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John Deere 400
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Discussion Starter · #1 ·
I finally decided to repower my JD400.
The “back story”:
I bought this machine probably 10 or 12 years ago. I hadn’t done any research and didn’t really care what condition it was in because I was convinced that I could fix anything and would have it tip top in no time. Didn’t happen. Just too many other projects to work on. The 400 got only the attention it needed to make it do what I wanted it to do.
I don’t remember what happened to the first K532, but I was in a hurry so I just threw an engine together with whatever parts I had laying around and put it back to work. The replacement leaked/burned oil so bad that it lost oil pressure while my wife was mowing and broke a rod. It was my fault, I told her she did not need to check the oil. At that point I used a K582 block and built a hot rod engine for it:
  • I had it bored as large as I thought I could get away with.
  • Offset ground the crank for additional stroke.
  • Used Kohler 10HP rods that were machined to accept bearings at the big end.
  • Custom JE pistons to work with the longer stroke and longer rods.
  • Bumped compression.
  • Thermal barrier coatings on the pistons, heads, valve faces, exhaust ports, and block face.
  • Larger intake and exhaust valves with a lot of port smoothing in the block.
The hot rod engine ran great. I could mow in high range at full speed without lugging the engine. But I noticed at the end of last season, the power was down. It still seemed to start and idle fine, but was no longer able to hold the load while mowing, especially uphill.
When I started it a couple of weeks ago it had a bad knock and before I could investigate the source, it stalled abruptly.
With about 130 hours on the hot rod engine, the crankshaft snapped and allowed the flywheel to get into the stator and oil cooler. During teardown I also found both exhaust valves were in pretty rough shape which would explain the low power.

The Direction:
I had originally thought about throwing another K532/K582 together with whatever parts I have laying around. Then I thought of just buying a much newer zero turn. But I ultimately decided to repower. Going cheap with a Predator was the first route I looked at, but I just wasn’t comfortable going through the effort to repower with an engine that may not live. I was amazed to find that the Honda GX690’s can be had for under $1500 from small engine warehouse. I’ve been a fan of the Honda small engines for years and just expected them to be more expensive than that. I ordered one up on Friday and it was delivered yesterday (Monday).
I’ve looked around for other threads showing Honda repowers and I find lots of reference to them, but I’m not able to find anything with any photos. I thought I might as well document this with some photos for the next guy looking to go this route. BTW: If you know of any threads that still have photos feel free to link them here! Would be nice to see what others have come up with.
I know there are repower kits available, but I thought they were priced pretty high compared to just the engine. I should be able to fabricate most of what I need. Depending on how this goes, I may change my opinion on the price of the repower kits by the time I’m done.
At any rate, here are the first few photos from the project:
The broken K582 crankshaft.
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The Honda after unboxing.
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The engine compartment after a little blast from the pressure washer.
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Test fitting the crank pulley.
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And the engine set in front of the machine to start to visualize.
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Takes me back to the good old days. (Your hopping up the engine) I've seen a couple of crankshafts similar to yours but coning out of a race engines.

The Honda would be my choice also. And I would go the same route you're taking in fitting it myself. I did a similar install in my 317 by installing a Kohler Command 20. It was likely a bit easier as the major dimensions were very close to the KT I removed. I chose the Command only because I picked it up cheap. I paid $100 bucks and so far so good with about 200 hrs. since the install. It runs OK. A bit differently with almost every startup. I did it just for a pass time and a lot of other unusual things while I was at it.

But it was my intentions to keep the tractor looking like a 317 not something which has been hacked and easily seen from the street. I accomplished that. The exhaust being the hardest. I also made a particular effort to keep the original isolation mounts which I would encourage you to do also if at all possible. I fabricated my own driveshaft using much heavier u-joints. It required a small amount of relieving around some frame areas but nothing serious. Again, I would recommend you look into doing something similar if your shaft looks worn or requires a lot of modification anyway.

As I really don't have a lot of confidence in the Command engine I'll be looking forward to watching your progress. There is no question in my mind that if I spend the money for a new engine it will be a Honda. And my next machine will be a 400. When I find one.

It looks good so far.
 
