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Martin

onan project

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Martin

first of all some history on this subject. when i picked up the cub 682 recently i did a labor deal instead of cash for it. the labor deal was a single kohler rebuild. well the single kohler didnt happen (yet) but my boss asked me if i would do a onan replacement on a miller 225 nt welder. it came with a performer 16 originally and something went south and eventually it ended up partially dismantled and out in the weather with all the other machinery. (this was at the place i talked about a few months ago, see holder ag3 thread if your interested.....).

well he dropped of the welder and two other non running onans at the same time and then the fun started.

not knowing anything about onans, but willing to get burned while learning, i did a whole bunch of dismantling and surfing the web for info, not always in that order though.

i had a few unknowns, was the welder generator any good? was either engine suitable for replacing the junked one? was any engine even capable of running without a lot of work?

 

heres what ive learned after 2 full days on it......

 

the welder is junk. too much outdoor weather and the generator armature and field coils are very corroded.

 

one replacement engine runs really nice, 125 on each cylinder, it was originally a rv generator, lp gas powered, and an 'nh' series engine. its 24 hp, and physically bigger than the smaller 16-20 hp onans that wh uses. and has a tapered pto end crank.

 

the other engine is a t260 oman, similarin many ways to the rv one above, size, hp, actually almost the same engine with 'normal' clothes and straight shaft instead of tapered..... engine was seized, but i tore into it and found a cam gear with 1/3 of the teeth in the oil pan, looks like the oil pump left the debris alone so not much other damage. bearing surfaces look good, bores are just ok, minor rebuild required, but nothing i havent dealt with before on the kohlers. valve seats look good too.

 

and then the engine i pulled from the welder. onan p 216, full of mud and generally a boat anchor. but it has some good parts, starter, the cam/crank gear-(same parts as the t260), governor parts, and with some work the heads could be cleaned up, maybe, and the oil pan as well......

 

as soon as i discovered the welder condition, i called my boss, and after some discussion, he suggested relieving my frustration with a big hammer to everything, needless to say he only wanted the welder back (for the trailer that it was mounted on) and suggested scrapping the rest. i reminded him of a good runner, but didnt seem too interested as without a lot of changing around, is only suitable for using as a generator. he may take this back with the trailer......

 

the t260 has my interest though. ive researched a little and these engines are about 3 inches longer than the 16-20hp engines, and the crank centerline sits about 3/4 inch higher. this engine is almost complete, missing coil, wires, condenser and grass screen/venturi that bolts to flywheel. i will 'donate' the cam and crank gear from the 16 (same part) and pull this one down for a rebuild, small hone, maybe rings and a full gasket set. valves look good, needs valve seals though. i was out with the tape measure today and it will just fit in a c1x5 series (black hood) and i think the c175 parts tractor (almost) could be a guinea pig......

i need to work on the height though, as im about 1 1/2 inches too high at 22 inches for this monster. the length comes out at 20 something inches, cant remember exactly, but i have about 3/4 clearance at both the hood and dash tower. held up the blower housing next to the c125 and sure looks like a lot of engine in there. thats still a ways off though, might just rebuild it and sit on it for a while too..... 

heres some pics of the onan destruction thats temporarily taken over my garage.....

 

the rv generator onan....

 

post-4321-0-09601900-1365911104_thumb.jp

 

onan performer 16 from the welder, not performing any more.....

 

post-4321-0-46205300-1365911123_thumb.jp

 

post-4321-0-80579600-1365911142_thumb.jp

 

onan t260 pulled down some to investigate...

 

post-4321-0-93047900-1365911157_thumb.jp

 

post-4321-0-24008900-1365911174_thumb.jp

 

t260 back together, i really need to get a shot of this next to the 16 to show the size difference....

 

post-4321-0-66651200-1365911191_thumb.jp

 

post-4321-0-62865200-1365911208_thumb.jp

 

rv generator onan all back together, really would like to use this in something as its a sweet runner. just a lot of extra parts to source to make it look like a normal engine again, and then theres that pesky tapered shaft....

 

post-4321-0-22569800-1365911229_thumb.jp

 

 

 

 

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Martin

well ive started a rebuild on the t260. just a quick rebuild, replace the timing gears and freshen it up. almost got it totally disassembled, and the main area where it needs attention is the gears and timing side cam bearing is totally shot. doesnt look like any broken teeth made it into the oil pump, so thats good. rod journals look good. not sure on crank bearings yet as the crank still needs to come out.

heres some pics of the tear down......

