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Repower 316 with 25hp Robin

9325 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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It's another great homemade repower project and this is very interesting to follow with all those nice pictures.

For my own 318 homemade repower with a Honda GX670, I bought the adaptor from Honda and a U joint from Weasler.

I choose this solution because for me it was possible to move the U joint to reach the stock driveshaft.
Also with this setup the cooling air supply is larger than with the huge SEW adaptor.

This adaptor is easy to fabricate and probably cheaper than any original and maybe it can be adapted for your stock driveshaft and the U joint was less than $20.00.

Great job, thanks to share!
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Everything is ok with the following exceptions...

Forget the Yellow to the Oil lamp the actual wiring take care of this side of the lamp.
For the other side connect the pressure switch Gray with the Tan of the 3 pins connector.

For the carb solenoid, connect the Pink of the 3 pins connector with the Red/Yellow like you said.
Use the Yellow to feed a 12v relay with a NC contact and follow the drawing.

The carb solenoid can be use to stop the engine but it will stop only after a long delay when gas is missing.
For this reason you have to use the Black of the coil with the safety circuit to stop the engine immediately like the Onan.

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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.

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.
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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