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Went To Adjust The Valves On My Onan And?


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#1 dropped82 ONLINE  

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Posted August 20, 2013 - 09:39 PM

Well, my 446 has been running kinda funny. Puffing smoke and only running on one cylinder while cold at low idle. Once warmed up it runs on both just fine. I figure its due for some decarbonizing and valve adjustments. Got the gasket kit and started the tear down. Everything going good till I pulled the heads. I found what looked like oil seepage around the pistons on both sides. Being the configuration of the cylinders, is this normal? Definitely needs the carbon cleaned. Haven't checked the valves just yet. After seeing that oil, I wonder if I should get some rings? Any suggestions? Basically oil is around the rim of the piston when I spin it by hand.
uploadfromtaptalk1377052682113.jpg

You can see the oil in the bottom of the pic. Both sides are like this. The cylinders have a few scratches in them but nothing I can feel with my fingernail across them. The scratches could definitely be honed. Just wondering what you all think.

Eric

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#2 OkieGt OFFLINE  

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Posted August 20, 2013 - 09:53 PM

Well, my 446 has been running kinda funny. Puffing smoke and only running on one cylinder while cold at low idle. Once warmed up it runs on both just fine. I figure its due for some decarbonizing and valve adjustments. Got the gasket kit and started the tear down. Everything going good till I pulled the heads. I found what looked like oil seepage around the pistons on both sides. Being the configuration of the cylinders, is this normal? Definitely needs the carbon cleaned. Haven't checked the valves just yet. After seeing that oil, I wonder if I should get some rings? Any suggestions? Basically oil is around the rim of the piston when I spin it by hand.
attachicon.gifuploadfromtaptalk1377052682113.jpg

You can see the oil in the bottom of the pic. Both sides are like this. The cylinders have a few scratches in them but nothing I can feel with my fingernail across them. The scratches could definitely be honed. Just wondering what you all think.

Eric

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Better think about rods as well, as new rings with old rods spells trouble, Hope you dont have a seizure when you get a price on rings


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#3 dropped82 ONLINE  

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Posted August 20, 2013 - 10:05 PM

The rings are just under 50 shipped. Its not as bad as I thought. I was thinking rods too but I have seen early style rods go a long way with proper care. Only when the maintenance (cleaning carbon, adjusting valves, etc) is not done are there failures. This tractor is now at the proper maintenance mecca since its entered my herd. Hence the tear down. I did this now before it became a bad problem.

Eric

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#4 OkieGt OFFLINE  

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Posted August 20, 2013 - 10:28 PM

The rings are just under 50 shipped. Its not as bad as I thought. I was thinking rods too but I have seen early style rods go a long way with proper care. Only when the maintenance (cleaning carbon, adjusting valves, etc) is not done are there failures. This tractor is now at the proper maintenance mecca since its entered my herd. Hence the tear down. I did this now before it became a bad problem.

Eric

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Have you checked the tolerances on the rods or just eyeballed them? since you have it torn down might as well check to make sure, cause if a rod goes south, its a 3000.00 repair. Not sure how you scored a complete 2 sets of  rings for 50.00, hope your not intending to just replace one side, not sure if that would be a good move. Good Luck!


Edited by OkieGt, August 20, 2013 - 10:28 PM.

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#5 dropped82 ONLINE  

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Posted August 20, 2013 - 10:35 PM

Onanparts.com has them for around 22.00 per side. I haven't taken out the internals yet. Heck I still have to lift the engine out of the tractor. I will definitely be checking all the tolerances on everything when I pull the pistons and rods. Also I will definitely be doing both sides. An off balance Onan would definitely smoke some rods in no time.

Eric

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#6 OkieGt OFFLINE  

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Posted August 20, 2013 - 10:49 PM

Onanparts.com has them for around 22.00 per side. I haven't taken out the internals yet. Heck I still have to lift the engine out of the tractor. I will definitely be checking all the tolerances on everything when I pull the pistons and rods. Also I will definitely be doing both sides. An off balance Onan would definitely smoke some rods in no time.

Eric

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Glad to hear your doing it the right way, better safe than sorry, any shortcuts are expensive on a Onan, and any repair and parts are money well spent


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#7 546cowboy OFFLINE  

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Posted August 21, 2013 - 05:51 AM

Good luck and keep your fingers crossed. Last time I checked  a rod was about $90 and pistons with rings were @ $129, a gasket set was @ $140. It gets expensive fast with Onan. :reading_the_manual: :oh_shucks:


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#8 Mjoe7 OFFLINE  

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Posted September 01, 2013 - 02:51 PM

The following info is for those considering a Onan rebuild and what I learned from my experience.

Eric (dropped82) seems to have a good grasp of the following so it may not apply directly to him.

 

If your rebuilding an Onan a guy has to do some research and look other places for parts. If you go to a dealer be prepared to faint at the markup and cost of parts. Last I checked at my dealer a new DD carb for a B43M was $600.00!!! Pistons $300.00.

 

FYI If you have a shop rebuild it they add a markup to the parts they get as well. It's a good idea to have most all the big items before going this route.

 

My last Onan rebuild (B43M 16hp) I got new .020 over pistons .010 under rods on ebay for pretty cheap. I had a lot of machine work done to it and had the shop rebuild it. I had it align honed, decked, bored, crank turned, heads shaved, valves done, everything balanced rebuilt and assembled. Minus what I provided for parts the total was $1500.  but I have a better than new engine now with a little more power.

Good for 30 more years.

 

 

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#9 dropped82 ONLINE  

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Posted September 01, 2013 - 03:30 PM

That's a good info post there. I have done a ton of research and have sourced parts and talked to numerous people I know about the rebuild. Actually from talking to numerous people the oil I found is not necessarily too alarming. The cylinder walls are in good shape. I also have some symptoms that would point to a breather problem. My oil is as clean as can be with no signs of gas in it. Which would tell me I'm getting pressure in the crankcase. My plan is to pull the valve covers, check/fix the breather, and clean/hand lap/adjust the valves. Hopefully I will be good. After I hadn't run the tractor for a week I still had a slight pressure in the case. The oil being high on the dipstick after a week on not running was one indicator of that. At least I hope. Eric Sent from my SPH-D700 using Tapatalk 2

Edited by dropped82, September 01, 2013 - 03:34 PM.

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#10 Mjoe7 OFFLINE  

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Posted September 01, 2013 - 03:55 PM

Make sure the reed valve is functioning properly in the valve cover with the breather. 


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#11 John@Reliable OFFLINE  

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Posted September 01, 2013 - 04:38 PM

Make sure the reed valve is functioning properly in the valve cover with the breather. 

Any time I get a Onan they are on the list, I just figure might as well replace them when it's apart because I know they are going to fail sooner than later :smilewink:  



#12 Guest_gravely-power_*

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Posted September 01, 2013 - 05:08 PM

Onans are almost indestructable, if maintained. What I see from what you posted, If the cylinders mic out within tolerance,  hone it and install new rings. Don't listen to the naysayers as I have done this multiple times. Your Onan will last many more years!


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