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Repower 316 with 25hp Robin

9326 Views 38 Replies 13 Participants Last post by  koch140
So, if you're in this hobby long enough, friends and family all seem to know about it, and before long some of the "deals" out there have a way of finding you. I have had the good fortune of receiving a good number of these deals as my "informants" throughout the community let me know where they saw a JD garden tractor for sale, or who might have one they want to get rid of for nearly nothing.

That is how I came upon this 316, and actually how I got the deal on a couple of Robin/Subaru engines. The 316 had a bad engine and was given to me for the cost of going to pick it up from the local repair shop. I have had it in my possession for nearly a year and haven't touched it other than to move it out of the way from time to time.

The engine acquisition? Well, my father-in-law worked for a large manufacturing company that used Robin/Subaru engines in many of their products, and he had some very good purchasing power. He was able to get me this 25hp and a 28 hp fuel injected version for less than what I could have bought one of them from a normal vendor. I used the 28 hp fuelie to repower a John Deere 757 zero turn mower a couple of years ago. That thing had awesome power and seemed to run great, so I was always anxious to try the 25hp version out in one of the 318s I had when the time arose.

Well, I've been putting it off for nearly 5 years as the engine just sat there waiting, and this 316 wasn't doing any good sitting around with a bad engine, and with a local plow day coming up in less than two weeks, I thought it would be a fun project to see if I could complete knowing that I had a deadline of the plow day on October 11th.

Some items to note:
1. I do not ever plan to use the front PTO with this tractor. This is going to be a workhorse tractor for plowing, pulling a grader box, and spraying.
2. I want it done quick. I am not going to cut corners so to speak, but I'm not repainting or restoring here. I just want a functioning tractor as quickly as possible.
3. If this works out well, then I have a 318 with bad engine that I will likely swap this engine to. The 316 was convenient and in my way while the 318 candidate is buried in the back of a barn and has been somewhat of a parts donor the last couple of years. The 316 was primed and ready.
4. I have only seen one other Robin/Subaru transplant - and that was into a 420 which has more room inside the engine bay.

So, here is what I started with:

The tires have been holding air for nearly a year, which is a big plus when I chose my candidate!

Here is the engine that has been patiently waiting to find a new home for nearly 5 years:

Getting the old Onan out of there:

Trial fitting the engine. This engine sits much lower than the original, meaning the height of the crankshaft is closer to the ground. In order to use the front PTO with stock belts, I would need to raise the engine 1 3/8" off the factory mounting location. That puts the valve covers into the hood, so I settled for raising it only 3/4". I could probably still use the front PTO if I just found a different belt.
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Thanks so much for taking the time to help Andre! I was able to reference your remarks as I wired it up last night. You came up with a great way to clearly illustrate what needed to happen by drawing in color on that print! Awesome!

The only thing I didn't do was put in the relay as you suggest. One of Dan Dillner's wiring tutorials suggested that the ignition switch had two extra connectors that could be used to create a ground circuit for the coils when the key was off. I found this to be true, and used those connections on the key switch rather than install a relay.

I was able to get most everything done last night. I was excited to try it out, so after confirming the wiring with a voltage meter I plugged in the connections and hit the key. She cranked for about 5 seconds until I saw fuel in the filter, then I pulled the choke and VROOM, it came to life. What a relief to hear this engine run after sitting for so long. The engine was new in 2008 and never put in a tractor, so I'm just so happy that it fired up as easily as it did.

I ran it around in the driveway for a bit to see if anything obvious popped up. I had never driven this tractor either, so I was anxious to see what the hydro was like. To my surpise, the hydro seems incredibly fluid and responsive. It stops very well and holds still in the neutral position. Another relief for going into this blind! I then quickly installed the original heat shield around the muffler, then hooked up the throttle cable, put on all the sides, snapped some pics and called it a night.

The plow day is Saturday, and I'm thinking that I just might make it. Gotta switch out some tires and a 3 point hitch yet.

I have also put up a video of it starting and running on YouTube if anyone is interested to see or hear it run. The video makes it sound louder than what it really is in my opinion.

I can provide greater details on the install procedure, wiring, or whatever in the event someone needs them for a similar repower situation.

Now I'm looking forward to seeing how it does with a load behind it!
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Very nice install and tutorial. I believe that Robin/Subaru engine will perform nicely for you and last for many years. I am jealous of your fabrication skills and you do have a very nice shop.

Good Luck,

Bob P
Using the key switch to stop the motor will extend the delay of the safety like the seat switch because only the carb fuel cut solenoid will stop the motor.

Dan show the Vanguard original wiring on picture 32 but on picture 33 he show the connection with the tractor and he didn't bypass the safety.

