Onan P218G refresh

1764 Views 23 Replies 8 Participants Last post by artfull dodger, 7 mo ago

Kmart6

Discussion Starter · 7 mo ago

I inherited a JD318 with Onan p218g. The hour meter says 500 hours, but I know the engine is a replacement, so the hours are unknown. I pulled the engine to inspect, clean, and adjust the valves. I have been trying to decide if I should just tear it down, re-ring/refresh/hone while I have it out or if I should hold off until I have issues down the road. It ran great when I pulled it and smoked a tiny bit on startup. Take a look at the scoring on the cylinder walls and let me know what you think. Compression is unknown. I know I should have tested it before I tore everything off.

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jdalchemist

· #2 · 7 mo ago

With cross-hatching still visible, there are probably only a few hundred hours on on either the new or re-honed (or rebuilt) engine. Unfortunately, the carbon deposits have caused an undue amount of scoring. Visually it difficult to tell the depth of the groove wear. Can you catch a fingernail on the grooves? To really evaluate things, the cylinders should be measured to judge whether they have been re-bored, or if maybe out-of-round cylinders were just honed. If oversized pistons have been used, they will be marked on the top. Are there rust spots along the bottom of the cylinders (from water setting in the engine) or just specs of dirt?
Harold

artfull dodger

· #3 · 7 mo ago

Does any of the scorring in the bore catch your finger nail when you run it across the score marks? If not, don't worry about it, button it back up and keep an eye on it unless you really want to do a full rebuilt. Onans do NOT like a half assed(for lack of a better term) rebuild like you can get away with on a Kohler. Do it right and by the book with every i dotted and T crossed. Just how Onans are, picky. Some minor smoke on startup is considered normal on brand new Vtwins these days. Only once I got more consistant smoke or compression numbers were down around 100 or less, would I worry about a full rebuild. What were your compression numbers like? Cylinder head/piston head decarbon and valve adjustments every 200 hours of use, along with keeping the front side of the jugs clean is paramount to long life from an Onan in a JD. Along with keeping your belly screen clean, or replace it if your lacking it.

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Kmart6

Discussion Starter · #4 · 7 mo ago

jdalchemist said:
With cross-hatching still visible, there are probably only a few hundred hours on on either the new or re-honed (or rebuilt) engine. Unfortunately, the carbon deposits have caused an undue amount of scoring. Visually it difficult to tell the depth of the groove wear. Can you catch a fingernail on the grooves? To really evaluate things, the cylinders should be measured to judge whether they have been re-bored, or if maybe out-of-round cylinders were just honed. If oversized pistons have been used, they will be marked on the top. Are there rust spots along the bottom of the cylinders (from water setting in the engine) or just specs of dirt?
Harold

artfull dodger said:
Does any of the scorring in the bore catch your finger nail when you run it across the score marks? If not, don't worry about it, button it back up and keep an eye on it unless you really want to do a full rebuilt. Onans do NOT like a half assed(for lack of a better term) rebuild like you can get away with on a Kohler. Do it right and by the book with every i dotted and T crossed. Just how Onans are, picky. Some minor smoke on startup is considered normal on brand new Vtwins these days. Only once I got more consistant smoke or compression numbers were down around 100 or less, would I worry about a full rebuild. What were your compression numbers like? Cylinder head/piston head decarbon and valve adjustments every 200 hours of use, along with keeping the front side of the jugs clean is paramount to long life from an Onan in a JD. Along with keeping your belly screen clean, or replace it if your lacking it.

I will check back in this evening if I can catch a fingernail on them. I ran my finger over it and couldn’t feel it that way. Also, those particles are just dirt from after taking the head off. I cleaned it off after the picture. Definitely planning to decarbon and adjust the valves. I don’t have a bore gauge, but maybe I can find on cheap that could give me a ballpark measurement.

Oh another reason I pulled it is because one of the oil pan foot mounts were broke on the front.

artfull dodger

· #5 · 7 mo ago

You can check the bore to see if its oversize, but you need the pistons out to check for out of round condition as these is most evident at the bottom of the bore where the side loads on the piston head are the greatest. Whats your plan for the broken foot? JB weld or can you or a friend TIG weld?

chuckv

· #6 · 7 mo ago

You might be able to borrow a bore gauge from a local auto parts retailer...

Kmart6

Discussion Starter · #7 · 7 mo ago

artfull dodger said:
You can check the bore to see if its oversize, but you need the pistons out to check for out of round condition as these is most evident at the bottom of the bore where the side loads on the piston head are the greatest. Whats your plan for the broken foot? JB weld or can you or a friend TIG weld?

Ahhh okay. Hmmm. Decisions.

I don’t really have a plan yet. I don’t have any friends that weld and I’ve been looking at used oil pans, but they are pricier than I thought. I’m not really in any hurry to get this thing put back in. Just a side project

artfull dodger

· #8 · 7 mo ago

Any good welding shop, if you have one local to you, should be able to Tig weld the foot back on. Other option is to get it really clean and JB weld it back on, or a pricy good used oil pan. Have you put a wanted post in the classifieds here? Ebay prices can be silly money. Has to be a blown up engine out there with a good pan on it but the rest of the block is scrap.

dhager4692

· #9 · 7 mo ago

artfull dodger said:
Whats your plan for the broken foot? JB weld or can you or a friend TIG weld?

