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Installing Onan 18hp from a 318 in my 316

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#1 Tonyp884 OFFLINE  

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Posted June 24, 2015 - 07:16 PM

Hello guys, I am new to this forum.

 I have a really nice JD 316 with an Onan 16 twin that is worn out. One cylinder is very low compression about 80 if I remember and the other side is about 95. The motor uses a lot of oil. I am the 3rd owner and have been using the 316 a lot. I ran across a heavily used 318 that has an almost new Onan Performer 18 by Linamar repower engine in it. The 318 runs great! I want to put the 18 hp engine in my 316. But the biggest thing I see so far is that the 18hp engine has a different starter and the 318 frame has a cutout for the starter that my 316 frame does not have.I do not know of any other differences. A friend said that I should be about to get a "different" starter for the Onan Linamar 18hp so that it would fit into my 316 frame. Can you guys help me out with this?

Also, I would like to find a service manual and wiring diagrams.

Any times suggestions before I start removing and swaping these engines would be greatly appreciated!

thanks ahead of time!

Tony P

Monroe, NC

#2 dropped82 OFFLINE  


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Posted June 24, 2015 - 07:22 PM

IIRC, you'll have to swap oil pans to change the starter. I had the same thing when I was working on my 420 using some older engine as parts.

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#3 Alc ONLINE  



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Posted June 24, 2015 - 08:38 PM

Welcome to GTTalk ! Not sure what the frame looks like on your 316 but when I repowered my 318 with a newer motor I ran into the starter problem I believe your talking about , I cut 2 slits in the frame and bent the metal away for clearance . My thought was to weld reinforcments but never did Hasn't affected it but again I don't know the 316's frame
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#4 dodge trucker ONLINE  

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Posted June 24, 2015 - 10:20 PM

what else is wrong with the 318? just run that one instead and don't worry about swapping/

#5 JDBrian OFFLINE  


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Posted June 25, 2015 - 05:01 AM

If you can get a good look at the 318 frame you can determine if there are any other differences. I would consider taking some pictures and just duplicating the cutout on the 316 frame. There may be other differences with motor mounts and bracing to consider.

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#6 Tonyp884 OFFLINE  

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Posted June 25, 2015 - 07:00 AM

The 318 was used for Years at a landscape company with a bucket on the front. The steering is so loose it is almost not driveable. The wiring is horrible, no guages or lights work, with a push button starter. And appears to be missing some brackets missing underneath.  And it is just plain ugly and DIRTY. But, the motor is almost new and runs great! I guess I could try to fix the steering looseness and transfer all nice 316 parts to the 318.

Still need a wiring diagram and service manual. Read a lot of posts on here last night, lots of good info here !


Tony p

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#7 hdg4400 ONLINE  



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Posted June 25, 2015 - 08:27 AM



Welcome to GTTalk. Lots of members here (not necessarily including me) who are very knowledgeable about Garden Tractors. I have a 318, and  I love it, especially the power steering.


Check your personal messages. I have some info that might be of use to you.