Need advice/recommendation on repair/rebuild/replace Kohler KT735

[rbstern]

Our lawn cutter is an Ariens Zoom 54XL zero turn, purchase in 2015. The motor is a Kohler KT735. Been a reliable machine, except for a persistant oil leak from the head gaskets that I have never quite fully tamed.

During the last mowing session, the wife hit something, most likely a rock. She said the engine ran rough right after. She motored back to the shed and turned it off. I tested an hour later, started up okay, ran smoothly. I put it away. Today, she went to mow again, mower started and ran normally, but died after about 15 minutes. I checked the oil. Very low. I added oil, started it up, idled and powered up fine; no unusual noises and seemed to be running normally. Few minutes later, died again. And the oil was low again. Added a bit more oil, motor doesn't want to start, but will catch briefly at low rpm for a few seconds, blows fairly blue smoke and dies.

I have to assume a catastrophic internal failure, and the oil is going somewhere, either out the exhaust or somewhere onto the ground.

The shop I previously used for a mower engine repair has changed hands, don't know the new folks. I'm asking around on social media for recommendations for small engine repair shops. We'll see where that goes.

In the meantime, I'm also just considering a drop-in replacement for the Kohler. The mower is a good machine, has upraded transaxles, welded deck, and is in great shape, so it's worth repowering or repairing the motor. If Harbor Freight still sold the Predator vertical v-twin, I'd probably already be on the way to the store. But they don't seem to have them anymore.

Any comments on repair issues, or recommended potential replacement motors, would love to read 'em.

 

[Carl_NH]

I have 2 Kohler 18HP Magnum in Cub Cadet Garden tractor and the 25HP Kawasaki on my Ferris ZT and much prefer the Kawasaki.

The Kohler will run you $2200 range, and the commercial Kawasaki about the same Kawasaki Vertical Engine FX751V-FS00-S | Kawasaki Engine Store

IF you can rebuild yours that's the least cost, but if you need to pay to rebuild at $80-100/hour its probably better to drop in a brand new engine.

 

[rbstern]

Small engine guy came by yesterday AM, diagnosed the damage as a bent crankshaft and unknown amounts of internal damage. He had a very dim view of rebuilding (or repowering) with the same Kohler, says he's not a fan of their motors. Apprarently, leaking head gaskets is fairly common among Kohlers V-twin motors.

He also felt I could sell the Ariens as is, and it would be reasonable to start the asking at $1500, given that it is in excellent shape and has prosumer featuers (ZT-2800 transaxles, 10 gauge reinforced deck). That was his recommendation: Sell it and start over.

Problem is, to get the same level of parts quality I've got on the Ariens, I'm probably looking at $5000 or more for a new machine. For a machine that gets about 1 hour a week, about 30 weeks a year. That's hard to justify. One motivation would be to get a machine that has some sort of suspension, either seat or front casters; our terrain is bumpy and the ride quality sucks. I could put a suspension seat on the Ariens for a couple hundred bucks to solve this.

I can get a new Kohler Courage 24hp via ebay for about $1300. Most likely a drop in replacement that would take me a few hours to install.

I can get a better, new Briggs & Stratton 23hp commercial series for about $1000. Mostly a drop in replacement (same crankshaft dimensions), but will probably have to modify the muffler or buy a muffler for the new motor, plus may have some minor wiring challenges.

A Kawasaki would add another $600 or so to the purchase over the Briggs, but they have a different crankshaft size (both diameter and length), and that invites issues with the pulleys and electric clutch; I like their motors, but there's a limit to how much time I would be willing to spend on the repower work.

Also, I'm contemplating putting this off until mower sales season starts. Another 30 to 60 days? I can cut the grass with my brushcutter, although the wife will object to the rough cut. Or I can borrow a machine from a neighbor. Or go on craigslist or facebook and find a nearly used up rider for a few hundred bucks, that will cut a few more times in it's life. Hell, I could even do it with a cheapie push mower, if I had to.

