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Discussion Starter #1
I went halves on this tractor about a year ago with my brother in law. He wanted a plow for his 322 and I got the tractor and 50” deck for 925 bucks. I tried to look for all the things I could when inspecting it and I could tell that there was probably an oil leak somewhere. When it started up it sounded ok and the throttle seemed pretty responsive. What did I know? Besides my brother in laws 322 this was the first 318 I ever saw let alone heard. So we did the deal!
It wasn’t Long before the problems started.
1. Seems to have an oil leak coming from the front crank seal? Behind the PTO.

2. In the 1.5 hrs or so it takes to cut the lawn, it will randomly just shut down. Wait 5 secs and it will start up. From what I’ve seen could this be the ICM?

3. One of the ears on the oil pan is broke.

4. And finally it started running rough. So I checked the compression and it was low on the right side. Adjusted the valves and 4 time serts later I had good compression in both sides. Seemed to run ok after that, but I started to see oil in the air cleaner.

So I have it in the shop now, tables are cleared, tools are all put away and ready to get down to business. Figured I would just do a quick compression test before I posted this and now I’m only getting like 50 psi on the right side. So I guess that would that explain the oil in the air cleaner?

My thoughts are new ICM, used oil pan on eBay and put new rings in. Is the crank seal hard to replace? I would rather stick with the onan than repower with something else. Also trying to not go crazy $$$$$

Make no mistake, I thought this thing was running pretty good when it actually wasn’t. I would really like to see what it’s got with good compression! Any suggestions or advice is appreciated.

Thanks
 

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Kish JD 318/420/430
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The main mistake with the Onan that a lot of people make. They think rings only but this is a horizontal piston engine and so the cylinder wear in an egg shape. They just throw rings at it and within in a few hours of operation your back to the same old problem. So you have to measure the bore on both cylinders and be prepared for a bore job and moving up in piston size and rings.
 

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Discussion Starter #3
The main mistake with the Onan that a lot of people make. They think rings only but this is a horizontal piston engine and so the cylinder wear in an egg shape. They just throw rings at it and within in a few hours of operation your back to the same old problem. So you have to measure the bore on both cylinders and be prepared for a bore job and moving up in piston size and rings.
I see.... makes sense. Thanks Russ
 

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USMC Ret. / JD 318 owner
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198 Posts
FWIW, If the timing plastic ring with magnets in it that sits behind the flywheel is not aligned with the timing sensor as it can be pushed back too far, the engine will run for about an hour and then just give up until it cools off. My first 318 had this problem that the previous owner didn’t disclose to me, but I finally figured it out since it was obviously an electrical issue. I noticed that the quality of the spark was nil when the engine heated up, but was great once the ring was aligned.


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AKA Moses Lawnagan
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FWIW, that's a 1987 model given the SN you show, and that should be a P218 engine. 1987 was a change-over year for engines. Prior to 420xxx SN, it was the B43G so yours is an early P218 motor.
 

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You got a very good deal on a very clean looking tractor. As RussKish pointed out, this isn't a simple ring job, plus whatever other engine control problems you may or may not have.

I honestly don't know why you don't want to consider a repower, but that's your choice.

Another FWIW, is that an acquaintance bought his 318 new in 1985. The B43G died after 2 years. He had a shop upgrade it to a brand new P218G. Since then, it's had yet another brand new Linamar. He still uses it, but has only around 2,500 hours (total machine time) the last time he and I had a tractor talk. Obviously he takes good enough care of stuff to get 34 years out of it, but I guess my point is that Onans aren't bullet proof, and a Honda is a pretty darn good engine.
 

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The front seal is not a big deal to replace. If you already have the PTO off then it is just a matter of pulling the old seal and putting in the new one. I use a sheet metal screw with a big head on it to remove these seals. Drill a small hole in the sheet metal part of the seal and then screw the sheet metal screw into it a small amount and then pull on the screw head. I usually use two screws, one on each side of the seal so that I can pull alternately until it comes out. I had a JD 400 with the Honda in it and it was a dream compared to an Onan or old Kohler. If you are thinking of keeping the 318 long term, I would suggest looking at the Honda real carefully before putting a lot of money into that Onan.
 

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Discussion Starter #8 (Edited)
FWIW, If the timing plastic ring with magnets in it that sits behind the flywheel is not aligned with the timing sensor as it can be pushed back too far, the engine will run for about an hour and then just give up until it cools off. My first 318 had this problem that the previous owner didn’t disclose to me, but I finally figured it out since it was obviously an electrical issue. I noticed that the quality of the spark was nil when the engine heated up, but was great once the ring was aligned.


Sent from my iPhone using Tapatalk
Thanks, that's good stuff to know. It seems there was a lot that wasn't disclosed to me either.

FWIW, that's a 1987 model given the SN you show, and that should be a P218 engine. 1987 was a change-over year for engines. Prior to 420xxx SN, it was the B43G so yours is an early P218 motor.
Thanks for the info.

You got a very good deal on a very clean looking tractor. As RussKish pointed out, this isn't a simple ring job, plus whatever other engine control problems you may or may not have.

I honestly don't know why you don't want to consider a repower, but that's your choice.