I agree with Artful Dodger. I went to a welding shop and for $20.00 he welded it in about 20 minutes.Still good.

artfull dodger

· #10 · 7 mo ago

Just fully degrease the pan first. No shop wants to take on a nasty, oily or dirty small job. If its nice and clean, ready for them to weld up, you will have better luck getting the shop to do the work.

Kmart6

Discussion Starter · #11 · 7 mo ago

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artfull dodger said:
Just fully degrease the pan first. No shop wants to take on a nasty, oily or dirty small job. If its nice and clean, ready for them to weld up, you will have better luck getting the shop to do the work.

Will do. Update, I checked both cylinders. No scoring catches a nail. There seems to be a little oil leaking into the cylinders after sitting. Is that a big issue?

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artfull dodger

· #12 · 7 mo ago

looks nice, still see cross hatch pattern in the cylinder walls. Oil getting past the rings when it sits for awhile is a sign the oil control ring(bottom most ring) is either a bit sticky from lack of use or worn. Guys like to try running Seafoam to free up the sticky rings, A good workout mowing at full power can help with sticky rings. But if in the past the engine was run hot by either being dirty or not being run at full throttle when under a load, the rings can loose their temper and will never seal up right again. Or, you might have a bore that is near or beyond the max allowable diameter and the block needs bored oversize and new pistons and rings fitted.

Kmart6

Discussion Starter · #13 · 7 mo ago

artfull dodger said:
looks nice, still see cross hatch pattern in the cylinder walls. Oil getting past the rings when it sits for awhile is a sign the oil control ring(bottom most ring) is either a bit sticky from lack of use or worn. Guys like to try running Seafoam to free up the sticky rings, A good workout mowing at full power can help with sticky rings. But if in the past the engine was run hot by either being dirty or not being run at full throttle when under a load, the rings can loose their temper and will never seal up right again. Or, you might have a bore that is near or beyond the max allowable diameter and the block needs bored oversize and new pistons and rings fitted.

so what would you do in my position. Read it apart and measure everything. Or clean it up/adjusts and slap her back into service

artfull dodger

· #14 · 7 mo ago

I would button her back up, and run the snot out of her. Do not idle the engine much, these engines like to run at full bore and be worked. Onans were designed for generator duty. So keep her clean, adjusted and work her hard. Some Seafoam in the oil might help if things a bit sticky with the oil control rings. Make sure you belly pan screen is clean, if its lacking one and you mow, get one or make one. Helps keep chaff and trash out of the engines cooling fins

vbosch

· #15 · 7 mo ago

You have it this far apart, a quick hone and a set of rings will keep it going for quite a few years.

artfull dodger

· #16 · 7 mo ago

But if he going to yank the pistons, then you need to be measuring the bore and checking for overall diameter and out of round. If that is out of spec, then your looking at a total tear down to bare block and machine work/expenses

Kmart6

Discussion Starter · #17 · 7 mo ago

One other question. Since I might be looking at buying a new oil pan, would I be better off sourcing a b43G oil pan just incase the starter mounts on my p218g break in the future (I hear that’s a common issue)? And can I use the p218g starter with b43g oil pan until that happens and I need to get a starter that mounts to the pan instead?

charms

· #18 · 7 mo ago

I wouldn't say the starter mounts breaking on a P218 is a common issue, but it does happen. Yes, you should be able to use the P218 starter with the B43 oil pan.
With the B43 oil pans, the oil fill/dipstick tube is tight in the pan, as opposed to the P218 pans where the dipstick tube has a rubber seal at the bottom. I have seen some B43 dipstick tubes that are around 1 1/2" shorter than others. These might have been the earlier ones. Later ones are longer, similar to the P218s. Either work, but the shorter ones are a little harder to check the oil with side panels on the tractor.

Kmart6

Discussion Starter · #19 · 7 mo ago

charms said:
I wouldn't say the starter mounts breaking on a P218 is a common issue, but it does happen. Yes, you should be able to use the P218 starter with the B43 oil pan.
With the B43 oil pans, the oil fill/dipstick tube is tight in the pan, as opposed to the P218 pans where the dipstick tube has a rubber seal at the bottom. I have seen some B43 dipstick tubes that are around 1 1/2" shorter than others. These might have been the earlier ones. Later ones are longer, similar to the P218s. Either work, but the shorter ones are a little harder to check the oil with side panels on the tractor.

gotchya. I just feel like if I’m going to by a new one, might as well just buy a b43g pan.

chuckv

· #20 · 7 mo ago

Be aware that there are two versions of the B43G oil pans, with the earlier one having only a bottom drain and no side drain. Your later 318 should have a hole in the frame matching the bottom drain, since the P218 pans have only the bottom drain. Each uses a slightly different dipstick a well.

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