Need some guidance. Setting valve lash on Onan P24

[Jeff]

Pretty sure thats my problem right now. Engine runs starts good until it warms up. then one cylinder start poofing and cutting out and spraying gas out the exaust. after the smoke, it smooths out and runs a little better for a minute then does it again. If you shut her down and let it cool a little, it runs good again.

Has someone set thier valve lash before on this model engine and if they have, can they give me a short tutorial on disassembly and settings and required gaskets?  I am guessing removal of intake and carb, and then it looks like there may be a valve cover to remove to set the lash.

[logwalker]

Jeff, Is that a T-260 model. If it is I have the service manual and can fax or email you the procedure. I would guess that it is the same for all the flat twins. Wouldn't you?  Joe

[Gary_C]

Chances are, the problem is not the valve lash, but you have carbon deposits on the valve stems that is causing one of the valves to stick open when it warms up. This unleaded gas has so little lubricating ability that too little clearance in your valve guides can cause the valves to stick. It can sometimes happen with a new engine.

Depending on the condition of the engine, it may not be economical to fix as many small engines do not rebuild very well. You could just try one of these new synthetic oils and even dump a little right in the cylinder. 

[woodmills1]

If it is carbon you can get a can of carbon remover from woodmizer, it works and will remove the carbon.  After that use mid grade gas to reduce carbon buid up.  However when my onan had a carbon problem it made a noise that sounded like a rod knock but higher up in the engine.

[twoodward15]

If it is carbon you could always use marvel mystery oil.  I don't know if it works but they claim it does.  My personal suggestion would be to pony up the $15 to $20 a can for "BG 44K"  this is a fuel additive product that works amazingly well.  I personally use it and can say it's the best cleaner around.  You might want to ask the people you buy it from if they still sell the spray that you can clean stuff with.  It's expensive but you wouldn't believe how well it cleans your engine.  Fill it up and let it run.  I'd also have to believe that it's not your valve lash.  Also, if you are getting gas coming out of your exhaust then it's gettting into the cylinder and not burning.  You could have a bad spark plug/coil/ plug wire. 

[scsmith42]

Jeff, I agree wit Twowood - it could be electrical, in addition to sticking valves.  I do not think that it's the valve adjustment.

If it were me, I'd put a spark tester inline to the plug (little piece of clear plastic with two electrodes in it that allow you to watch the spark.  Start the engine and let it run until it misfires, and watch to see if your spark disappears at the same time.  If it does, your problem is electrical.

Based on your other post, this engine has been sitting up for a while, right?  If so, your exhaust valves could be sticking a bit.  I would pull the exhaust manifold and spray some carbon cleaner up into the port to soften up the carbon, and then try to reach up in there with a stiff brush or something to work the carbon off of the bottom part of the valve stem.  You will want to rotate the engine over a bit (not start it - just rotate it) so you can be sure that you get all of the valve cleaned up.

Finally, I would pull the valve cover and spray some high quality penetrating oil on all of the valve stems, and keep rotating the engine over to help the oil get down into the valve guides.  Follow that with a high quality engine oil so that you have good valve to guide lubrication in place. 

Then put it back together and change the oil, using a high detergent oil.  Run it and enjoy.

[Kevin_H.]

Jeff,
when we adjusted the valves on the onan we called woodmizer and it seems they had the gasket kit for the valve job. I dont remember taking off the intake, but we did have to remove the muffler.

I dont remember what the clearance was  as I had the local small engine guy come out and do it after we got the gasket kit in.

[Fla._Deadheader]

Had a Onan on my first home splitter. EVERY time it sat for a while, one exhaust valve would stick. Had to pull the cover and "MARVEL" it. T'weren't no synthetic oils back in them days.

  I use Castrol Synthetic in both Honda mill engines. Change the filter every time and the oil every other time.

[highpockets]

About three months ago I went through this same type of problem with the 20 h.p. Honda on a sawmill.  There is a pretty extensive thread on this.  I finally installed some Champion 302 plugs and solved the problem.  I still think that there may have some valve sticking problem also.  My engine had been sitting for some three years. 