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John Deere 400
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Discussion Starter · #4 · (Edited)
I also made a particular effort to keep the original isolation mounts which I would encourage you to do also if at all possible.
I absolutely intend to keep the original isolation mounts. Probably going to cut up the original mounts from the Kohler and use them to fab new to fit the Honda.
I fabricated my own driveshaft using much heavier u-joints. It required a small amount of relieving around some frame areas but nothing serious. Again, I would recommend you look into doing something similar if your shaft looks worn or requires a lot of modification anyway.
Driveshaft is up in the air yet depending on the placement of the engine and the required length of the shaft. I JUST rebuilt this driveshaft a month or so ago with all new bearings and hardened drill rod for the pins. I'm hoping I can use it as is, but I'm not going to compromise to make that happen.
 

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You've gone the extra mile to keep that 400 original but if you need a reliable worker the repower you're doing with a modern new engine is a pretty good idea, IMO anyway. Expect much better fuel mileage too. My VG's are consistently using less than half the gas my K532's do. The Honda should do that too. You're also gonna love it for other reasons, like the extra wheaties.

I have 23 HP Vanguards, one in a 400 and one in a 420 but my brother has a 420 with a 24 HP Honda. The original Onan was replaced with the Honda by a JD dealer and was documented. The 420 itself had a couple thousand hours on the clock at the time and it has over 5000 hours now. It was maintained by the dealer after the engine swap and the documentation indicates nothing major has been done to the Honda since the install. So there's about 3000 hours on it and it's still starting and running good. No smoke and or oil usage at all. He replaced the carb but that was due to it being gummed up pretty bad from sitting with gas in it for several years before he bought it from the JD dealer where it was repowered.

There was an alleged overheating issue with the Honda repowers years ago and the word on various forums was avoid them and go with a VG engine. But I never saw one valid documented test on a Honda to prove it was true. It was just hearsay and was around the time SEW switched to VG's for their repower kits. Not saying there was any disinformation about the Honda's in the forums. Not saying there wasn't either.
 

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There was an alleged overheating issue with the Honda repowers years ago and the word on various forums was avoid them and go with a VG engine. But I never saw one valid documented test on a Honda to prove it was true. It was just hearsay and was around the time SEW switched to VG's for their repower kits. Not saying there was any disinformation about the Honda's in the forums. Not saying there wasn't either.
My attitude toward anything foreign is usually negative but Honda engines are the exception. They taught, if not forced the others to do better. My short stint repairing tools at the Fort Myers HD really convinced me. They were nearly exclusive Honda back then and those engine went through more abuse than any owner could put on in a lifetime. I bought a pressure washer from the rental which had according to the computer well over a thousand rentals and an estimated three thousand hours accumulated. I think that was a conservative guess as those machines usually run about four hours on a tank of gas and they always came back empty. On mine, the pump died but that engine is still perking along strong. And to this day, at least ten years later, it still starts with a single pull of the rope. Every time!

As for "disinformation" and "hearsay" on these sites? About the same as Facebook in my humble opinion. Especially hearsay!
 
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Discussion Starter · #7 ·
It looks like today my phone may play the fun game of putting every picture in sideways regardless of how I rotate them. Sorry about that.
I pulled the fan screen off to see what I had to adapt to at the fan end. The holes are m8x1.25. I have these socket heads that fit, but I might need something longer depending on what I work out.
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I set the engine in place on a couple boards to get an idea how it will fit.
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The hood and side shields were loosely installed to check clearance. The only problem I found was the PTO cable guide hits the oil fill cap, so that will require some rework.
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I am interested in the exhaust.

Does any exhaust come on the engine? How easy to modify, if so?

Could you post some pics, when You can.

winky
 

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Discussion Starter · #9 ·
I am interested in the exhaust.

Does any exhaust come on the engine? How easy to modify, if so?

Could you post some pics, when You can.

winky
There were several versions of this engine to choose from. Some came with exhaust, some had different crank (PTO) sizes, one had a Donaldson air filter, etc. I ordered with no exhaust. I’ll be fabricating my own. I thought the additional cost for a muffler that may not fit well was too high.
Here’s a shot showing the taped exhaust ports.
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Discussion Starter · #10 ·
I started comparing the PTO end. The Honda shaft is roughly 1.5” longer than the Kohler.
Honda:
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Kohler:
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Shouldn’t be a problem, I’ll just slide the pulley on as far as necessary and make up spacers to locate it. But, the pulley would not slide all of the way onto the Honda crank due to a slight ridge at the outside edge of the bore. The ridge was very slight and it isn’t supposed to be there, so a few minutes with a rat tail took care of that:
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Loosely Installed:
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Probably not going to get much done tonight. Other plans.
 

