YM336D bad knocking engine

[murnere]

Computer?? What computer? I don't disagree with your thinking, because it certainly was running fine before the wash, but what computer is on this 1984ish YM336D?
I'm seriously asking, because one thing I like about this tractor is it seems so simple and I thought that was because it didn't have all the modern computers running it.

 

[CoyPatton]

Computer?? What computer? I don't disagree with your thinking, because it certainly was running fine before the wash, but what computer is on this 1984ish YM336D?
I'm seriously asking, because one thing I like about this tractor is it seems so simple and I thought that was because it didn't have all the modern computers running it.

IT DOES NOT!
All of your sending units are mechanical/electrical components.
NO ELECTRONIC ONES!! All you need on it to test any electrical issue is a 12volt test light.

Change of subject, but both valves being tight at the same time on that cylinder is a dead give away to your miss! Both loose is compression and fire strokes. Then you have 1 or the other loose/tight on intake (tight) stroke or exhaust (tight) stroke.
Check the gap on all 6 while it is apart. I have not looked this up so if I am wrong someone chime in (Winston) intakes are 0.006” gap and exhaust 0.008”

 

[murnere]

You are correct. The little yellow sticker was still on my valve cover and it says .006" when cool. By you saying it's a dead give away, do you mean that one of the valves is obviously too tight because you should never have both open (tight) at the same time? Or is this indicative of something bigger?
And I really do appreciate everyone who has chimed in. It sucks for you all that I'm learning this as I go, but I will learn this and pass it on when others need help.

 

[winston1]

Intake and exhaust .006".

 

[clemsonfor]

you said it started knocking AFTER you washed it, that points to water getting into the computer, there's nothing mechanical that would be affected by a wash..

There is NO computer on this tractor. It's ALL MECHANICAL!!:confused3::laughing::thumbsup:

 

[CoyPatton]

Intake and exhaust .006".

Thanks Winston!

 

[CoyPatton]

You are correct. The little yellow sticker was still on my valve cover and it says .006" when cool. By you saying it's a dead give away, do you mean that one of the valves is obviously too tight because you should never have both open (tight) at the same time? Or is this indicative of something bigger?
And I really do appreciate everyone who has chimed in. It sucks for you all that I'm learning this as I go, but I will learn this and pass it on when others need help.

If both valves are tight at the same time, both are open to the cylinder at the same time. This is a condition that should never happen if all is correctly set. There are 4 strokes: intake (intake valve open—rocker arm tight, exhaust closed—rocker arm loose-0.006”) compression both valves closed—rocker arms loose, fire both valves closed, exhaust (exhaust valve open—rocker arm tight, intake valve closed—rocker arm loose)
When I state rocker arm loose I mean that 0.006” clearance with the spring fully extended as assembled. It should wiggle slightly with your fingers.
Again I recommend doing all 6 valves while you have it apart.
With one cylinder remaining open at all times you have a misfire setup regardless of which stroke both valves are open on, likely 1 valve stays open on all 4 strokes.

 

[CoyPatton]

If both valves are tight at the same time, both are open to the cylinder at the same time. This is a condition that should never happen if all is correctly set. There are 4 strokes: intake (intake valve open—rocker arm tight, exhaust closed—rocker arm loose-0.006”) compression both valves closed—rocker arms loose, fire both valves closed, exhaust (exhaust valve open—rocker arm tight, intake valve closed—rocker arm loose)
When I state rocker arm loose I mean that 0.006” clearance with the spring fully extended as assembled. It should wiggle slightly with your fingers.
Again I recommend doing all 6 valves while you have it apart.
With one cylinder remaining open at all times you have a misfire setup regardless of which stroke both valves are open on, likely 1 valve stays open on all 4 strokes.

Hopefully, the out of adjustment valves are not sufficiently so to cause greater troubles.
I have to confess my ignorance at this point, I do not know if these are an interference motor or not. An interference motor is one where a missed time valve (overly tightened rocker arm in this case) will result in the piston head and valve contacting one another. Many things can happen in this situation:bent valve, hole in piston, broken valve,
Either of the last 2 could result in pieces of metal in the cylinder doing even more damage.
At this point, we know at least 1 valve is out of spec. Correct this problem and then see what the status is. It is a diesel so no easy way to look in the cylinder. A bore scope through the injector port is easiest, you have experience with the injector pulling. But I would adjust the valves (all 6) and go from there on how it runs.

 

[murnere]

Coy, great explanation. I understand the basics of the 4 stroke, but this put it into perspective for my particular problem. I have to get a deep well 17MM socket...I hope...to turn the engine over. It is very tight, but I think I'll be able to do it with a deep well. Thanks again.

 

[CoyPatton]

Coy, great explanation. I understand the basics of the 4 stroke, but this put it into perspective for my particular problem. I have to get a deep well 17MM socket...I hope...to turn the engine over. It is very tight, but I think I'll be able to do it with a deep well. Thanks again.

Good luck with and hopefully no damage from any contact with internal parts.