[cut2size]

Jeff, even if my answers are usually wrong, I have had a similar problem with an onan 24.  I removed the engine and took it to the local John Deere place.  The problem was one of the small bolts that are in the breather housing in a small tripod configuration had fallen out probably by vibration, and fell into the intake manifold through the carb.  It then lodged in the exhaust valve seat and my symptoms were the same as yours.  It was a quick and easy fix.
Hope that this helps
David

[Jeff]

Well, I think I am planning on pulling the exaust on the engine and see what I can see for a first step.

[twoodward15]

How are you making out Jeff?  Did you find anything yet?  Be carefull on the bolts.  I'm sure you're bound to break at least one.  I'll bet the Rust Reaper will really help loosen things up.

[Jeff]

I'm going to start with checking the compression. I dont have a tester so have to find one today.  I checked and saw my oil level doubled again. Full of fuel. I had that problem last year, I have a different carb now, a different fuel pump.  All I can figure is that I MUST disconnect the ful tank when I'm not running the mill. It has to be siphoning past the carb somehow and into the cyliders.  Probably because the tank gets pressurized when I close the vent and it sits in the sun is all I can think.

[Tom]

Don't close the vent and see what happens.

My problem was that the daytime made pressure and the night time made a vacuum.  The vacuum would suck the dew through the gaskets and contaminate the gasoline. That's why I put the glass bowl on the fuel line.  Then I found that the gasoline had a lot of trash in it too.  The sediment bowl made my filter last almost indefinitely.

[twoodward15]

I guess that'll do it.  That is also probably the cause of your bad running problem.  I guess you can't leave the vent open all the time?  Put a can over it or something to deflect rain and such?  Time to put a petcock on the tank or fuel line somewhere.  I'd fix that problem, change the oil, and run it again to see if you are still having misfires.  I'd be willing to bet that fuel in the oil is your entire problem.  

[isawlogs]

An outboard motor gas tank cap fits on there and it has an air realeese valve that you can open . Well it does on mine  ;)   Forgot to put the original back on once at the gas station  :-\

[Jeff]

Thats what my tank is, has the squeeze bulb and the quick connector and the whole spiel.

[jpgreen]

Every mill either gas or diesel should plumb in one of these...  8)

-Filter-

[GF]

JP, not sure if that 1" inlet and outlet is big enough for my small engine, do they make one larger?   :D ;)

[Jeff]

I was searching google for information on my onan, looking for tech sheets and such. Guess what I found when I thought I had found the answer?   The thread we started last year where I had this problem orignally. :D 

[scsmith42]

Jeff, after rereading the entire string, I'm wondering if your problem isn't a flooding carb?  If you're getting gas in the oil, then it's either leaking past the needle valve and flooding the cylinder, or coming through the fuel pump.

When the engine warms up if it's cutting out and spewing gas out the exhaust, then this too ties into a potential problem with the needle valve.

The common denominator between the two is the carb.

You might want to try putting in a good inline filter, and rebuilding the carb with a new needle valve and float, or at least pulling the old needle valve out and blowing out the line.

Scott 

[Jeff]

Different Carb. New Filter. New fuel Pump. I'm still leaning towards the valves. Just checking everything out.  Scott, this SEEMS to be a continuation of last years problems, discussed on this thread. https://forestryforum.com/board/index.php?topic=12878.0  Things got better last year but not right.

There is certainly no probleme with the guides as you can see in this photo. But I am wondering, (while I wait to get some feeler guages) exactly how the valve adjusts here? At first look, it seems that there are jam nuts that are loose, or are these likle bushings that thread into the lifters?  What locks them from turning?

[scsmith42]

From the pix I would guess that where the bolt screws into the follower ther eis some type of locking thread.

The inside of the engine sure looks clean.

If your valve clearances are way too tight, then you could be on the right track adjusting the exhaust valves, as the growth when hot could cause the valve to stick open.  BUT - thinking out loud here... the purpose of the carb is to mix gasoline and air to form a gaseous mixture.  That's what should be going into the cylinders.  If an exhaust valve is sticking open, although air fuel mixture could be leaking past it, theoretically it should not be spraying gasoline out the exhaust, becasue there shouldn't be any liquid in the cylinder to begin with...

How do the plugs look?  Are both the proper color or is one black and one gray?  If both are black, I would go back to the carb, fuel pressure, or electrical areas.  If one is black and one is gray, then I'd replace the plug and/or plug wire.

[twoodward15]

Just a guess Jeff, but I think the nut on the left closest to the valve) spins on a threaded shaft.  The shaft will move in and out and the nut is supposed to lock down on the seat at the right to lock the threaded rod in place so that it won't move.

