M18 Swap into CCC 782

[jpartak]

Ive searched and searched and i cant find the answer elsewhere so forgive me if i missed it. Im looking to buy a M18 off craigslist but i cant find cub spec numbers for the engine. Does anybody know what sec numbers kohler built for cubs, or can anybody tell me specifics to look for when i go look at the engine. Thus far ive only managed to come up with crank diameter of 1 1/8". Any other info or a link to a thread would be appreciated.

 

[jchamberlin]

James: The crank diameter is certainly a good start, it may be all you need. I have two M18s for my 782, the first one did NOT have the 1-1/8" crank, and it worked fine until I tried to install a Cub Cadet PTO. I had to change the adapter on the flywheel to accept the Cub Cadet drive cup, and I had to buy the exhaust elbows to fit the exhaust, but otherwise everything worked fine until I got to the PTO.

If you want to be sure the motor came from a Cub Cadet, look or ask about the exhaust elbows, or if the oil filler neck has a bend to it, or comes straight up: I've only seen the bend on Cub Cadet models. Those are two obvious ways to distinguish a Cub Cadet M18 from others. Also check to see if the PTO comes with the motor, because if you have to supply it, it is very expensive (although, if you have a PTO from a KT17 motor, it will probably fit). The correct PTO pulley has a diameter of about 4 inches.

Good luck, the M18 is a great motor as far as I'm concerned.

 

[rbedell]

James:

Here are the M18's Cub Cadet used...

 

[jstertz]

James--You are on the right track requesting the Cub spec numbers for the M18 motor. IMHO if that motor you are looking at doesn't have a Cub spec number, I would run away unless you want to lose a lot of sleep, weight, hair, etc

. If it is a Cub spec motor, the things that Jeremiah suggested will be in place but make sure you have the PTO situation in hand. If you have the old one from your KT motor and it is in good working order then you can install it. If not keep in mind what that will cost you. The exhaust elbows will be correct but keep in mind the electrical system will need some changes. Several guys on the forum have done this upgrade include Jeremiah and a good place to get you started is on the CCC page thread KT 17 series to M20 swap. Even though the M20 requires a different PTO and the M18 doesn't, you will find info if you follow the links to the electrical changes required when going from the coil type KT motor to the Magneto type Magnum motor. It is definitely a doable swap but being prepared is important.

 

[jpartak]

Thanks to all for the excellent information. With this guidance, at least I can make an informed decision. I appreciate all the help.

 

[nbextermueller]

I'm just going to hijack this thread for search function reasons...

So I finally got my Mag 20 into 782 swap finished and running. Using the wiring diagram from Roland and Steve B I was able to wire in the relay needed to ground the Mag and kill the engine. Here's the weird part... I took the relay and and 5 prong plug directly off an 1862 that had a spare Mag18 in it. But when I wired the Mag20 to the relay it had no spark. I took Steve B's advice and unplugged the Mag20 completely and it fired right up, meaning I had a ground issue.
It turns out, the 1862 had a prong in the wrong plug slot to work in the 782. It had a prong for 87 going to ground and left 87a unused. (Effectively reversing the desired affect) so I moved the wire over in the plug and now have a fully working 782 with a Mag20 and power steering to boot.

Here's where I'm interested in comments or a least hope to be helpful for future swaps. Be careful just swapping parts from new to old. Apparently the harnesses are wire opposite from one another. The only thing I can think of is the 1862 had power coming into the relay from the other side un-grounding terminal 87 so that it would run.

Anyways, hope it helps folks in the future. And thoughts or comments are welcome

 

[mgonitzke]

Were you using the PTO relay to run the ignition on the converted tractor? If so, the PTO relay on an 1862 doesn't perform the same function on that tractor as it does the way it is installed to use a magneto ignition on a tractor wired for battery ignition.

 

[nbextermueller]

Nope, this was the Mag relay. I took it right along with the 3 wire plug that goes to the Mag, oil, and reg.

So it didn't make any sense to me that it was backwards.

 

[mgonitzke]

There is no mag relay on an 1862; the only other relay is for the reverse cutout safety switch circuit, which has connections to the PTO switch, seat switch, and reverse switch. The magneto grounds directly through the ignition switch- no relay.

 

[nbextermueller]

Unfortunately I can't send you a picture because I already cut it out of the tractor. But the 3 wire plug coming off the left side of the engine that has the mag, oil pressure switch, and reg in it had 2 factory wires coming out of it going directly into 2 slots of the 5 prong plug directly attached to this relay. I'm not sure how to satisfy your argument...

I traced the mag wires directly from the engine to this plug and relay and simply cut them off the 1862 harness and wired it according the the diagram given to me from Steve B. this was clearly the relay intended to ground the Mag and stop the engine. It was wired to ground on the 1862 in factory tape. It apparently just had power coming into the opposite terminal than the 782 swap diagram indicates. Cause it was causing the switch to flip the wrong direction. Once I moved the plug, it worked perfectly.

 

[mgonitzke]

That does not match up with the factory wiring diagram for the 1862, in which the mag kill wire goes to the ignition switch and one of the two seat switches. It does not connect to the relay. The magneto is either grounded by the ignition switch (not the same type of ignition switch a 782 uses) or through the brake switch if the brake pedal isn't down when you get off the seat.

The relay is in the PTO switch circuit and turns it off if you get off the seat or back up. For this function, it is normally open, as indicated on the wiring diagram. This is opposite of what you want to use the M18 in a 782, where you want a normally closed switch to ground the mag with no power applied to the relay through the battery ignition switch, and the switch to open to allow the mag to function when the tractor's ignition is on. By moving the wire from terminal 87 to 87a, you convert it from a normally open switch to a normally closed switch.

Someone before you must have rearranged some things in the wiring of the 1862, probably trying to fix a problem with it. The wiring on those tractors was not good quality. The 1862 parts tractor I had was full of wiring mods.