Onans - to rebuild or not

[Harry]

Hi gang, I have a bit of a dilemma. Let me explain. The tractors and engines I have at the moment are these:

Main tractor: 644. It came with a Kohler 14HP that seems to have been a John Deere edition. This engine doesn't smoke, feels strong and runs without a problem. Lacks the clutch but I had no thoughts of putting a mower deck on this one.

Previous main tractor: 446. This one has an Onan BF-MS which feels really strong, a beast with around 110 psi compression on both cylinders. Currently this is on snowcaster duty. However, I don't like this tractor because my clothes smell like exhaust after I use it. I've complained about it on the other site, and someone sent me a private message telling me that Onan engines are like that. Hard to believe right? But how can the very strong exhaust smell on me be explained, with strong compression and strong engine?

B38BECF1-BD5B-417E-B5F9-C5C1E353E955.jpeg




Tractor #3 is 224. This one has the K321 that I rebuild and runs awesome. This will be my mowing tractor I think.

Tractor #4 is a 444. My latest acquisition. All wheels need to be replaced, the TCV is stuck and probably needs to be replaced. Needs new seat, and painting. To my surprise the Kohler K321 on this machine is running like new. I'll probably make this the snowcaster tractor and sell the 446.

But!!! I have an Onan B43 engine that came with a parts tractor. The guy told me that it smoked badly when it was removed. Given that I've been so far happy with the Kohler 14HP, that I have plenty of, why would I want to rebuild the Onan 16HP? Is the large difference in price really worth it? Plus, will it still make my clothes stink even on a fresh rebuild?

What are your thoughts guys?

I've been waiting to read some of the reply's before posting my own. I get gas smell on me from any gas operated machine I use. My wife is always saying you smell like gas when I come in the house. I think it is because I mostly have older machines, but the direction of the exhaust has a lot to do with it. My Kohler engines direct the exhaust in the front and I do smell after using them. My 446 that I use for winter has the stock exhaust and is usually used out in the wind. Since I have a cab on it I don't get the gas smell on me and have never found to have any fumes inside the cab. If I did, I would direct the exhaust up a stack higher than the cab. My 646 has a CCKA Onan engine, which I rebuilt last winter. It has the exhaust in the front but it is directed to the side. No problem smelling any gas smell from that machine either. My two cycle gas machines like my leaf blower-vac, string trimmer and chain saw are another story. Oil mixed in the gas, smelly!

As an afterthought do any of you guys have OHV engines like the Briggs or Hondas? What are the results with gas smell from them?

Keep the Peace
Harry

[Eugen]

@Harry I do get a little smell on me from the Kohlers. But the Onan in my 446 is a different story, strong smell on clothes, unexposed skin, hair. As I said, sometimes, after doing work in the garden with the 446 I had to take a shower. A little smell like the K321 I have is not something I would complain about, even though I would prefer no stink at all.

[Gordy]

@Gordy you're not going to like this discussion

https://www.mytractorforum.com/threads/ ... od.236554/

I'll have to look farther, that Richard seems to have a large thorny stick up his butt I just looked up how to decode the serial #, the first 3#'s of the 8 digit code are 150 so that makes it a early 1985 model year. 85's are 150-159. So pretty darned good (fantastic) according to what Richard was saying

https://www.wheelhorseforum.com/files/f ... 5-2011pdf/


Gordy

[Eugen]

@Gordy yeah those guys were pretty pessimistic. By what I see parts aren't too bad to find, like this piston kit $49

https://isavetractors.com/piston-kit-fo ... i-engines/

and connecting rod also $49

https://isavetractors.com/kohler-kt19-m ... cting-rod/

another set of gaskets and rings (only std though) $150

https://www.ebay.com/itm/140975328541?h ... XQq8BQ7w74

The fact that it'll last another 20 years make prices not so bad. You might find even better prices if you shop around. If you go for it please open a thread on it, it'll be nice for us to see how that's done!

[DavidBarkey]

@ssmewing and @Timj sorry guys, I don't understand this. If both B43 and P218 are dirty engines, they both put out smell in the exhaust. My 446 has the tip of the muffler at the front of the tractor in that slot in the hood, on the left hand side. The 4 digit tractors have the exhaust coming out also at the front of the hood, but on the right hand side. Why would that make a difference? The air cooling the fins goes front to back in both tractors. Unless there are exhaust leaks at joints before the muffler exit, there should be no difference. Just trying to understand what you guys are saying.


The fact that at least two of you guys like the Onans so much makes me think I may want to give my 446 another try. Maybe a really good carb tune up, making sure there are no air leaks in the intake and exhaust joints would improve the stink.

The 3 digit tractors have the engine oriented flywheel forward, so the cooling air is directed back at you. With that air flow the exhaust gets sucked in with the cooling air, so the exhaust comes at you too. The 4 digit tractors have the engine turned around, flywheel to the rear. So the cooling air is blown forward and would push the exhaust away from you.


Gordy

What Gordy saying here is bang on .
Dave

[MattA]

As an afterthought do any of you guys have OHV engines like the Briggs or Hondas? What are the results with gas smell from them?

