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Need some guidance. Setting valve lash on Onan P24

Started by Jeff, April 08, 2006, 08:55:55 PM

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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.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

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. 
Never take life seriously. Nobody gets out alive anyway.

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.
James Mills,Lovely wife,collect old tools,vacuuming fool,36 bdft/hr,oak paper cutter,ebonic yooper rapper nauga seller, Blue Ox? its not fast, 2 cat family, LT70,edger, 375 bd ft/hr, we like Bob,free heat,no oil 12 years,big splitter, baked stuffed lobster, still cuttin the logs dere IAM

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. 
108 ARW   NKAWTG...N      Jersey Thunder

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.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

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.
Got my WM lt40g24, Setworks and debarker in oct. '97, been sawing part time ever since, Moving logs with a bobcat.

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.
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

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. 
Louisiana Country boy
homemade mill, 20 h.p. Honda & 4 h.p. for hydraulics.  8 hydraulic circuits, loads, clamps, rotates, etc.

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
cut2size

Jeff

Well, I think I am planning on pulling the exaust on the engine and see what I can see for a first step.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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.
108 ARW   NKAWTG...N      Jersey Thunder

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.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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.  
108 ARW   NKAWTG...N      Jersey Thunder

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  :-\
A man does not always grow wise as he grows old , but he always grows old as he grows wise .

   Marcel

Jeff

Thats what my tank is, has the squeeze bulb and the quick connector and the whole spiel.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

jpgreen

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

-Filter-
-95 Wood-Mizer LT40HD 27 Hp Kawasaki water cooled engine-

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 
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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 
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

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?


Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

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.
108 ARW   NKAWTG...N      Jersey Thunder

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.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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