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318 Onan P218 - Rebuild or Repower?


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109 replies to this topic

#1 Lawnguy OFFLINE  

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Posted September 13, 2011 - 04:00 PM

Hi everyone, Just wanted to say hey and introduce myself. I've spent a few hours searching the forums, so hope I'm not repeating something talked about already (know how that is!) I parked my 318 at the beginning of summer because I was smoking out the mosqueto's more then I was mowing. I thought at first I would just rebuild it until I found out how much the parts were going to cost at my local JD dealer! After tearing the motor down, it looks like I might be able to get by with just rings and intake seals, Cylinders looked okay, but the valves were all carboned up. I thought maybe it would easier to look for another motor or tractor and do a quick swap, but I'm finding that, that isn't easy to find either.

So my question is: Are there other makes of tractors that have the P218 engine I can look for? Are there other makes of engines that will fit with little or no rework? Or should I just try to rebuild what I have? Thanks, Dave

#2 olcowhand OFFLINE  

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Posted September 13, 2011 - 04:58 PM

Here's a place that specializes in such repowers with complete kits, en gine, pto clutch, and wiring adapters when needed.
John Deere 318 Outdoor Power Equipment Repower from Small Engine Warehouse

Not cheap kits, but easy to install. The Onan engines used on the 318 have large crank output shafts, which possibly no other Onan on other makes have, so with any Onan off another make is used, a new pto clutch would have to be used as yours would not fit. Only another P218 off a JD 318 would be a simple drop in.
If your bore mic's out good, and your pistons are still within spec, rebuilding your original engine would be the best route. I would replace all bearings, both crank & cam, replace the valve guides as well. Likely you're getting just as much oil consumption through your guides as past the piston rings. Take a good look at the valve faces & mic the stems too. Go through all measurement tolerances before making your decision which way to go. That's the only way to know the rebuild costs & get good results.

#3 Lawnguy OFFLINE  

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Posted September 14, 2011 - 08:51 AM

Thanks Cowhand for answering all of my questions. I've been putting this off all summer, and like my neigbor said the other night. Its hard to get motivated when you have your 400 sitting here in the garage...lol Anyhow, I think I will go ahead and just rebuild the motor. Make a winter project out of it. I've got it mostly tore down with exception of the crank, cam, bearings, and valves. So my question of the day is: Is there a special tool required in order to compress the springs of the valves in order to get them out? and if so, where can I buy one? thanks!

#4 olcowhand OFFLINE  

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Posted September 14, 2011 - 10:44 AM

This one would work well with most small L-head engines.
Lisle 23300 Valve Tool - Cylinder Head Tools
Sears carries the same tool for $20.89, so if shipping on the one above is high, you might just pick one up at Sears.

valve tool.jpg

#5 Lawnguy OFFLINE  

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Posted September 16, 2011 - 08:42 AM

Thanks, I'll head upto Sears this weekend and look for one. I want to look for some calipers as well so I can do the other checks you mentioned. Attaching a few pic's just so you can see what I'm working with. I've been taking pictures of every step of the tear down so I can remember how to put things back togeather. Not sure why, but I numbered the rods and pistons (something my dad told me when I was a kid).

IMG_43421.jpg

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#6 olcowhand OFFLINE  

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Posted September 16, 2011 - 08:45 AM

Not sure why, but I numbered the rods and pistons (something my dad told me when I was a kid).


I always do that myself!

#7 dsdillner OFFLINE  

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Posted September 17, 2011 - 07:10 AM

Hi I'm new to this forum but not new to the topic. I've done a few repowers of the 318 & 420 not using a kit as mentioned above. I have used both Honda and Briggs recently. I have found I can replace the engine and spend about the same as a rebuild. Now the big question we all debate is; which is better, a rebuild Onan or a new engine? From a fuel economy point of view the new engine wins. I also think from a longevity new engine also but lots of disagreement here but to make the Onan run as long as it did originally you will need to replace or verify that it all is as good as new. If you were to choose the new engine there are sleeves available to manage the shaft size difference so you can use your existing PTO clutch. My 2 cents

#8 Lawnguy OFFLINE  

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Posted September 19, 2011 - 08:10 AM

Thanks for the advise dsdillner. Can you give me direction on where I might look for the sleeves to adapt my clutch to various engines?

#9 dsdillner OFFLINE  

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Posted September 20, 2011 - 05:23 PM

Call T.H.E. company. They will sell you a sleeve that takes a 1" shaft to 1-7/16" shaft. They also do a very nice job on Honda kits and have great customer service. Ask for Paul or Jess. (I am not affiliated with this company nor do I get any bennifit)

Dan

#10 aprophet2 OFFLINE  

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Posted September 21, 2011 - 09:35 AM

What do you think an average "fair" price would be if I were to send my Onan P218 out to be rebuilt? Thanks!

#11 Lawnguy OFFLINE  

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Posted September 22, 2011 - 07:53 AM

Call T.H.E. company. They will sell you a sleeve that takes a 1" shaft to 1-7/16" shaft. They also do a very nice job on Honda kits and have great customer service. Ask for Paul or Jess. (I am not affiliated with this company nor do I get any bennifit)

Dan


Dan, I did a google search for T.H.E. company. Just wanted to confirm that your talking about the folks out in Mount Pleasant, Iowa?? thanks

#12 olcowhand OFFLINE  

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Posted September 22, 2011 - 08:59 AM

What do you think an average "fair" price would be if I were to send my Onan P218 out to be rebuilt? Thanks!


I would have no idea, as I do ALL my own rebuilds. Price for machine shops vary also, but member TD&H just had two crankshafts ground, rods & mains for $45 each crank. Last bore job I had done was $40. Last re-sleeve job I had done was $110. I can rebuild for WAY less $'s than hiring it, or buying a new engine.

#13 Jehtro OFFLINE  

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Posted September 22, 2011 - 09:33 AM

How many hours are on your 318?
  • truckintyler said thank you

#14 Lawnguy OFFLINE  

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Posted September 22, 2011 - 01:54 PM

How many hours are on your 318?


1230 hrs regeistered on the hour meter. I haven't checked everything out yet, but just my initial view once I tore down, was that one cylinder showed alot of carbon buildup on the intake valve enough for me tell that, that was the cylinder burning the oil.

#15 mikebramel OFFLINE  

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Posted September 22, 2011 - 02:54 PM

Well, with a flat cylinder it will inherintly burn oil. The oil doesnt have gravity draining it back like on a Vtwin or straight vertical cylinder




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