 

post-4321-0-29123800-1366710222_thumb.jp

 

post-4321-0-75666000-1366710242_thumb.jp

 

post-4321-0-60668700-1366710262_thumb.jp

 

post-4321-0-73528900-1366710276_thumb.jp

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WH854

This will be good reading and informative.

Chas

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Martin

some more pics......

 

t260 in front and onan performer 16 behind showing difference in size, ive started to get the majority of the scum, dirt, fur etc off the t260....

 

post-4321-0-35598500-1366757294_thumb.jp

 

and side, performer 16 has 9 bolts holding the head whereas the t260 uses 10 studs.

 

post-4321-0-50800700-1366757313_thumb.jp

 

differences in heads, 

 

post-4321-0-50551200-1366757334_thumb.jp

 

starter differences, performer 16 ( with the attached solenoid) has different mounting. performer mounts on the bottom of the cylinder and the t260 mounts on the oil pan/sump.

 

post-4321-0-97992200-1366757353_thumb.jp

 

post-4321-0-27634400-1366757372_thumb.jp

 

differences in intakes 

 

post-4321-0-93753200-1366757392_thumb.jp

 

looks like the timing case/side cover is the same though, all governor/timing gear parts same. minor difference in camshaft, but could still interchange, upper valve train is larger. looks like all the parts damaged on the t260 are obtainable from the junk engine though, so at the moment i think the dollar out lay will be a minimum, which is good because my aim is to do this one on the real cheap. i dont want to redo bores and replace pistons/rings etc which they probably should be looked at. bores dont look too bad, but the ring end gaps are on the large side of good, pistons have some scuffing on the top land as well. ive seen worse and put worse back together that i use on some of my own stuff and they run just fine, just not quite as 'crisp' as a nice engine.... :hide:  its amazing with just a little work that an out of spec engine can indeed run just fine without smoking like a train and banging itself to bits. im sure there are many out of spec engines out there that are still running just fine and until they get bad enough to justify rebuilding, they will keep getting used and used with the owners being none the wiser.......

 

after all, the main purpose of this exercise is to get the thing running half decent for not much outlay. so the engine police can reserve their judgement until this thing doesnt work out well and im eating crow.......

 

ive started cleaning up some of the bigger parts of the engine, as soon as my crank gear puller arrives, hopefully the crank gear will come off in one piece, crank can be removed and the block will be ready to go in the tank at work to clean up as well. then it will be time to get some of it back together. i wont be doing rings, everything will get cleaned up though, bores will get deglazed, replacement bearings for the cam and seeing how proud onan is of their gaskets, the majority of them will be made from gasket material. i will need to purchase head gaskets though, along with crank seals, valve stem seals and some other misc stuff.....

 

hopefully the rest will come out this clean...

 

post-4321-0-56865200-1366759919_thumb.jp

Edited by Martin
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MarkPalmer

If the bores aren't too badly out of round and you can get new ring end gaps .020 or under after deglaze, it should be OK as far as that goes.  Biggest concern will be crankpins, as if they are too much out of round (more than about .001 or so) putting it back together without machining them for undersize rods often ends up with an engine that fails quickly, making any work done not worth the effort.  Was it the bad bearing that made it shread all the cam teeth?  Looks like a fun project :)

 

-Mark-

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sorekiwi

Interesting thread Martin.  I was impressed with my 520's Onan when I pulled it apart, it is a nicely made engine with some good ideas.

 

If you get stuck for a crank gear puller, I can lend you mine (made for the P220).

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Martin

thanks mike. i ended up buying an onan puller, just waiting for it to arrive in the mail. 

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MarkPalmer

I would be curious to see what the main and rod bearing journals and crankpins mic out at.  Something along the line caused that cam bearing to run dry- REAL dry.  And the odds that other bearings weren't effected also.... you know where the engine cops are going :)

 

-Mark-

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Martin

got my crank gear puller in the mail today, so off came the gear and out came the crank. boy those gears really are on there tight. the puller is really the only way to get that thing off. everytime i put a bunch of tension on that gear, it just let out a loud crack as it moved off and relaxed tension.

onto the crank. well the journals and bearings look good, no evidence of anything like the cam bearing, i will let the pics show. there is a small amount of what looks like speckled metal in some areas, probably the result of the cam gear disintegrating......

