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Repower 316 with 25hp Robin

9329 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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The Robin engine has a spin on filter and oil cooler that are going to interfere with the left side of the frame and side shields, so I had to do a little cutting in order to accommodate the protruding components of the new engine:

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After some measuring, cutting, mocking, and recutting, I was able to get the engine to sit in there with both side shields and hood closed. I had to remove the fuel pump from the left side of the engine which I will relocate to somewhere out of the way.

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Here you can see the fuel pump that needs to be moved as it will hit the side shield:

The right hand side provided much more clearance:

So far, I have only been using wood to raise the engine, so the next step will be to build a engine mount setup to raise it up the 3/4" I need. I'm doing things on the quick here, so I'll be using some 1/4" plate I had laying around stacked on top of some 1/2" plate. Here is the start, and I can hopefully finish the engine mount up tonight.

I ordered a muffler that will hopefully be here before week's end, but I fear that I will need to modify it a bit in order for it to fit. Once I get the engine mounted, I will need to work out the muffler, the drive shaft adapter for the flywheel side of the engine, and then finally the electrical side. I have started this thread in an effort to keep me motivated to finish it up and also to see if anyone had any suggestions on the flywheel adapter I will need to get. I was hoping that perhaps one of the Honda adapters from SEW might work. My next step is to do some research into that aspect of the swap. We'll see what tonight brings!
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Thanks for the feedback guys!
My flywheel has four holes, but the spacing is larger than the four holes on the driveshaft flange.
I bought a Briggs adapter from SEW. I have no idea if it is going to fit or not. I tried to do some research and find out if the spacing was the same between the Briggs holes and the Robin holes. Chances are, it will not work and I may need to go a different route, and I will just return the adapter if that is the case.

Last night I made up a riser plate to raise the engine 3/4" from the factory mounting location. I drilled and tapped the holes so that it could be bolted on from the bottom, and then the new engine will be bolted to the plate from above. This way, I can have the engine mounted, and then set it in the frame and secure it from the bottom, which I think will make it much easier to install or remove in the future.

I think that the muffler will show up today, and the flywheel adapter either today or tomorrow. I will have a couple evenings of fabrication I believe to get the muffler stuffed in there. If the flywheel adapter doesn't work, then I have a neighbor with a lathe that might be able to help me make one from scratch.

I like your idea Andre, and it may come to that in the end. I would need to order the stub shaft from Subaru, which I did on the last repower that I completed for the JD 757.

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Dennis - It could be a Kohler adapter, and maybe that would have been a better choice. Honestly, I was having trouble finding any info or cross referencing capabilities to see what already exists that might work. I'm sure it is out there and available, I just didn't put the time in to find it.

Roger - I haven't found the Subaru adapter that you are referencing. I did find a stub shaft that bolts to the flywheel that would provide a 1" shaft, but then I would need to modify the u-joint on the end of the driveshaft. Is the stub shaft what you are referencing? Or is there something else I have overlooked? I looked through the accessories catalog and only see the stub shaft for the flywheel side.

At the top of Page 2 on that link is the shaft adapter.

Thanks for the tips guys.
Well, a bit of a set back at the moment. The drive shaft adapter that I ordered from SEW doesn't fit. The guy on the phone that I talked to (on the 3rd call) told me that he thought it would fit. The hole spacing on the Briggs adapter crankshaft side is 2" between holes. My holes on this Robin engine are 2.09". It is close, but just won't work without serious modification. I would also like for the adapter to be about 3" long, whereas the Briggs adapter is 2.75". Does anyone know off the top of their head if the Kohler adapter might work? I will attempt to do some more research but I suppose if someone knows right off the bat it could help. I am currently working on the muffler and will hopefully have everything ready for when I find the right adapter or do as Roger suggested, and just go with the 1" stub shaft with modified U-joint setup.
I couldn't find an flywheel adapter/spacer for any other application that would suit my needs here. I actually called SEW to ask if they had anything that might work and the guy on the phone informed me that they don't sell flywheel adapters that aren't part of a kit. I laughed and told him I was currently holding one in my hand that I had ordered from them last week! Apparently the parts guy wasn't aware of what parts they actually sell!

Anyway, I thought about the stub shaft idea, but learned that the 1" stub shaft adapter from Robin/Subaru was $115, plus I would need to rebuild the drive shaft. That sounded kinda spendy, so I decided just to modify the adapter I originally purchased to make it work. Fortunately my neighbor is a retired machinist and has an awesome home shop and was able to accomplish this for me, and I will pick up the adapter this evening.

Over the weekend I made up some exhaust tubes to fit the stock Onan muffler. Hopefully it isn't too restrictive. Tonight I plan to trial fit the engine again and hopefully start working on the wiring.

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Thanks Mike. Welding up the exhaust was certainly an exercise in patience!

I stopped by the neighbors to pick up the modified flywheel adapter. It fits and works just fine and I don't think I will have a problem with it. I am lucky to have someone so close that is able to accurately modify parts like this!

He had to drill a second set of holes at the proper spacing and also bore in a recess on the back side to center and clear the step at the end of the crankshaft.

Engine mounted and adapter sticking through the flywheel housing.

I shot a little black high temp paint on the muffler and exhaust tubes and got it mounted up. I think it looks OK for a quick fab job using the stock muffler.

I moved the fuel pump to the firewall. I'm not sure how this is going to work out. I ordered some firewall insulation from John Lang today because I fear this setup will get too hot, and I will need possibly move the fuel pump or make some revisions to keep it all in there like I have it.

And, I am still working on the wiring. I think I have it figured out based on some research here and a very nice tutorial by Dan Dillner. I would be interested though, to ask if anyone has any comments on this part of the install. Here is the wiring diagram that came with the engine. Is anyone able to just look at this and know for certain which wires of the JD harness need to go where?

This 316 had a B43 Onan in it, and as a result has the starter solenoid under the battery tray. Here is my thinking on what JD wires need to go to the Robin Engine:
Purple wire from JD solenoid >>> Red wire to starter
Pink wire in JD 3 pin connector >>> Red/Yellow wires to Carb and Oil Lamp
Green wire in JD 3 pin connector >>> Yellow Wire going to starter post, then on to regulator.
Stop circuit posts of JD ignition switch >>> Go to Black/White wires to coil packs on Robin (I will need to populate the two non-used posts of the ignition switch which are available to supply ground to the coils to shut them off)

The only thing really holding me up is that the Robin yellow wire is tied in with the red carburetor wire. I have the tan wire of the JD 3 pin connector left over it seems.

Thanks for any insight.

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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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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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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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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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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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