YM240 smokes heavily, lacks power

[California]

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 .

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). ... why would the arm need to be adjusted like that

Norm I'll find and scan that page after dinner. I think you found the problem.

zzvyb6 [???] I noticed that too and I think it is a clue. That's why I suggested the valve lash might have been set at other than tdc.

 

[normde2001]

Norm I'll find and scan that page after dinner. I think you found the problem.

zzvyb6 [???] I noticed that too and I think it is a clue. That's why I suggested the valve lash might have been set at other than tdc.

Setting solid lifter valves at TDC is not necessary. All you need is a closed valve, regardless of where the piston is.
http://www.hoyetractor.com/valve-set.htm

 

[California]

True. But there has to be a reason why that adjuster is at the end of its threads, as if the pushrod were too long. Measuring valve lash with the cam part way up its slope is the only reason I can think of to cause this.

Just found this in my notes:

"You measure clearance at a specific point in the rotation of the crankshaft. It is often quoted as being a top dead center on the compression stroke, but rather than find top dead center for each cylinder - a hassle - you can check the intake for each cylinder when that cylinder's exhaust valve is just opening...and check the exhaust valve for that cylinder when it's intake valve has just closed. Doing it that way measures at the point of maximum critical clearance and avoids any confusion about valve overlap. Measured that way, the clearance should be the same as on TDC on the compression stroke."​

 

[winston1]

I can't tell that much difference on the threads showing on the valve adjusting screws. Looks to me like they are pretty close to the same. I'm probably not seeing it correctly. Even if there were room for a little extra slack because of the cam not being true on all the release time I don't believe it would be possible to be enough difference to allow a push rod to escape.

 

[California]

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 .

My YM240 parts manual shows the identical diagram to the Hoye page you referenced so I didn't bother to copy it again.

Norm, you are right. The "Diagram 3 item 28 #124450-11290 - Retainer, rocker arm 2 pcs" shown in the YM240 Parts Manual (and Hoye's web page) are missing in 284's photo.

 

[California]

'284', I see something else unrelated in that photo of the rockers.

See that cylinder head stud at left-front of the head that has extra threads sticking up? There should be a rod on there about 12 or 16" long that goes forward at a 45 degree angle to the left edge of the radiator, to support the radiator so it can't fall back into the fan. There would be a nut above the rod when it is in place.

Do you still have a box of mystery parts that came with the tractor? If so, post a photo and we'll try to figure it out.

 

[284 International]

Sorry it has taken me so long to respond. I don't have any other leftover parts, at least nothing that look like the "set plate" retainers in the diagram. I will fabricate or order something. I think this is the trouble, though. It seemed odd to me that there was nothing retaining the rocker arms. I should have done more research.

I tried setting the valve clearance a couple different times, and spinning the engine through to recheck, but I'll be more careful this time. I will count threads in the morning; that was a good catch noticing the difference (if any) in thread counts on the adjuster. I didn't even think to compare them.

Looking at Hoye's diagram, the pushrods and lifters are all interchangeable, so they aren't put into the wrong spot. Hopefully with the retainers on the rocker arms everything will be functional and keep things in line.

The valve springs feel light to me, but I don't have any medium of comparing them other than to modified passenger car or racing motorcycle valve springs. I can push them down some with a couple fingers. Is there a specification for spring rate on these? It sounds like I really am going to end up with a service manual....

California, I guess what you're saying is that I should have something better than a bungee cord holding the radiator away from the fan blades? :laughing: I actually have some steel stock I was planning to use to make something very like what you described. I'll get it fixed before I work it too much more.

Regarding the tire chain improvisation: The turf tire rims I have have very small gaps between the wheel hoop and the hub/wheel disk. ( I apologize for the motorcycle nomenclature, it's what I know.) I can't fit a fingertip between the gaps, so had no chance to fit my 3/8 chain through it. Basically I simulated a set of cable chains by wrapping a hoop of chain around the inside and the outside of the tire, and connecting them across the tire with chain crossbars. With a much longer chain than I have, a zig-zag pattern around and between the two hoops would have worked out ok, I think, but I didn't have enough chain to be really effective or safe.

Ultimately, for my intended uses, I need to get a proper set of ag tires and corresponding rims. Are the bolt patterns of these and anything else (Kubotas, Masseys, etc) compatible? The turf tires are hopeless trying to pull a disk or plow.

Thanks again for all the advice flowing in. It really is appreciated. I'll ask if the family minds me posting photographs of their home. I don't want to seem insensitive in posting their tragedies for the world to see without permission. The extent of how useful this little tractor will be to them in the immediate future is minimal, now, so I can get back to properly fixing it.

 

[California]

Somebody will be willing to trade you straight across, turf for ag tires, but it will take a while to find that person. Turf rims/tires are real expensive. Keep posting your intent here and on Craigslist.

My 2-piece rear wheels are Kubota rims on the original Yanmar discs and they fit perfectly. Not sure this is relevant to you. Kubota *might* have used the same bolt pattern as Yanmar where the disc meets the axle.

I see you have nearly finished resolving several issues that are nuisances but none of the issues look expensive. Congratulations! When it's complete you will have about half the cost into yours compared to mine and I thought mine was one of the cheapest Yanmars (with a loader) among the owners posting here. You did good.

 

[bowinelk]

I too have a 240 that i purchased with alot of untold stories. I have replaced the head and most of the top end. My valve cover is still off, here is a picture of what it should look like under there.
I sure do value this forum i have learned a ton here. I try to read here daily, It has helped keep my frustration at bay. I soon to will be trying to start mine again. waiting on new radiator. Keep us informed

 

[California]

I have replaced the head and most of the top end.

That's so clean and pretty! I wish mine looked new like that.

How does your valve spring tension compare to 284's? His 'pushed down with two fingers' sounds light. I thought it would be more like 'two thumbs, pushing hard' even if it is a low-rpm engine.