Just offered a 416H with a smoking habit...

[Theroundhousernr 589]

   I was just offered a 416H with around 370 hours on the meter. I believe that to be a little low but I don't think its much over 500, 600 hours. It smokes pretty good at all rpms but runs well with what seems to be good power. I was wondering what you guys think the problem could be?

 

  I am hoping for a clogged up breather or improperly assembled breather.

 

  Next thing coming to mind is bad valve seals.

 

  Or worst case scenario is rings shot or stuck,

 

   or all of the above. I am hoping for the first two.......

 

 

  Any thoughts guys? Would a compression test narrow down my check list??

 

  Want to have a game plan before I jump in on this one.

 

 

  Kyle

 

 

[KATO 115]

Compression test wont tell you for sure if its rings or valves.

You need to do a leak down test and listen to where it is leaking

....crankcase or exhaust or intake

[wrmhaste 235]

I just had an issue on my 520h last weekend. And I've heard a lot of issues with these onan motors. I would definitely do a compression test first. It's very simple and fast. It sounds like the exhaust isn't closing all the way. I would guess it's probably the rear cylinder giving you problems. These motors are suppose to be adjusted at 600 hours. Mine had plenty of power running on one cylinder unless got into real high grass. My intake wasn't closing. Hope this helps.

[WH nut 553]

You can do a wet and dry compression test. if you get a big increase with a squirt of oil it indicated bad rings. if its low with no increase you have worn valves.

[wrmhaste 235]

Very good idea whnut. I had completely forgot about that test.

[Theroundhousernr 589]

Wh nut, explain that test a little better for me. I think I understand,but need a better explanation on performing the test. Thanks Kyle

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At wide open throttle the smoke goes away but the second you idle down it comes back

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[wrmhaste 235]

Pull the plug on a cylinder,do a regular compression test,then put a squirt of oil in. I recommend marvel mystery oil. And do the test again. If the compression goes up you have a ring issue. If not it's a valve issue. Repeat on other cylinder. Hope this helps

[Theroundhousernr 589]

Duh now I get it

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[Theroundhousernr 589]

OK small update. Can not find the right adapter for the compression test. The breather was a little dirty but now clean. When started and left full throttle , it stops smoking after a minute or so. The moment you let the throttle down it starts smoking instantly. The smoke is not real blue... its more grey. Could this be a carb issue maybe???? I know wishful thinking. It seems like when its under vaccum , it starts smoking at lower throttle?

 

      Thanks Kyle

[Martin 2,130]

when you looked at the breather, did you see if the check valve or reed valve (depending on what setup you have-some are one style, some are the other) is working properly? also was there any evidence of oil in the air cleaner? or at least damp in there?

if the check or reed valve isn't doing its job it will allow oil to be sucked in and consumed through the induction system. I'm not sure if the oil consumption would be the same high vacuum and low vacuum though. if it only happens under vacuum it would be more chance that oil is getting to the combustion chamber from anywhere below the throttle plate and not above it. valve seals would be an area to look at.......

 

 

just re read your post above, maybe look at carb tune as well. richen or lean the carb a little and see what happens. hard to pinpoint issues sometimes without seeing and hearing the engine run.....

 

fuel pump internal leakage could be allowing oil to be consumed as well....

Edited June 8, 2014 by Martin

[Theroundhousernr 589]

  OK well. I just brought the 416H home today. Once hot, the engine only smokes when you throttle down. For instance, when you go from full throttle to 3/4 throttle. it puffs a big cloud then It clears up instantly. It will even idle without smoking.  But when you first start it , it smokes no matter what , then after a 30 seconds or so. It clears up....?

 

  The breather is clear and working. I did notice it was about 3/8 of an inch overfull on oil. Could that cause these issues? Runs great with no knocks or tapping. I did also take note that the smoke seems to be a grey color. Not very blue at all.

 

  Upon startup, it takes a lot of choke to get it running, but once hot. It seems ok. It does stumble pretty bad when you try to rev the engine, but once it reaches the target RPM. Its fine.

 

 Does anyone think this is carb problems and not problems with rings or valves. Also , there is no oil buildup in the air cleaner or inside that area for that matter. It has me stumped. Once I start thinking one area is the issue, something throws that theory off.....

