F680 Kohler engine swap. How to save $$$$

[Kernopelli]

I have a f680 zero turn and the Kohler CH20 experience catastrophic engine failure. Broken camshaft, broken rod, broken piston, damaged crank, broken block. Pretty much destroyed the engine...a rebuild was out. JD and Kohler dealer wanted from $1600+ -$1800+ for a new Deere spec Kohler engine and I wasn't thrilled. A short block was $1200 w/shipping and I figured that would require a valve job just to do things right with the hours on the heads. I wanted to see if I could possibly swap a different Kohler engine into it, preferably one of the 22/23HP versions, basically converting the mower to a model F687. A little checking affirmed that the whole Kohler Ch18-22/23- CH 620-670/680 engines were built using the same basic major components but spec'ed differently for the manufacturers. Same blocks, heads, blower housings, basic muffler dimensions, etc. The main differences appeared to be some ignition options, which casting holes were tapped on the back case and crank diameter/ pto length. Since the F680 doesn't even use the crank shaft for pulleys or clutch mounting I wasn't concerned about it at all, as long as crank diameter was close for durability reasons. JD uses a 1" diameter PTO adapter that bolts to the flywheel and that's where the pulley and clutch mount...the engines crank/pto hang out the back and spin in the wind. A little searching revealed that all the kohler flywheels are all drilled and tapped for this pattern that accept the pto adapter. I also saw that the Kohlers are all wired with the same color coding system, the manufacturers may have a different plug connector but I figured you can cut the one off the old engine and splice it to the wiring on the new engine. My muffler would bolt right up so that wasn't an issue. motor mounts are the same. Idle and top speed revs were the same but that can always be played with a little if needed according to the kohler mechanics over on Lawnsite.com.I had a plan.

I found a Kohler dealer on eBay who was selling a bunch of new Kohler CH 670 engines for Cub Cadet tractors. They are rated at 22/23 HP, depending on what these engines are used in. I decided to take the plunge and ended up getting a brand new engine for a total of $604...retail is $1495 + $100 shipping. I'm feeling pretty good at this point but still don't know if my theory is all good yet. This might not work.....?

I got the motor and started bolting things together and all was right. I had to redrill some mounting brackets for the muffler shields, cut the old wiring connectors off the old motor and splice them to the new and everything else was a direct bolt in. The mower never ran better and I am tickled pink. Yeah, it's not "original JD" anymore but I have 10%+ more power, a new factory engine ( and warranty) and saved over $1000.:thumbsup: I could not be more pleased. Same Kohler quality and this mower didn't run this good off the show room floor! I really lucked out with the way JD does the bolt on PTO, it makes matching up cranks less critical but even if I had to deal with getting an engine with the same crank length, there are a lot of options and price differences in the Kohler line and between the manufacturers that use them......and I am now convinced, it really doesn't make much difference when there is so much similarity between so many of their engines. If you are the type that doesn't mind messing with things a little bit and doesn't care if it's no longer factory original ( like my 10 year old JD mower w/ new Cub Cadet engine), a guy can save a lot of money by looking outside the box on these Kohler engines. BTW: The Kohler website is a wealth of information for cross referencing things.

 

[Kyle_in_Tex]

good post, glad u saved big $$$

 

[jenkinsph]

Agree, good post:thumbsup:

Glad you found an economical resolution.

 

[braymer]

I think I may have upped the ante a bit on my f680 engine swap. In looking around for a deal on the similar Cub Cadet, I found that the Kawasaki V-twin engine series was even more appealling. Other than the wiring harness having to be adapted and some modifications to the headers and some creativity in how we ran the high capacity air cleaner, the complete 770d engine fit like a glove and we have gained twice as much torque and are running the engine at 80% under full load in extremely thick oklahoma TU419 bermuda! For those that don't know any different, this is the fine blade bermuda that is normally maintained as putting greens and cut with a reel mower. I'll post some pics later but I can tell you that a smaller drive pulley and some flames on the hood now have this bad boy being loaded on a trailer and used at local shows for the resident Deere dealers.

 

[Kyle_in_Tex]

I think I may have upped the ante a bit on my f680 engine swap. In looking around for a deal on the similar Cub Cadet, I found that the Kawasaki V-twin engine series was even more appealling. Other than the wiring harness having to be adapted and some modifications to the headers and some creativity in how we ran the high capacity air cleaner, the complete 770d engine fit like a glove and we have gained twice as much torque and are running the engine at 80% under full load in extremely thick oklahoma TU419 bermuda! For those that don't know any different, this is the fine blade bermuda that is normally maintained as putting greens and cut with a reel mower. I'll post some pics later but I can tell you that a smaller drive pulley and some flames on the hood now have this bad boy being loaded on a trailer and used at local shows for the resident Deere dealers.

Would like to see pics of that!