YM240 smokes heavily, lacks power

   / YM240 smokes heavily, lacks power #31  
Usually the only way a push rod will bend is from something in the combustion chamber (chunk of carbon or something ingested past the filter etc) stopping the valve from moving or a stuck valve guide like from rust on an engine that has sat a long time and improperly vented.

I would say a sticky lifter could cause it also but unlikely since they sit in oil. Also I would doubt the valve in question is bent since the valves go straight down and the pistons are flat on top it would have just pushed the valve up out of the way w/o damage imho.

The worst thing a person can do on long storage of an engine is close it up tight IE stuff cap plugs in exhaust or intake or a tight fitting can on the exhaust pipe that causes lots of condensation inside.
 
   / YM240 smokes heavily, lacks power #32  
...drop it off for them to use while working on getting their home clear of muck. ...

I'm worried about the turf tires complete lack of traction in mud
I wonder if wrapping a coupe of tow chains around each tire would improve traction enough for that emergency project.

Has anyone tried this?

Also - if there is a loader and no rear ballast on this 2wd, hanging any sort of implement on the back will make a huge improvement in traction.
 
   / YM240 smokes heavily, lacks power
  • Thread Starter
#33  
Carey, I though about doing a compression check, but I don't have any of the equipment to carry out that procedure. It seems to run fine now, and fires up fairly quickly, so I think the compression is at least acceptable. I'll look into finding the apparatus to do a compression test though.

When I started the tractor up this morning to load it onto my trailer, it was kicking out the gray smoke screen again. Puzzled, I pulled the valve cover off, and sure enough, there was the pushrod out of its socket, and the rocker arm off kilter and partway off the rocker shaft. Here is what it looked like: Pictures by International284 - Photobucket

I checked the pushrod and it was still straight. I reassembled everything and checked the valve clearance, which was still spot-on. I tightened it up slightly and that seemed to reduce the side-to side play. (My clearance is now about 0.0045) 10 start and shutdown sequences later, everything was fine. When I started it this morning, I spun it up to build oil pressure and then released the decompression lever. I don't understand how using the decompression lever could make this happen; I don't want to mistake correlation for causation.

The ag tires from International 284 do not fit this tractor, the bolt circumference is different.

California, I had come to a similar idea as you: I tried using tow chains to make some improvised tire chains for use at the friend's flooded house. The principle would work, but, in this case, at least, what I needed was enough cross chains to connect my two circumferential towing chains. I didn't have enough other chain to keep the bands in place. In fact, I only have enough chain to do one side. It wouldn't have mattered.

The mud is so thick, and interspersed with rocks from softball to armchair size that this little tractor doesn't have a hope of cutting through it anyway. Even 4 wheel drive would have meant I could traverse the area better, not get anymore work done. I had my 6 foot box blade with added weights for ballast, so I had every chance I was going to. We got the driveway and road scraped free, but it is going to take a large tracked excavator to move enough yardage of mud. This little tractor just isn't enough, but it did what could be reasonably expected.

The turf tires, as anticipated, became totally mud-loaded and offered basically no traction. On the plus side, they also failed to dig deep enough holes to get stuck. I STRONGLY encourage anybody trying to improvise their own chains to use bolts through the chain or some other positive retention. Using tie wire around a chain hook to hold it was a necessary evil, and it worked, but one should find a better and safer way.

The inundated area is about 150 feet by 60 feet, and, near as we can tell, an average of 4 feet deep. Put another way, it's over 1300 cubic yards of material. The swimming pool is filled, and the interior of the house is starting to cave in from the pressure outside the walls.

It's really a tragedy, but we got enough of a pathway cleared that the family can go in and start collecting their possessions.

Thanks again for the assistance. Any ideas on why the pushrod keeps falling out when the clearances measure to specification?
 
   / YM240 smokes heavily, lacks power #34  
The compression release may not be adjusted right. Here is what the manual says on my YM1900:

1) Set the decompression lever at engine-operating position.

2) Set the piston at TDC as the inlet and exhaust valves are closed.

3) Loosen the adjusting screw of the decompression lever shaft.

4) Turn the adjusting screw clockwise until the tip of it touches the exhaust valve arm.

5) Then turn the adjusting screw again 360degrees and lock it by the lock nut. (The amount of decompression lift at this time will be about 0.0314 in. (0.8mm)

6) Repeat the same adjusting for the other cylinder.
 
   / YM240 smokes heavily, lacks power #35  
Sounds like your going the extra mile trying to help some folks out. My hat off to you again. As far as the push rod coming out, since the push rod is not bent my little simple mind concludes there had to be slack at some point in the up/down stroke in order for it to get out. That being said, I believe your valve is sticking open long enough for the push rod to come out before the piston knocks it back up. How's that for speculation? Next time you take the rocker arm cover off manually push that valve down and see if it tries sticking. You will have to roll that piston down to do it. After reading Gary's post I may be confused. Isn't that an intake valve that is throwing the pushrod?
 
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   / YM240 smokes heavily, lacks power #36  
I was thinking to wrap tow chains across the tread then through the gap between the the rim and the disc. Then up around the tread again and into the next adjacent gap. etc. The tread might slip a quarter turn (slowly!) before it catches traction again but since this is a real emergency, that's better than not using the tractor at all. This assumes you have enough tow chains, cables, old tire chains, whatever to wrap both tires.

If you can get that thing started I wouldn't worry about testing compression for now.

As for the pushrod - Looking at your picture the rocker/shaft assembly looks intact. So maybe a valve stuck open for a moment and let the pushrod fall out after the cam turned and that lifter went back down. Does that valve spring seem to have normal strength? Maybe watch the valve gear while making a cold start??? Maybe oil the valve guide from above with an oilcan? This is the first time I've seen a post here on this subject so that problem must be rare.

One other possibility occurred to me: Yanmar defines #1 cylinder as nearest the flywheel, NOT the cylinder nearest the radiator. And the two cylinders fire 180 degrees apart. (then nothing for another 540 degrees of crank rotation). So - could you be adjusting that valve to .006 at some point other than TDC? That could leave huge slack in the valve train, enough to let the pushrod fall out.
 
   / YM240 smokes heavily, lacks power #37  
California, do you have a YM240 parts manual handy? I don't see anything in his picture to hold the rocker arms on the towers, (he mentions side play), as in item 28 . The YM1500 uses washers and screws to do the job.
 
   / YM240 smokes heavily, lacks power #38  
From the head shot of the valve train, it looks to me like the offending valve adjuster is backed out quite a bit more than the other 3. (Like 1 full turn at least). Is that so? If it is, why would the arm need to be adjusted like that, or did it loosen up during break-in ? Is it possible that the push rod is not seating on the lifter properly or is the rocker arm seat messed up and the tappet slips out after a few cycles...
 
   / YM240 smokes heavily, lacks power #39  
California, do you have a YM240 parts manual handy? I don't see anything in his picture to hold the rocker arms on the towers, (he mentions side play), as in item 28 . The YM1500 uses washers and screws to do the job.

Unless he has taken them off for the photo they are missing and they hold the rocker arms on the shaft. They are called "set plates". If they are missing, I'm surprised the other arms stayed in place.

Notice the shiny 1/3 arch on the rocker arm? That is where the set plate rubbed the arm.
 
   / YM240 smokes heavily, lacks power #40  
you can try this when my tractor starts to smoke i pour a quirt of tranny fluid in the fuel -----and to salve the next problem get a infrared thermometer and point it at the manifold this will tell if one cylinder is firing or not fast and cheap fix the oil will give you more power to :thumbsup:
 

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