Neil, Andre is correct you need to add the relay if you want to use the safety switches. The fuel shut off will eventually shut down the tractor but it is not safe. I recognized this after I repowered my initial tractor and added the relay in my documentation but as I just looked back I see my comments were not updated. I will update as I think it is important to have the tractor shut down when the safety circuit signals. Dan
On one repower on a skid steer with a Vanguard engine I used a relay and tied the common to the kill wire and the NC side of the relay to ground. The relay was powered when the key was on, key off relay no power and kill wire grounded.
All equipment is different but for our tractor using the key switch to feed the relay like you did is a bypass of the safety circuit.
Andre - Thanks for the follow up. I wasn't understanding it at first, but after reading it a couple times I finally get it! I didn't fully understand that I was bypassing the safety switches by leaving the coil "hot" when getting off the seat. Actually, the more I thought about it and looked into it, I am really only bypassing the seat switch really. I was concerned that I would be able to start it if the hydro lever was "in gear", but that feature is still enabled before the engine is running. Same thing with the PTO engagement. I just tried it, and the engine won't crank if the PTO is on or the hydro lever is engaged.
Ironically, this tractor doesn't even have a seat safety switch installed! (Not my doing! It was from the previous owner) So, at this point I suppose I'm not out too much. I will surely be looking into enabling all the safety switches at some point, as I have two little ones that I hope one day will begin to enjoy the hobby with me.

Dan - Thanks also for the feedback and the great Installation guide that you created for your installs. Your wiring diagram was my primary guide for getting things sorted out, as well as Andre's advice. I know what kind of time it takes to put something like that together, and myself as well as countless others appreciate your efforts in the great documentation. Kudos to you!

Tonight I am in the shop trying to get this tractor ready for a plow day. I have left it outside running at various RPM's for 30-45 minutes, just to see what kind of heat I'm getting under the hood and to make sure that everything stays running and nothing is vibrating loose. I'm probably crazy for just putting this thing together and taking it to a plow day, but I figure "what the heck!" If it weren't for the plow day for motivation, I probably would have pushed it aside for another "someday" project that never seems to happen. There are not enough Somedays during the week I have found!

Thanks for the comments guys.
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Also - John and Bob.
Thanks for the kind comments as well. I like the sound of it too, it certainly doesn't sound like an Onan, but it doesn't sound that intimidating either. It will be interesting to see if anyone at the plow day will notice that it is different than stock. I have tried to make it as discreet as possible, but the missing PTO clutch on the front is a bad giveaway.

Bob - Don't be too jealous of my fab skills! I rely on a grinder and paint to really finish off my welds.
The shop is new, and this is really my first project in here other than maintenance. I am still getting a feel for where I want my tools and how to organize things. The shop still isn't done, but I don't know if it ever truly will be. Funny, I have been planning this building in my head for nearly 20 years, and I still don't know what I want!

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Last night I put on all the plow day essentials: Bar tires and weight. These are some really old bar tires that have been in service for probably 30 years! I was using these same tires on a JD140 when I was a kid to plow our garden at home! They haven't been mounted to anything in roughly 4-5 years, so I thought I should give them a try.

I also borrowed some weights from one of my other tractors and mounted up a 3 pt hitch. I think I'm ready to get the plow down out of the barn and hook it up!



Now maybe I ought to think about washing it
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Might as well wait until you get back from plow day.
Yeah...I did say I was just thinking about it. I don't want to rush into anything
I'm more of a "function over form" kinda guy anyway.
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I'm not a good teacher but I'm happy, the problem is solved because you take the time to do a serious review.
Very interesting repower, nice fabrication and good luck at plow day.
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Neil, You did a real nice job tucking that new engine in the 316.
That is one heck of a plow tractor now!
Thanks for all the friendly comments gentlemen. I'm really happy with how it turned out and am hoping this engine type would be a good candidate for other repowers. They have a 28 hp fuel injected model that I think has the same physical size. I wish I still had another one of those to try!

We had a great time at the plow day and the engine performed really well. I was very pleased with the amount of power and by the sound when under load. I hope this engine proves to be a long lasting runner and I will get many years of service out of it.

Here are a couple pics of the 316 Robin at plow day, and below are a couple videos of it plowing.



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WOW, Looks like you and your gang had a good time. Now a good cleanup and you will be good to go.
We had a great time. I didnt even know this tractor was there. I would have liked to have seen it up close.
I already switched the tractor to sprayer mode and sprayed my yard with 2-4D on Sunday. I forgot to wash it again.

Matt, sorry you missed us. I saw you many times running around there with your 317. We were parked clear down by the end, second to last vehicle there on the northern most side.

The plow day was a great time as usual. I wished we would have had a chance to talk to more people too. I can never decide if I should sit around and talk or go plow. Since I had a new tractor we probably spent more time plowing
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