Kohler horizontal opposed twin Magnum 18

Rus A

Member
Joined
Oct 18, 2018
Threads
4
Messages
22
I guess the first thing I need to know is where is the ID tag on this engine? I have it out of the mower and have rolled it over looking with no luck. It is out of a 1985 Deines 1860 zero turn. Thinking I will need engine serial # and Model # before I tear it down. I dont see anywhere that looks like a tag has fallen or been torn off. There is some grease/dirt sticking to it though. Then I am wondering if by unplugging the 3 wire plug coming out of it (for the charging system & engine kill) will allow it to have spark? Also is there a history of the starters on these need repair often? big battery in my truck won't spin it hard enough to engage the starter gear.
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,647
Thanks for starting the new thread.

The starters on mower engines are weak deliberately to avoid blowing up engines cranking them with hydraulic locks.
You have made enough posts to upload some photos so now is the time to do it.
I don't see many magnums let alone twins down here but others should be able to ID them.
The head finning appears to be distinctive
In the mean time, repair manuals are available from here without having to know engine numbers.
https://www.mymowerparts.com/pdf/Kohler-Service-and-Repair-Manuals/
Downloads are free so download both the manuals for the series numbers you got before .
I think the one titled "magnum" is for the single cylinders only, but I have been wrong before.
 

Rus A

Member
Joined
Oct 18, 2018
Threads
4
Messages
22
I bought a service manual for this off ebay. I did tear it down and found a mouse nest against the #2 cylinder. Pulled the heads off and cylinders seem O K even though there was a little bit of water in them for a short time. There was some water in the crankcase oil too. Flushed all cavities out with diesel fuel. My manual gives a procedure using an ohmmeter to check the Ignition module. It appears to test "bad" A genuine replacement is well over $100 but there are aftermarket ones for about 30. Starter would not engage so I removed it and cleaned the exterior, used cleaning solvent on the spiral spline on the drive end. Seems to move much more freely. Before I tore it down I powerwashed anything coated with grease and oil. Still no ID tags other than the "Magnum 18" decal. Manual indicates they only built this engine for 2 years? Anyone know for sure? I listened to one online running with the alternating firing order. Sounds very nice. Cant wait to get it humming like that! Then get it back into that old 1985 Deines ZTR mower with a 5 ft cut.
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,855
Check out specification number 24539 and 24685. they are two of the M18 engines that were used on the deines mowers.
 

Rus A

Member
Joined
Oct 18, 2018
Threads
4
Messages
22
Check out specification number 24539 and 24685. they are two of the M18 engines that were used on the deines mowers.

O K I have a service manual exactly as shown in the one that is on this site. I ordered a new (aftermarket) ignition coil for this mower. Looks to be decent quality in its manufacture. Chinese I am sure. I put a dollar bill over the flywheel magnets and then tightened the new coil in place. mounted them this way for years. Put my new spark testers into the sparkplug boots and the other ends into the plugs which i laid onto the crankcase housing to ground them. I had already cleaned and lubed the starter twisted spline. Left the wire off the kill terminal. Shouldn't this new coil send spark to both plugs with no other wires attached to it? The engine is not in the mower, rather, it is on my workbench. I am still getting no spark. Engine being removed from the machine and all other wires disconnected I should not have to worry about a low oil indicator, right? After spinning it very well with a battery hooked directly to the starter terminals with no spark. I do have the heads off the cylinders thinking it should make no difference for testing. I then tested it as per instructions in the manual with my multi tester set on ohms. The old and new coil have virtually the same readings on the respective primary and secondary coils. Unless I am reading these wrong they both seem to read o k I will be taking them both to a small engine shop to have them take a look at 'em. BTW I still have not found any ID numbers on this engine. I figure they were stickers rather than stamped numbers or riveted on tags.
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,855
I know the model number tag was a sticker and is long gone. If the new coil is mounted with the correct side up (yes people put them on upside down), the mounting surface for the coil is clean and the wire is disconnected and the plugs are grounded well it should spark. Depending on type of spark tester you may not be able to get a spark through the tester and the plug, especially if the plugs are not mounted. Just too much resistance for the spark to jump the gap.
 

Rus A

Member
Joined
Oct 18, 2018
Threads
4
Messages
22
I know the model number tag was a sticker and is long gone. If the new coil is mounted with the correct side up (yes people put them on upside down), the mounting surface for the coil is clean and the wire is disconnected and the plugs are grounded well it should spark. Depending on type of spark tester you may not be able to get a spark through the tester and the plug, especially if the plugs are not mounted. Just too much resistance for the spark to jump the gap.

O K I will remove it and clean the mounting surface as well as the mounting surface for the bracket that holds it. Then I will clean a spot somewhere and lightly clamp the plugs to the engine somewhere. Plugs look fine but I will get new ones if that fails. If all else fails I will do the spark test like the old timers and hold onto the plug wires to see if they "bite me". I will retest both the old and new coils. Anxious to figure this thing out! Thanks for your guidance. My spark testers are new, but they are also chinese. I best check them on an engine I know has spark .
 

Rus A

Member
Joined
Oct 18, 2018
Threads
4
Messages
22
Eureka! I went to the shop and tried a few things. New plugs made no difference. Tried old timer test holding onto plugs. No shock. Hmmm. O K pulled off the coil and mount that holds it. cleaned all surfaces where these 2 parts mount back on. Took emery cloth to the mildly rusted surface where the flywheel magnets pass by the coil. After shining them up and cleaning the whole unit with a wire brush I polished the flywheel magnets also. I then recleaned the plugs that were in it when I bought it. One seemed slightly oily. Clamped them back to the block with the wires installed. Reinstalled everything & Hooked up the jumper cable to the starter and Voila! Beautiful spark from both plugs. Blue and strong. I was recently told that those rusty sufaces would not matter much. Guess I will ignore that tip. Anyway to finish cleaning crusted grease and spiderwebs out from the nooks and crannies, and remove cooked grease from the cylinder cooling fins. Looking forward to resurecting this old time mower to lasting as long as I want to drive one. I am expecting the need to clean out the carb after I cleared this hurdle. Thanks Ilengine for your help. I will keep you posted with my progress.
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,855
rust won't effect magnetic fields, but the rust will effect the grounding effect from the coil laminations to the engine block which can and will effect spark. Now with that said I have over the years cleaned the rust off of the flywheel magnet and would then have spark on the older briggs engines. People will argue that will have no effect, but I think the rust can and will effect the air gap between the coil and the flywheel preventing spark.
 

Rus A

Member
Joined
Oct 18, 2018
Threads
4
Messages
22
I cleaned and reinstalled one cylinder head and a new sparkplug. Hooked plug wire up and jumper cable to starter. Squirted a little gas but engine refused to fire at all. I put the other head back on, new plug & wire hooked up. With compression on both ends it spins a little faster with the starter. Small squirt of gas into each intake hole and each cylinder will now fire. More promising now. Intake manifold will go on next then clean the carb and put it on. I still want to pull the flywheel while this engine is on the bench. Maybe then it will run longer before it needs attention next time.
 
Top