Interested in any thoughts on this decision, particularly if you've repowered a zero turn.

 

[Richard001]

Small engine guy came by yesterday AM, diagnosed the damage as a bent crankshaft

Hard to imagine how a crank shaft would get bent on a zero turn.

Does this repair guy just happen to sell mowers ?

If it were me, I'd go with the Briggs & Stratton.

Richard

 

[oldnslo]

I agree with Richard not sure how you would bend the crank on zero turn. Another question, how would bent crank cause oil consumption? If it ran good with no vibration would be another indicator crank is not bent.

Did you check compression or look at the spark plugs? They should provide information on which cylinder is using oil.

Agree briggs is probably better choice if it fits and wiring isn’t to different.

 

[rbstern]

Recall this started with my wife hitting something, mostly likely a large rock. She probably hit the crankshaft itself. We had fiber installed on our street early this year, and discovered the trenchwork unearthed a lot of rocks, which can be hidden in the grass. We've already agreed the bush hog will be used to mow at the street from now on.

We started the mower, which will now only idle roughly for a few seconds, puffing blue smoke. The crank was clearly wobbling. The guy pointed it out, and I saw it with my own eyes. He's opinion was it was able to run normally for a few minutes before the imbalance tore something up inside, which is why it's now consuming large quantities of oil.

The guy doesn't sell mowers. He could have easily talked me into a rebuild and hundreds of dollars in labor for him. Instead, he told me to sell it and buy a new mower (which he doesn't sell). He's just a small-engine side-hustle guy, by all accounts, an honest one.

Two votes for Briggs. Thanks.

 

[5030]

Do not get a Kohler Courage. My wife has one on her ZTR and it's always been an oil burner since new and if the valves get slightly out of adjustment, it don't want to start (turn over). Briggs & Scrap'em or Kowalski for me. Cannot you tell, I follow Taryl's advice...

 

[Carl_NH]

Given the price delta Briggs to Kawasaki I vote the Briggs as it will last you at least 20-25 years with 30 Hrs/year.

Modifying the existing Kohler muffler or buying a Briggs muffler will set you back a $100 or so, but your under $1200 for a repower.

 

[workinonit]

My 2 cents that won't cost you a dime is that I would never own any other gas ZTR engine but a Kawasaki. I have 2 of them now plus a new Kubota diesel.

 

[5030]

Having both the Kohler Courage and the Kawasaki (on each of the ZTR's), I can tell you from actual experience the Kawasaki is a better engine, it don't burn oil and it starts easier. On the downside it's a pig on gas. The Kohler (both the same rated power, burns about 2/3rds the gas the Kawasaki does.

 

[tomplum]

I don't do a lot of engine swaps from one brand to the next. I have run into the need to switch out the exhaust pipes when I have though. If Ariens had offered like machines with a Briggs, those pipes may fit or maybe the muffler can be swapped. Oh joy, more expense.

 

[oldnslo]

Recall this started with my wife hitting something, mostly likely a large rock. She probably hit the crankshaft itself. We had fiber installed on our street early this year, and discovered the trenchwork unearthed a lot of rocks, which can be hidden in the grass. We've already agreed the bush hog will be used to mow at the street from now on.

We started the mower, which will now only idle roughly for a few seconds, puffing blue smoke. The crank was clearly wobbling. The guy pointed it out, and I saw it with my own eyes. He's opinion was it was able to run normally for a few minutes before the imbalance tore something up inside, which is why it's now consuming large quantities of oil.

The guy doesn't sell mowers. He could have easily talked me into a rebuild and hundreds of dollars in labor for him. Instead, he told me to sell it and buy a new mower (which he doesn't sell). He's just a small-engine side-hustle guy, by all accounts, an honest one.

Two votes for Briggs. Thanks.

My apologies for questioning crank being bent since on most zero turns I have seen it is up inside the frame rails and pretty well protected.