[Jeff]

Both were similar in appearance but the misfiring cylinder plug was a little wet.  When I say gas is coming out, I mean you can see a an ever so slight spray, or maybe mist is better, when the engine coughs down. That lower exaust will smoke like heck, spray a little mist out, then catch and start running again.  Its like there is not full cumbustion in the cylinder and eventually the un burnt gasoline is getting spewed out. It only spews when it dogs and smokes.

[scsmith42]

Jeff, I just finished reading last years post.  There were a lot of good ideas presented on it.  The dirty carb pix were insightful too.

How many hours did you run the mill after cleaning the carb where it did not have a problem?  Also, did you ever replace your coil last year and also check out the grounding on it?  Any chance that more gook has gotten built up in the carb since it was last cleaned?

I think that you're on the right track to reset the valve clearance, if nothing else other than to eliminate this as a problem.  Running some Marvel oil down the carb after setting the valves won't hurt either, and you may want to try to dribble some onto the valve stems before you put the valve covers back on.  This could help free up any gum in the guides.

I can't help but come back to electrical or mixture based on the way that your plugs looked.  Wish that I was closer, as this is a real mind teaser!

[Fla._Deadheader]

The part on the right is the "tappet" or "lifter". It has 2 flat spots for a wrench. The bolt that screws in is a really tight fit. It will not move without wrenches. The guide is inside the spring in the photo. THAT is where the valve will stick, if that's yer dillemmer. My old Onan had the 2 wire coil. It ran terrible. I changed it to a one wire coil and fixed that problem.

[Jeff]

Just checked the lash. Dead on. Didnt have to do anything to it. .013 on the exaust valve, same as the specs in my owners manual.

[jpgreen]

JP, not sure if that 1" inlet and outlet is big enough for my small engine, do they make one larger?   :D ;)

Yes-

For when your mill gets all big and full grown up Gary...  :D

In the mean time, just use reducers and brass hose barbs to get you down to the 5/16 or 3/8" what ever your engine gas line is.  Your engines will be happy, happy, happy..  

[Tom]

Did taking the pressure off of the tank change anything?

[Jeff]

It may have.  I have to change the oil yet again. This will be about the 4th time I have done it since last summer.  I'm going out to do that right now. We have 60's forcast for the whole week, with lows in the 40's. Sounds like spring is here.

[Tom]

Spring my foot!!   What are you doing out of the house?  You're going to catch your death!   :D

[Jeff]

Started the saw to warm it up for the first time since bringing it home from norms so I could change the oil. It smoked and spit and carried on. I shut it down changed the oil, started it up and it was fine, however I didnt saw with it, just let it run.  It just takes about two quarts to change the oil, I drained over a gallon out of it.

I did a compression test. around 90 lbs dry, 105 with oil, both cylinders. All I can figure at this point is that when I dont unhook the gas tank, but close the vent for transport, the thing is building pressure and forcing gas through the carb into the engine and its draining down the cylinders and the high contaminated oil level is causing the engine to run bad.

PUNT!

[WH_Conley]

How about unplugging the fuel line and letting the engine run out of fuel? Carb on mine was leaking off and washing down the lower cylinder wall, (the way the engine sets at an angle when out of gear). That way when you closed the valve if it builds up pressure it shouldn't do anything except fill the bowl on the carb.

[Jeff]

THats my plan right now, when I shut it down after running, unplug the tank and let it run out like you would a outboard boat motor. I want to keep an eye on it and see if I get gas in the oil during operation. If I'm getting gas in the oil while its running, I am really missing something somewhere.

[wiam]

I have seen fuel pumps not work properly when oil level is too high.  I have had gas in the oil problems with my Briggs if i do not turn off the gas.  

Will

[isawlogs]

 Jeff ...  I just got a brain -----  lets just say its unfroze ..   I have the books here somewhere for the onan engin .. let me look for um . I bought them when I got the mill ...  : :P

[isawlogs]

 Jeff I got the Service manual here and the parts manual  in front of me .. anything you need to know ... 

 

[Jeff]

Whats wrong with my engine?  ;D

[Jeff]

Ia there anything in it about gas in the fuel?

[isawlogs]

Ya .. sticky float ...  :P  Still looking  ;D

[jpgreen]

-Isn't the FF cool.

