start up and run for another 30 minutes.
Mad Mackie
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I'm going to say that your engine is overheating for one or more reasons.
1. Pistons may be expanding from high combustion chamber temperatures and sticking in the cylinders. This can be caused by several conditions.
a) Cylinder cooling fins plugged with dirt, fan on the flywheel damaged and not producing enough cooling airflow, carbon buildup in the combustion chamber getting hot and causing detonation which is preburning of the incoming air/fuel mixture before the spark plug fires.
2. The lubricating system is not providing sufficient oil flow and or pressure to keep the engine lubricated and cooled.
a) I have had a problem with some aftermarket oil filters not allowing the lube system to work correctly.
3. Spark timing has changed for some reason.
4. Fuel system has become vapor locked.
a) I have had to replace the fuel pumps on every Magnum that I have serviced in the last ten years.
b) I have had to reroute the fuel supply line(s) to get them away from heat sources to reduce vapor lock problems.
c) Vapor lock will not cause the flywheel to stick.
5. I have had to remove the cylinder heads from some of the Magnums and decarb the piston tops, valves and heads to get the engines to run for more than 20-30 minutes. Also did a valve adjustment while I was doing the decarb. Not the easiest engine to work on however!!!!
1. Pistons may be expanding from high combustion chamber temperatures and sticking in the cylinders. This can be caused by several conditions.
a) Cylinder cooling fins plugged with dirt, fan on the flywheel damaged and not producing enough cooling airflow, carbon buildup in the combustion chamber getting hot and causing detonation which is preburning of the incoming air/fuel mixture before the spark plug fires.
2. The lubricating system is not providing sufficient oil flow and or pressure to keep the engine lubricated and cooled.
a) I have had a problem with some aftermarket oil filters not allowing the lube system to work correctly.
3. Spark timing has changed for some reason.
4. Fuel system has become vapor locked.
a) I have had to replace the fuel pumps on every Magnum that I have serviced in the last ten years.
b) I have had to reroute the fuel supply line(s) to get them away from heat sources to reduce vapor lock problems.
c) Vapor lock will not cause the flywheel to stick.
5. I have had to remove the cylinder heads from some of the Magnums and decarb the piston tops, valves and heads to get the engines to run for more than 20-30 minutes. Also did a valve adjustment while I was doing the decarb. Not the easiest engine to work on however!!!!