 

mark, as far as that bearing starving for oil, I'm in no way an expert on bearings or engines for that matter, know just enough to get me in trouble, the bearing looks like the shell delaminated from the bearing surface..... the cam bearing journal i have pictured below and doesnt look out of the ordinary to me. its also only let go on the timing side of the engine, the pto side cam bearing is fine.....i remember reading somewhere recently that these engines were notorious for cam gear teeth removal for some reason, but maybe the two arent related. maybe the bearing was defective? like i said no expert, but ive seen bearing journals look a whole lot worse from oil starvation.

any one else have some interjection here on any of this?

 

bustin' off that darn gear.......

 

post-4321-0-18622100-1366941122_thumb.jp

 

crank as removed from engine, havent touched journals other than wiped off oil.......

 

post-4321-0-90114600-1366941144_thumb.jp

 

this is the cam from engine showing journal where bearing was shot......

i picked up most of those missing teeth from the oil pan.....

 

post-4321-0-58350000-1366941756_thumb.jp

 

both crank bearings......

 

post-4321-0-17786800-1366941178_thumb.jp

 

post-4321-0-72388500-1366941193_thumb.jp

 

typical of both rod journals.....

 

post-4321-0-60052000-1366941208_thumb.jp

 

post-4321-0-48008800-1366941224_thumb.jp

 

crank ends cleaned up to remove rust...

 

post-4321-0-38764600-1366941242_thumb.jp

 

block ready for a bath....

 

post-4321-0-09659500-1366941261_thumb.jp

 

 

also measured journals, i dont have what i consider a real accurate measuring tool, just my digital calipers, but i was consistently getting within a thou the same measurements at 90 deg to each other on all the crank journals. main journals were running 1.999 to 2.000 (spec min 1.9992 to 2.0000). connecting rod journals 1.625 to 1.626.... (spec 1.6252 to 1.6260). 

like i mentioned, not sure how accurate my calipers are though, theyve been consistent in the past on my kohlers. im no professional engine builder, just a tinkerer (as my wife calls me now) and i dont have all the measuring equipment that i really need, but ive managed to get by so far. all my rebuilds i couldnt be happier with and there all still going strong. i dont have a big investment in any of them with machine work, and if one of them ever lets go, well so be it. 

this engine is no different than the others, just trying to give a new lease of life on something that maybe would have otherwise ended up in the scrap pile.......

 

thats as far as ive got with this one for now.....

Edited by Martin

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MarkPalmer

The other sleeve bearings look pretty good visually.  I looked in my GE "Diesel Engine Bearings a Guide to Inspection and Analysis," book, (applies to all sleeve bearings) and the cam bearing that failed suffered thermal destruction- in other words it seized.  Why, we don't know.  An excellent investment, and also dirt cheap for working on small engines (or anything else) is the 3 micrometer set, and the telescoping gage set at Harbor Freight, less than $50 for both.  Their quailty is actually very good for Harbor Freight. 

 

-Mark-

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Martin

thanks for the tip on the measuring tools, mark. i have a digital harbor freight 6 inch caliper right now, but im suspect on its accuracy. i go back over measurements and double check and measurements change sometimes. i took your advise and went and got the telescoping set but they didnt have a 3 piece micrometer set, so i purchased another 6 inch caliper but dial this time. much more consistent.

friday was spent with the block in the strip tank at work. this does a good job of taking care of the messy stuff that otherwise i would have to do by hand. i found some time on my breaks to bead blast the somewhat rusty replacement timing gears from the performer 16 and the flywheel was masked off and blasted as well. yesterday i spent time pulling the 16 apart to salvage any usable parts as well as get the cam bearings out to replace the bad one on the t260. both cam bearings in the 16 were nice. 

i removed the bad cam gear from the cam and cleaned up all the governor parts ready to install. the t260 used a steel flyball spacer so i will be reusing that on the 16 gear instead of the plastic one that was on it originally. it will be loctited on to avoid the common spinning problem these governors have without the locator the plastic later year spacers have.

heres a thread on the fix over at weekend freedom machines forum.....

http://www.mytractorforum.com/showthread.php?t=260975

 

heres some more pics for those who dont like to read.......