Here's Marcel miles and miles away with the engine manual, and you guys can sit here and figure out what's wrong... then all of us can sit at home and watch..  8)

[isawlogs]

 Compression for the P224 .. as in the book ... 75 to 115 

[Jeff]

Sounds like I'm right in the ball bark there then.

[isawlogs]

 Would you like a copy of this book  ???    :P :P :P :P

[Jeff]

Yes, where would I find one?

[isawlogs]

 In the mail if you send me somewhere to send it to .  ;D

[Jeff]

Can't you ask da pig when he gets there? ;)

[isawlogs]

 I want to see if I can get this to you before he gets here from you .  ;D :D
I have to go to town tomorow and will get a copy done and have it off to you hopefully in the morning ...
It covers ...  P216 , P218 , P220  and P224  Performer series

   Ya want the Parts manual .. it only covers the P224G



      Count down is on ...   I have it in the mail , the copy is better looking then the original  ;D

                                     Hope you brushed up on your french  ;D :D :D :D
 

[Fla._Deadheader]

You're Baaaaaaddddd, Marcel.  8) :D :D :D :D :D

[isawlogs]

 ;D ;D ;D ;)
  Aint as bad as you might think ... the pics are bilingual  :D :D :D :D

[MULE_MAN]

isawlogs



Your what I call a Good Ole Boy !!!   And that's a Good thing !!!  8) 8) 8)

[Fla._Deadheader]

   :D :D :D :D :D :D :D :D

[jpgreen]

................... ;D

[sawguy21]

DanG you, Marcel, that is funny :D :D :D :D

[Jeff]

I'm going over this engine with a fine toothed comb and I have discoverd a couple things that may or may not have anything to do with the problem, but I plan on correcting them.  There is a jury rigged ground originating from the side of box that contains the key switch and the hour meter and connecting to one of the bolts that holds the, lacking a better description, the guide pads where the power head slides up and down. From there there is another braided ground cable that goes out and bolts to the engine base. Neither wires are original.

The other thing is the coil wire was routed so if the power head was ever taken clear to the top, it could pinch it. It looks like it could have been pinched at one time, so I am replacing and re-routing it. 

The spark plug wires look to be a bit corroded on the plug end and dont "snap" on the plug. I'm replacing those.

Marcel, I ordered a tach from wood-mizer Monday through Sparks, and low and behold it came today and there was a bonus in the envelope.  an Onan Service Manual in English with my name on it. :D  So, I can hardly wait for yours to get here so I can use it to translate yours so I can get working on things. (Chet joke) ;)

[scsmith42]

Those poor ground wires may be the culprit - good luck and please keep us informed!

[isawlogs]

 I never said anything about the manual beeing french ....  I only asked if you had brushed up on your french ....  ;D ;)    But I never said anything about maybe adding to the envelope  :D :D :D

   Have you the wiring diagram for that mill  ???

[Tom]

Does he need to brush up on  his French for the wiring diagrams too, Marcel?  :D

[isawlogs]

 Question is , would you like to brush up on yours  ;D ;D ;D ;D

[isawlogs]

 Jeff ;
   How you comming along with the engin , have you found anything to help solve the problems you are or where having  eh?

[Fla._Deadheader]

  Marcel is in rare form, lately, EH ???  :D :D :D :D

[Jeff]

Other then all the gas in the crankcase I find nothing wrong. I have to think it is from the tank building pressure and pushing gas into the engine when it isnt running. It seems to be running fine right now, although I really have not sawn with it to speak of.

I have good compression, the valve lash was perfect, I have replaced coil wire plug wires and grounding wires. Hopefully something I have done was right.

[isawlogs]

  Hook that mill to the red truck , and head on up this way , I'll cover the gas bill and will set you up with a wack or two of pine and we will find what the issue is .  ;D

   How is your french reading coming along .  ;D ;)

[Jeff]

Aint got nothing yet Marcel.  :-\

[Jeff]

Hey! I just found out I can read French!  Thanks Marcel!  I cant pronounce it, and I can't understand a blame thing, but I can read it! It has pretty much all the same letters in it that I know from English. Pretty clever those French eh?

Whew, I am sure glad the pictures were in english. ;D

[isawlogs]

 Hope you can get something out of it ,  ;D
  I have another copy here of the Onan books , if anybody else is in need of them .