Keep the Peace
Harry

My 16HP Vanguard of 2001 vintage doesn't smell too bad. Certainly smells a lot less than the old 5hp tecumseh on my dads snowblower.

[Gordy]

@Gordy yeah those guys were pretty pessimistic. By what I see parts aren't too bad to find, like this piston kit $49

https://isavetractors.com/piston-kit-fo ... i-engines/

and connecting rod also $49

https://isavetractors.com/kohler-kt19-m ... cting-rod/

another set of gaskets and rings (only std though) $150

https://www.ebay.com/itm/140975328541?h ... XQq8BQ7w74

The fact that it'll last another 20 years make prices not so bad. You might find even better prices if you shop around. If you go for it please open a thread on it, it'll be nice for us to see how that's done!

Thanks for the links I did some snooping on "Isavetractors" and found the complete gasket set. $59.99

https://isavetractors.com/complete-gask ... kt17-kt19/

So in round #'s $260 not bad. It's been 6 or 8 years since I checked the local machine shop for prices to do a single cylinder engine, he quoted $75 to bore the cylinder, $45 for the crank and $75 for a valve job if the old valves can be reused. I forget what he wanted to clean up the heads if warped. So figure double that for the twin @ $200 + $260 = $460 and some busted knuckles for a good running engine. OH and those prices are me stripping the engine down to the bare block.


Gordy

[Eugen]

@Gordy consider yourself lucky to get your crankshaft journal done for $45!!! I paid 170 Canadian pesos for only one journal! but I have no regrets

[ssmewing]

@ssmewing and @Timj sorry guys, I don't understand this. If both B43 and P218 are dirty engines, they both put out smell in the exhaust. My 446 has the tip of the muffler at the front of the tractor in that slot in the hood, on the left hand side. The 4 digit tractors have the exhaust coming out also at the front of the hood, but on the right hand side. Why would that make a difference? The air cooling the fins goes front to back in both tractors. Unless there are exhaust leaks at joints before the muffler exit, there should be no difference. Just trying to understand what you guys are saying.


The fact that at least two of you guys like the Onans so much makes me think I may want to give my 446 another try. Maybe a really good carb tune up, making sure there are no air leaks in the intake and exhaust joints would improve the stink.

The 3 digit tractors have the engine oriented flywheel forward, so the cooling air is directed back at you. With that air flow the exhaust gets sucked in with the cooling air, so the exhaust comes at you too. The 4 digit tractors have the engine turned around, flywheel to the rear. So the cooling air is blown forward and would push the exhaust away from you



Gordy

What Gordy saying here is bang on .
Dave

If you kneel in front of a 4 digit tractor and compare that to a 3 digit tractor will see a major difference in exhaust plus cooling air. The 3 digit tractor even has a heat deflector shield that the 4 digit tractors do not have.

[ssmewing]

@Gordy yeah those guys were pretty pessimistic. By what I see parts aren't too bad to find, like this piston kit $49

https://isavetractors.com/piston-kit-fo ... i-engines/

and connecting rod also $49

https://isavetractors.com/kohler-kt19-m ... cting-rod/

another set of gaskets and rings (only std though) $150

https://www.ebay.com/itm/140975328541?h ... XQq8BQ7w74

The fact that it'll last another 20 years make prices not so bad. You might find even better prices if you shop around. If you go for it please open a thread on it, it'll be nice for us to see how that's done!

You will be going backward if you start replacing Onan parts with China parts. Onan is not a normal engine. Most of the time the piston and the rod are just fine. If you broke a rod you must fix what caused that to happen and get a matching used and plentiful rod as a replacement. Hastings makes better than original rings for the standard pistons. If the bore can be machine shop honed and not be over 0.005 from original specs a standard piston and rings will work just fine. If you go over 0.005 and need an oversized piston the first thing you would do is to try to find a better block. Most blocks will hone to less than the 0.005 spec. Good blocks can often be found for around $100 US. If the engine is very important to you and your best option then the only choice is to use the oversized Onan piston and rings.

Hastings rings are only sold through retailers. The hastings rings use a superior oil control ring system over the original Onan ring. Used matching parts are by far the best. The main guy for all things Onan is Boomer. http://boomersonanparts.com/

I re-ring and go through all my Onan engines. I do not add oil to any of them during use. If the oil gets to the add it means I need to change the oil. I even redo the valves to where they are watertight on the compression stroke when you fill the back cavity.

Lastly, some people have their carb screws way past where the service manual says they should be. The Onan will deal with this but burn dirty. The reason the screws are way past the service manual is a dirty carb and 99% of the time a leaking intake manifold. You have to split the manifold and reseal that. I cover most of this on either Facebook or Youtube under Hemlock Case Guy.

For Onan engines to stay as strong as Onan engines they must remain truly Onan engines and repair parts. Right down to points and the condenser, it matters.

Static timing or with a timing light helps with the heat as well. Feeler gapping is to just get it close. Out of time engines, all engines can cause them to run hot.