Another FWIW, is that an acquaintance bought his 318 new in 1985. The B43G died after 2 years. He had a shop upgrade it to a brand new P218G. Since then, it's had yet another brand new Linamar. He still uses it, but has only around 2,500 hours (total machine time) the last time he and I had a tractor talk. Obviously he takes good enough care of stuff to get 34 years out of it, but I guess my point is that Onans aren't bullet proof, and a Honda is a pretty darn good engine.
Thanks for your advice bufordT. When I posted this I was afraid that my plan may not be the best. Honestly, repower is not off the table. I'm really not sure what I am gonna do yet. I ended up working all weekend and a graduation party, so I didn't have time to work on anything. I am gonna just double check the valves one more time just to see if something happened there.

The front seal is not a big deal to replace. If you already have the PTO off then it is just a matter of pulling the old seal and putting in the new one. I use a sheet metal screw with a big head on it to remove these seals. Drill a small hole in the sheet metal part of the seal and then screw the sheet metal screw into it a small amount and then pull on the screw head. I usually use two screws, one on each side of the seal so that I can pull alternately until it comes out. I had a JD 400 with the Honda in it and it was a dream compared to an Onan or old Kohler. If you are thinking of keeping the 318 long term, I would suggest looking at the Honda real carefully before putting a lot of money into that Onan.
Thanks rudy, I thought I saw that you had done this some where before. Your the man! :thThumbsU
 

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Discussion Starter #9
So I was able to get down to the valves today after work and it looks like the valve seat on the intake is completely loose. So does this mean that the compression from the cylinder is blowing oil back through the valves and up through the breather hose?

Russ, please tell me this is good news! Best pics I could get. First one is the valve closed, second is opened and I pushed the seat up. So I am thinking that I still have good compression in the cylinder. I have zero experience with valve seats though.

Hoping for the best!
 

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Kish JD 318/420/430
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So I was able to get down to the valves today after work and it looks like the valve seat on the intake is completely loose. So does this mean that the compression from the cylinder is blowing oil back through the valves and up through the breather hose?

Russ, please tell me this is good news! Best pics I could get. First one is the valve closed, second is opened and I pushed the seat up. So I am thinking that I still have good compression in the cylinder. I have zero experience with valve seats though.

Hoping for the best!
Yes that will allow the gasses to blow back up in to crankcase/breather to air box.

That is a problem, it is one of the other issues small engines have, valves seats coming loose. If you know how and can do the work your self, however it involves removing the valve and old seat, going up in size for the replacement seat and boring, then freezing (liquid nitrogen) the replacement seat, apply a seat bond agent (a loctite product) to the fresh bore for the seat, setting the very cold seat back into the block, letting come up to temp for 24 hours then cutting the seat. A good engine shop has and does this type of work.
 

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Discussion Starter #11
Yes that will allow the gasses to blow back up in to crankcase/breather to air box.

That is a problem, it is one of the other issues small engines have, valves seats coming loose. If you know how and can do the work your self, however it involves removing the valve and old seat, going up in size for the replacement seat and boring, then freezing (liquid nitrogen) the replacement seat, apply a seat bond agent (a loctite product) to the fresh bore for the seat, setting the very cold seat back into the block, letting come up to temp for 24 hours then cutting the seat. A good engine shop has and does this type of work.
Thanks again Russ, this sounds like I am in a better place than I was, even though I still have a motor with unknown hours on it. Gives me something to work on and I will also search for a shop near by that might be able to do this. Thanks for your help.
 

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my 1986 316 w B43e onan had a similar valve seat pop loose. was able to get an over-sized valve seat put back in.

lasted for a little over 3 years before my onan grenaded after 32 years, see threads and pics below

https://www.mytractorforum.com/12-john-deere-forum/482977-just-got-some-bad-news-re-my-1986-316-b43e-engine-need-help-ideas.html

https://www.mytractorforum.com/12-john-deere-forum/1199809-snap-crackle-bang-32-years-rip-1986-jd.html

J

________________________________________

2017 John Deere X738 60" auto-connect deck, johnny bucket
1986 John Deere 316, 50" deck, purchased jan 1987, B43e onan died 2017, re-powered w P216
2010 Cyclone Rake Z10
 

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Premium Member
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Discussion Starter #13
my 1986 316 w B43e onan had a similar valve seat pop loose. was able to get an over-sized valve seat put back in.

lasted for a little over 3 years before my onan grenaded after 32 years, see threads and pics below

https://www.mytractorforum.com/12-john-deere-forum/482977-just-got-some-bad-news-re-my-1986-316-b43e-engine-need-help-ideas.html

https://www.mytractorforum.com/12-john-deere-forum/1199809-snap-crackle-bang-32-years-rip-1986-jd.html

J

________________________________________

2017 John Deere X738 60" auto-connect deck, johnny bucket
1986 John Deere 316, 50" deck, purchased jan 1987, B43e onan died 2017, re-powered w P216
2010 Cyclone Rake Z10
Thanks jimbo, some good info there.
 

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Discussion Starter #14
Some from what I can tell, it looks like the largest valve insert was already installed. Something like a 1 9/16 and it also looks like the other side was welded/repaired. I guessing it was probably done at the same time. But this means that this problem was supposed to be fixed. It’s a little disappointing but I’ll just stay patient and keep a lookout first for shop that can fix my problem. Second maybe a used onan on CL.
 

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