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I too will be curious to see what you come up with for an exhaust system. I love the 'bundle of snakes' exhaust system that race car teams, mostly formula cars, come up with, sheer beauty! Your little 2-cyl should not be quite so complex, I know they like to keep their header tubes the same length in the race car motors.
 

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Discussion Starter · #12 ·
I too will be curious to see what you come up with for an exhaust system. I love the 'bundle of snakes' exhaust system that race car teams, mostly formula cars, come up with, sheer beauty! Your little 2-cyl should not be quite so complex, I know they like to keep their header tubes the same length in the race car motors.
I don’t plan to get too fancy. There just isn’t much room. I considered twin strait pipes. One coming out each side, but I just don’t like the noise.
I’ve also considered an expansion chamber followed up by a muffler, but I don’t think that makes sense either. There isn’t enough space for proper length head pipes so that an expansion chamber can work properly.
 

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Definitely leave extra crankshaft till you come up with a final resting place for the repower. You may end up moving back on tractor to couple driveshaft and gain room for exhaust in the front.
 

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....There was an alleged overheating issue with the Honda repowers years ago and the word on various forums was avoid them and go with a VG engine. But I never saw one valid documented test on a Honda to prove it was true. It was just hearsay and was around the time SEW switched to VG's for their repower kits. Not saying there was any disinformation about the Honda's in the forums. Not saying there wasn't either.
I recall those reports as well. However, T.H.E and repower specialists still offer gx630 kits for about $400 more than the sew Briggs kits ($2100). The former company I believe is a Deere dealer and used to participate here. The latter has had some negative feedback about the company, but not related to the Honda.

Dropped an intake seat on the 318 recently and have been pondering the direction I want to go. Glad I was paying a little attention to these discussions over the years. 😄
 

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I put an original Honda muffler on my GX670 when I did my home made repower for my 318.
Some details of the modifications here...
 

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Re-powers are one of my favourite threads here. A reliable new engine is a game changer. Dealing with everything else on a tractor is worth the time and effort if it has a stout heart. The 23 HP Vanguard on my 420 works like a champ. Sounds like one too. I've never had an Onan but I can't imagine they're better than that VG (so far anyway). The VG on my 400 seems every bit as good. I like Honda engines just as much and maybe more. I see acre after acre of satisfied smiles with yours.

I even painted the flywheel shrouds JD green so they'd look at home in my tractors. Possibly the easiest prep and paint jobs I've ever done. Just remove the shroud and lightly sand it, tape off the decal/spec tag, shoot the green on and presto.
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Re-powers are one of my favourite threads here. A reliable new engine is a game changer. Dealing with everything else on a tractor is worth the time and effort if it has a stout heart. The 23 HP Vanguard on my 420 works like a champ. Sounds like one too. I've never had an Onan but I can't imagine they're better than that VG (so far anyway). The VG on my 400 seems every bit as good. I like Honda engines just as much and maybe more. I see acre after acre of satisfied smiles with yours.

I even painted the flywheel shrouds JD green so they'd look at home in my tractors. Possibly the easiest prep and paint jobs I've ever done. Just remove the shroud and lightly sand it, tape off the decal/spec tag, shoot the green on and presto.
View attachment 267202
GREAT touch! Looks really sharp
 

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army said:
....There was an alleged overheating issue with the Honda repowers years ago and the word on various forums was avoid them and go with a VG engine. But I never saw one valid documented test on a Honda to prove it was true.

Agree - I mow in 90+ degree heat all summer. It's a 46" mower, but is also driving a PowerFlow.
All covers in place, no overheating issues in 8 years.
 

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When/if you have time check out what the golf cart guys do with the Hondas and Vanguard motors, including the exhaust..


I don’t plan to get too fancy. There just isn’t much room. I considered twin strait pipes. One coming out each side, but I just don’t like the noise.
I’ve also considered an expansion chamber followed up by a muffler, but I don’t think that makes sense either. There isn’t enough space for proper length head pipes so that an expansion chamber can work properly.
 
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