| Author |
Message |
    
Nate Johnson
Member
Username: Wingrider
MN
Registered: 6-2007
Post Number: 397
| | Posted on Thursday, July 22, 2010 - 11:55 pm: | 
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Hey All,
As some may know, I bought an 87 318 with the P218 Onan in it. It had a knock, assumed it was a rod, but didn't have the loud knock usually associated with a bad one.
Today I tore the motor out of the tractor, got it up on a portable work bench, and after the darn thing fell to the floor due to the puppy, (carb took the hit) we started the tear down.
I popped the cover off that supports the crankshaft,(main bearing plate) and looking in, I could see bits of something in the oil pan. Looking in the cover, it looks like half the bearing is gone.
I took the rods off, and pushed the pistons out, and it appears that both rods are in good, healthy condition. I need to do some measurements to be certain the crank pto shaft is within spec, but I'm curious as to what to do about the rods.
This motor has an indicated 850 hours on it. Should I replace the rods while I've got it out, or simply leave them, and just re ring the pistons, and get a new main bearing?
I want to be smart about the rebuild on it, but don't want to be putting money into it that I really don't need to spend. When I bought the tractor I had figured if the motor was to rough and needed a major rebuild, I was going to swap some type of diesel into it, but if the motor only needed a little work, I'd fix it and either run it, or run it till I collected all the parts to do the diesel conversion and sell the motor.
If I didn't do rods, I'm looking at around $175. If I did rods, it would be around $350. I also have to figure in the price of a new fuel pump, and a carb, (or at least the top of the carb) so depending on new vs. used, it could make a fair difference.
So, what do you think I should do? Thanks for any help!  |
Kenny Andersen
Member
Username: Kennyrayandersen
TX
Registered: 7-2009
Post Number: 72
| | Posted on Friday, July 23, 2010 - 3:38 am: |
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Unless the bearing was gone so long that the rod got wore so bad that the new bearing won't work, I wouldn't worry about it. Check that the bore is round and if it is then you should be good to go (with new bearings of course). If they ain't round, then you probably need new ones. |
Bob Pataky
Member
Username: Bob421
CT
Registered: 6-2009
Post Number: 101
| | Posted on Friday, July 23, 2010 - 8:57 am: |
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Nate,
Being as the connecting rod is the bearing (no bearing insert used) have the connecting rod and crank rod journal measured. If the rod and crank are within spec you will be fine.
As far as the connecting rod is concerned the big end (crank end) very seldom is the problem area on theses engines unless destroyed by poor lubrication, the small end where the wrist pin attaches the piston to the rod is the end that needs to be inspected for wear and excess play.
Bob421 |
Nate Johnson
Member
Username: Wingrider
MN
Registered: 6-2007
Post Number: 398
| | Posted on Friday, July 23, 2010 - 9:17 am: |
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Thanks Bob and Kenny. Today I'm going to look over everything in the day light, and measure the crank, and take a closer look at the rods, including the top end. |
Nate Johnson
Member
Username: Wingrider
MN
Registered: 6-2007
Post Number: 399
| | Posted on Friday, July 23, 2010 - 8:12 pm: |
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Well, everything is within spec, so it got new rings installed, pan is back on, and I'm waiting for the local dealer to get the crank bearing in. Could have probably saved about $20 by going with the online Onan parts, but I got 7/8ths of the parts to put it back together today, and I work until it comes in anyway,so it all washes out. I'm guessing for under $200, I should have this motor back up and running right. |
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