 

   Thanks Kyle

 

  Also , I have had engines that smoke upon startup but they where overhead valve motors with bad head gaskets. When they would sit, oil would leak into the cylinders but after startup it was fine. Could it be valve guides or the seal on the intake valve? but again , its not blue smoke. Also, both spark plugs are completely black.

Edited July 17, 2014 by Theroundhousernr

[varosd 1,185]

  

[Theroundhousernr 589]

I can take some for you.... Now the ignition module just crapped the bag on me.   I guess I will focus my time on rebuilding my p218. It always something.....

[Theroundhousernr 589]

Ok here is some pictures. I just replaced my ignition module and got her going again. It was here for all but 20 minutes before the module went out on me. So back to the testing. Once again, smokes at startup but clears once warm. Once motor is warm it will only smoke when throttling down. It puffs a big cloud until target RPM is reached. If you throttle down slowly. No smoke. No smoke under load either. Clear as could be coming out the exhaust.

I did a compression test on the motor and both cylinders read 110 psi or so. Next step will be a leak down test as suggested. Once I get some answers from the leak down test. I will post them up.

Here is some photos.

Edited September 6, 2014 by Theroundhousernr

[Theroundhousernr 589]

Video.....

 

http://youtu.be/vFzBNd5DxLc

Edited September 6, 2014 by Theroundhousernr

[Molon_Labe 731]

Well, the engine sounds good. Smoking like it does when closing the throttle is commonly caused by higher vacuum pulling oil into the combustion chamber, usually pointing to valve guide/valve stem wear.

[pacer 3,160]

Yep what Bailey said on it being vacuum related - if you have ever had a vehicle with a vacuum gauge on it youll probably remember how when you let off the gas at speed how the needle would peg out, it throws a hack of a load on the combustion chamber and smoke like that usually points to stem/guides worn.

[Theroundhousernr 589]

UPDATE! UPDATE!

 

   After shooting the video for you guys. I was backing up the tractor to the garage to put it away for the night and it shut off and would not restart. I thought to myself, dont tell me that used ignition module I put in today crapped out to!. So I checked the gas because been there done that , if you know what I mean. Sure enough , It was out of gas! So I put some good ole ethanol free gas in. When I started it back up , immediatly the smoke had gotten better to almost gone. I ran it for a few seconds and the smoke cleared all together!!!! It now revs right up with no hickup. Does not bog down at all. Idles perfect.

 

            

 

  Must have been something in the fuel. The guy I bought it from purchased it from a man off craigslist. The man told him it just starting smoking out of no where. Did not know why, just wanted it gone. So he checked the breather, cleaned the air filter, changed the oil/filter and ran it around a little but it never cleared up. So he offered it to me. He didnt have time to rebuild it.  Fast forward and hear we are today with a 400 hour 416h   running beautiful. Thanks for all your suggestion. Maybe this will help someone one day to.

 

 

  Now the big question. What in the world would be in the fuel to cause this? Oil, water, kerosene, Diesel?  I could not be happier right now if you couldnt tell! lol

Here is a video for the proof!

http://youtu.be/gCQcVwkZS00
 

[Theroundhousernr 589]

I agree about the valves but onan motors are not none to wear out valve guides. Thats what had me stumped. Then again anything is possible. The guy I bought it from thought cracked piston.

[pacer 3,160]

Probably as simple as someone grabbing the wrong fuel can and got the mix one intended for the weed eater & chain saw, etc - that will sure cause some smoke tho usually will smoke constantly (dont ask how I know!)

[Theroundhousernr 589]

That's what is so weird. When it was hot enough it would burn clean. But then what would explain when I would throttle down?

[Theroundhousernr 589]

Well I fired it up this morning after it sat all night because I am still in denial that it was just bad gas. It fired right up and idled perfect. No smoke and sounds really strong. Never had such an easy fix for what I thought was a major problem. I am going to through a deck on it tonight and work it good. Then give it a good power wash and cleaning.

 

         I bet the guy I bought it from would never believe me. Maybe I shouldnt tell him.......  

Edited September 7, 2014 by Theroundhousernr

[oldredrider 2,547]

Just goes to show you can never assume anything! Bad gas is something you wouldn't have guessed to be the problem. Chalk another one up to experience.

[Theroundhousernr 589]

Put a little shine on it tonight. I guess this one is going to be hanging around now.

[Geno 1,928]

Glad you got it worked out and it was a simple fix!