 

block reasonably clean now, it will get a final clean after a light hone.

 

post-4321-0-18862400-1367159056_thumb.jp

 

flywheel with a light coat of black. was extremely rusty and looks much better now. had to mask off the magnets on the inside to protect them while blasting. ring gear only has overspray on it, inside the teeth is almost bear metal so i don't have problems with the starter gear.....

 

post-4321-0-05136500-1367159075_thumb.jp

 

governor parts to be reused....

 

post-4321-0-38554100-1367159100_thumb.jp

 

differences in cam gears from the cam gear that was on the t260 (one with broken teeth)  and replacement gear from the 16 with the flyball locator recess in the gear. this wont be needed as im using the older steel spacer from the 260 on the replacement gear. it will be loctited as in the wfm link above.....

 

post-4321-0-12717700-1367159119_thumb.jp

 

now its onto cleaning the rest of the internal pieces and tracking down some replacement parts.....

 

 

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Martin

update. got a new set of std rings for each cylinder, these were purchased from 'gary's place'.. they sell a lot of onan parts online, aftermarket, apparently as good quality as onan oem supplier, according to the owner, gary, who i talked with on the phone before purchasing just to see if i could find out a little more about these rings. they are made here in the us, he wasnt real sure of the exact supplier, seem to me to be hastings or similar.

honed the bore to a reasonable finish, came out looking ok, even 45 cross hatch from top to bottom, got rid of 99% of the ring marks and scoring in the bore, not perfect, but im ok with it. checked bore to piston clearance at 1.187 below top of piston and 90 degrees to the pin and we have......

 

cylinder 1..... piston 3.555   bore 3.563 (max honed std spec is 3.563)   clearance .008       (spec min .007  max .009)

cylinder 2..... piston 3.556   bore 3.563                                                    clearance .007

 

the ring clearance in groove averaged between .003 and .004 (min .002  max .008)

the only area of concern is the ring end gaps are still on the large side even with the new rings. the old rings gave me around .045- .048 on the top ring on both cylinders. right now im at .026  with the new rings. ( spec min .010 max .020)    ive been doing a little online reading about gaps with air cooled engines and I'm going to leave them as is. most opinions are that as long as the piston to wall clearances are within spec, then larger than spec ring gaps are of minor concern (within reason, of course). while being on the minimum side of spec is better for cylinder pressure and therefore power, the whole gap isnt allowing combustion gases through, only .003 to .004 that is exposed in the bore (half the piston to bore clearance), the rest is sealed on the lower land of the piston by pressure....

 

also plastigaged my big end clearances and ended up at .002 on both.. spec is .002 to .0033. ive been told on these big bore onans a tighter bearing clearance is better than being on the loose side of spec, so if thats the case, im good here.......

thats all for now. probably going to take the block in to work when i go back wednesday and soak it in the ultrasonic tank to clean and then will start on the assembly.....

Edited by Martin

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MarkPalmer

The Onan Performers I have worked on have had the Mahle (or Mahle style) piston that is similar to the "D" style Mahle forged piston used in the Kohler Magnums and can be used as a replacement on the K series.  As far as that goes, they work well on a used bore and I've never encountered any slapping or other issues with them.  The rings should have end gaps less than .020 if the bore is within spec, I usually come up with around .015-.018 on a used bore.  But if you are using "service" rings, it will probably be OK with the end gaps a little larger. It is important that the oil rings be the multi-piece style (usually included in a service set) with expander spring as these rings not only have no end gap when assembled but they flex well in used cylinders that are all slightly out of round.  If it's a single piece oil ring the odds of them working without the engine using a lot of oil are slim if the end gap is that large. 

 

-Mark-

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Martin

im not sure what type of pistons these are, other than they are the older style with the wider .078 rings. the oil ring in the set is the multipiece for better oil control. the pistons dont look like they have any wear at all on the skirt/area below the oil ring groove. i have some scoring above the top ring groove that i will tidy up a little but thats it. 