On engine change.
Where is oil filter and oil drain located on current engine vs replacement?
Where is carb and related linkage new vs old

Electrical. Do you wiring schematic for current vs replacement?

Engine changes can be full of the unthought of Surprises

 

[rbstern]

My apologies for questioning crank being bent since on most zero turns I have seen it is up inside the frame rails and pretty well protected.

On engine change.
Where is oil filter and oil drain located on current engine vs replacement?
Where is carb and related linkage new vs old

Electrical. Do you wiring schematic for current vs replacement?

Engine changes can be full of the unthought of Surprises

No apology necessary.

I have a 24hp B&S with matching muffler on the way. Expecting some minor wiring challenges. Will be eliminating the choke cable (new motor is single cable integrated throttle/choke), and I'll probably have to modify the rear frame to make clearance for the exhaust pipes. Verified with the seller's support staff (Small Engine Warehouse) the motor puts out enough amps to operate the electric PTO.

I'll spend some time this weekend removing the old motor and prepping the mower for the new powerplant. Will take some pics and post here.

 

[Richard001]

While removing the engine, take detailed photos of the wiring. Will come in handy later.

Richard

 

[rbstern]

Have all plugs and cables detached from the motor, the PTO clutch removed from the crankshaft, and the motor unbolted from the frame. Only thing keeping me from taking the bad motor off the frame is getting the pulley that drives the transmissions belt off. Not quite sure how to do it. The pulley is flush against the bottom of the motor, and their is a sleeve on the crankshaft below it, presumably holding it in place; I think the sleeve also acts a spacer between that pulley and the PTO clutch assembly. The sleeve has holes on opposite sides. Not sure if their is a fastener in the holes or some sort of thru pin.

Thoughts?

 

[tomplum]

I doubt that there is a fastener for this. Some manufactures are great about protecting the drive pulley w/ anti seize, others not. I assume that you've checked the IPL. Do you have a way to cut the crank above the whole mess so you can work at extracting the pulley?

 

[rbstern]

I doubt that there is a fastener for this. Some manufactures are great about protecting the drive pulley w/ anti seize, others not. I assume that you've checked the IPL. Do you have a way to cut the crank above the whole mess so you can work at extracting the pulley?

Yes, thanks for pointing it out. Just realized it's probably just stuck on the shaft. Will hit it with some penetrating lube in the AM, and then try to tap it off.

 

[mikester]

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Looks like $3,800 for a new disposable mower.

Toilet paper is also made to be used once and throw away. I think your first repair guy gave you good advise.

You got what you paid for...a throw away mower that will shake itself apart every 5 years. Manufacturers make this junk because people keep buying it. If you buy it at homedepot then its junk.

 

[rbstern]

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Looks like $3,800 for a new disposable mower.

Toilet paper is also made to be used once and throw away. I think your first repair guy gave you good advise.

You got what you paid for...a throw away mower that will shake itself apart every 5 years. Manufacturers make this junk because people keep buying it. If you buy it at homedepot then its junk.

Your comment is ignorant.

I'm in the process of taking this thing down for the motor swap. It's extremely well made. Everything about the machine is heavy duty. The paint is damn near perfect after seven years. None of the hardware is rusted. Haven't found any rust on the frame, either. Every electrical connector, spring, switch, and moving part I've put my hands on so far has been in 100% serviceable shape.

I can't defend the quality of the Kohler; the reputation is marginal and the perpetually leaky head gaskets never gave me confidence in the motor. But it's not the motor's fault it got whacked on the crankshaft with a large rock. It might well have given many more years of service without that event.

 

[rbstern]

I doubt that there is a fastener for this. Some manufactures are great about protecting the drive pulley w/ anti seize, others not. I assume that you've checked the IPL. Do you have a way to cut the crank above the whole mess so you can work at extracting the pulley?

That small hole turned out to be a place to tap on the key in the keyway. After some WD40 this morning, a few taps with a punch in that hole and the spacer and pulley fell right off the crank.

Thanks again!