 

post-4321-0-91581600-1367845699_thumb.jp

 

post-4321-0-08578400-1367845730_thumb.jp

 

post-4321-0-80977900-1367845743_thumb.jp

 

post-4321-0-68092700-1367845760_thumb.jp

 

 

 

 

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MarkPalmer

Those are the older style pistons, but you have a service ring set so as long as the thrust face to cylinder wall clearance is in spec, which it looks to be, you'll be fine. (No sense in tossing out good pistons.)  I have found that three piece oil ring works wonders, no smoke right from the get go. 

 

These is some benefit to the newer style pistons.  Because the compression rings are thinner, they flex better and create less friction to the cylinder wall which equals less heat. 

 

-Mark-

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Martin

alright, lets get up to date on this thread. got all the parts i need to start putting this together, rings (above), gasket set, managed to get another complete free onan engine, an older NHE, (same size and generally the same engine as the one im rebuilding) for parts. engine was another to get operational but was rusty in the bore and therefore became a pile of parts. got good exhaust valves, all ignition parts, oil filter housing and all parts needed to convert this to a oil filter on engine rather than the current remote setup, which i dont have complete.

ive been really lax on taking pics, only just took some today and this thing is almost back together. still not certain this is going to be a good runner, but only time will tell. i really miss the simple kohler design and this things have just too many tight tolerances. most all of it is within spec, but ive cut a few corners and we will see if it bites me in the rear or not.........

 

heres a few of the progress......

 

engine almost back together, all bottom end done, ready for heads to go on...

 

post-4321-0-19187600-1374965041_thumb.jp

 

resurfaced heads, didnt need much work, two of the straightest heads ive come across..

 

post-4321-0-87862300-1374965057_thumb.jp

 

cleaned up valves, intake was ok, used exhausts from the other engine as they were in nicer condition.

 

post-4321-0-98480900-1374965091_thumb.jp

 

post-4321-0-88261800-1374965109_thumb.jp

 

heads on. these engines use a lot of washers, the top six studs use a thick washer and two cupped 'compression' washers, the lower four studs use just the thick washer. upper six torque values are different from the lower four as well.......

 

post-4321-0-82047700-1374965127_thumb.jp

 

 

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dennist

Nice post to read with good info on your rebuild.

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Martin

got a little more done, trying to get this thing buttoned up and see if it runs ok. still have to modify the sheet metal to fit around the oil filter as this engine originally came with a remote filter setup. i raided the parts onan nhe for the oil filter adapter and sheet metal drain. i probably will use the rusty nhe sheet metal for a pattern for the cutout. handy to have multiple engines of roughly the same type laying around.

since the last pics got the valves adjusted, valve covers on, resealed the intake manifold by using the same method as another member on here, basically drilling out the 'rivets' holding the halves together, cleaned up all the sealer, and resealed with ultra black rtv and re riveted with 1/8 aluminum pop rivets.

 

thread i used for reference here ( thanks wheeledhorseman)........

 

 

installed manifold, carb, starter and oil filter assembly and a few other brackets and linkages.......

its starting to show how tall this engine is, the aircleaner adds some more height as well. i thought about trying to remove the carb spacer, but i would need to modify the governor/carb linkage and maybe move the ignition coil. i will deal with that situation once i know i have a good runner and decide what tractor its going into....

 

post-4321-0-60766800-1375483184_thumb.jp

 

post-4321-0-42239000-1375483201_thumb.jp

 

post-4321-0-11485600-1375483217_thumb.jp

 

post-4321-0-10124100-1375483232_thumb.jp

Edited by Martin

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Martin

tins powdercoated and started to put them on. i painted up the exhaust with high temp powder as well. at least i will have some nice looking parts to sell if this thing runs like crap......

found a smaller oil filter that would fit behind the tins, i didnt want to cut them up just incase this all doesnt go as planned......

 

post-4321-0-86242700-1375923375_thumb.jp

 

post-4321-0-58982400-1375923592_thumb.jp

 

post-4321-0-14112100-1375923407_thumb.jp

 

post-4321-0-03297100-1375923425_thumb.jp

 

post-4321-0-63618200-1375923437_thumb.jp

 

 

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312Hydro

Sure is nice to look at. I'd say it will be running great with all the attention you've given it.  Can you post some video once you fire it up? Nice work as always.Martin. :handgestures-thumbupright: :handgestures-thumbupright:

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woodchuckfarmer

Very nice job looking good

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