Valve lash adjust on two cylinder models?

[California]

Quick summary of this longwinded post: Is there some way to find TDC by watching the rockers on the alternate cylinder? This two-cylinder fires 180 degrees apart. So the timing mark on the front pulley doesn't reflect what the #2 cylinder is doing. The timing mark for cylinder #1 is barely visible down through the clutter and impossible to see when the pulley is turned another half revolution. So I set valve lash at whatever crank revolution that the .006 gauge would slide in. Ok?

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It's been 20 years ownership, but only 400 hours, since I bought the YM240 (1980 model) and went through everything at that time. At about year 10 I bought a second tractor and since then have hardly used this one.

I got to thinking about Periodic Maintenance when I looked at the tag I had on the radiator, 'coolant replaced 2009'. I've done air filter replacement and oil changes timely but not much else. Replaced the UTF initially (dirty!) and again at the 10 year point (looked like new).

Yesterday I checked the battery water for the first time in a couple of years and found it barely above the plates. Ok, it's time to treat this elderly tractor more kindly. Since I use the little YM186D far more that this YM240, I realize I've been neglecting this one.

I re-torqued the head. 5 of 6 bolts wouldn't budge but one turned 45 degrees. Looks like I averted a problem there.

Valve lash: All were too tight at what I figured was TDC, firing position. But I was able to find a point somewhere in the crank rotation where the .006 gauge would go through, not a .008, so I left those alone and adjusted the others to where the gauge would go through at some point in the cycle. Maybe just my imagination but starting and low idle seem nicer now. It just purrs.

Is finding the spec valve clearance at some random point in the cycle, a bad practice?

 

[winston1]

I agree with Aarons method, at least on these old Yanmars. Easiest way to set the valves on your Yanmar

 

[California]

I agree with Aarons method, at least on these old Yanmars. Easiest way to set the valves on your Yanmar

Thanks Winston. That makes sense, I've used that method before on other engines.

I tried to do that here but couldn't see Aaron's "when the valve is in the middle of that stopped position at the top". The rocker motion is so slight (.006") that there's nothing visible. Pushrod slack, and whenever gauge would go in, was all I could use to judge if I was getting the spec valve clearance. It felt like that was the middle of the cycle Aaron described.

But in theory this assumes the cam is perfectly round except at the lobes. Maybe I'm overthinking this.

 

[bmaverick]

Quick summary of this longwinded post: Is there some way to find TDC by watching the rockers on the alternate cylinder? This two-cylinder fires 180 degrees apart. So the timing mark on the front pulley doesn't reflect what the #2 cylinder is doing. The timing mark for cylinder #1 is barely visible down through the clutter and impossible to see when the pulley is turned another half revolution. So I set valve lash at whatever crank revolution that the .006 gauge would slide in. Ok?

-------
It's been 20 years ownership, but only 400 hours, since I bought the YM240 (1980 model) and went through everything at that time. At about year 10 I bought a second tractor and since then have hardly used this one.

I got to thinking about Periodic Maintenance when I looked at the tag I had on the radiator, 'coolant replaced 2009'. I've done air filter replacement and oil changes timely but not much else. Replaced the UTF initially (dirty!) and again at the 10 year point (looked like new).

Yesterday I checked the battery water for the first time in a couple of years and found it barely above the plates. Ok, it's time to treat this elderly tractor more kindly. Since I use the little YM186D far more that this YM240, I realize I've been neglecting this one.

I re-torqued the head. 5 of 6 bolts wouldn't budge but one turned 45 degrees. Looks like I averted a problem there.

Valve lash: All were too tight at what I figured was TDC, firing position. But I was able to find a point somewhere in the crank rotation where the .006 gauge would go through, not a .008, so I left those alone and adjusted the others to where the gauge would go through at some point in the cycle. Maybe just my imagination but starting and low idle seem nicer now. It just purrs.

Is finding the spec valve clearance at some random point in the cycle, a bad practice?

This is all the YTOG has for a service manual for the YM240.

 

[California]

This is all the YTOG has for a service manual for the YM240.

Thanks.

That's the 4x4 supplement to the Service Manual.

I have the YM240 Service Manual hard copy, but all it says is do #1 cylinder at its TDC mark (did that) then turn the crank precisely 180 degrees to set #2. This is impossible when there's too much in the way to see the mark after rotating it, and the pulley is impossible to rotate precisely when holding tension on the fan belt and pulling on the fan. That's why I got to very roughly 180 degrees, then found where the feeler gauge slid in most easily. Then wondered later if that was accurate.

Also have the I&T Service Manual for Yanmar, it says the same thing, rotate precisely 180 degrees for #2.

 

[bmaverick]

Also have the I&T Service Manual for Yanmar, it says the same thing, rotate precisely 180 degrees for #2.

I only have the first few pages of the I&T SM. You are the first person to ever mention having a full manual. I guessed it was out of print as nobody ever made mention of it.

 

[California]

I only have the first few pages of the I&T SM. You are the first person to ever mention having a full manual. I guessed it was out of print as nobody ever made mention of it.

The I&T Yanmar [condensed] Shop Manual is limited to pre-1980 models. I see it on Ebay continually. But today those are likely reprints. Some guy in UK lists what seem to be new originals.
Look among Ebay search results for 'Yanmar Shop Manual'.

NEW SPIRAL BOUND YANMAR TRACTOR YM135 YM155 YM195 YM240 YM330 & D SERVICE MANUAL | eBay

THIS IS A NICE SPIRAL BOUND EASY TO READ DETAILED SERVICE MANUAL.

www.ebay.com

A google search finds several tractor dealers offering it.

https://www.google.com/search?&q=I%26T+shop+manual+YM-1

Amazon says NLA.

 

[rScotty]

Old mechanics all use the same method for setting Valve clearance. Here is the how and why of it.

Setting the clearance on the valves on any engine can be done using the same simple method and without the necessity of hunting for TDC & compression strokes. The only things necessary is that the valve cover be off so you can watch the rockers, and that you are able to manually turn the engine in the normal direction of rotation.

On any engine, we want to avoid mistakes, so we adjust the valves one cylinder at a time.

First, figure out which cylinder you want to start with, and identify the intake valve and exhaust valve for that cylinder.
Now rotate the engine in the normal running direction until the exhaust valve is just beginning to open. You can find this point easily by feel or eyeball. It doesn't have to be exact, just close.

Now think about what is happening in that cylinder when the engine is running. The point when the exhaust valve is just STARTING to OPEN is when the flaming hot exhaust gasses are at their highest temperature and pressure. We know that the exhaust valve is about to fully open up and push those flaming gases out the exhaust pipe - and we know for sure that this is the one time we can guarantee that the intake valve must be must be fully closed. It isn't a critical measurement. A few degrees one way or the other won't matter, because no engine designer wants to take a chance on flaming exhaust gases being pushed back into the intake. So we know that this is the best place to adjust the INTAKE valve clearance on any engine.
Therefore:
1. Chose any cylinder, and YOU SHOULD ADJUST THE INTAKE VALVE CLEARANCE WHEN THE EXHAUST VALVE IS JUST BEGINNING TO OPEN.

Now to set the exhaust valve clearance on that same cylinder, we will rotate the engine a bit farther until we watch the INTAKE valve open and then close. Just a few degrees after the valve has finished fully closing is where we will SET THE EXHAUST valve clearance. Again, a few degrees one way or the other won't matter.
We know that inside the engine this is the point at which the piston has begin to rise up into the head to compress the new charge that is to be burned. We also know that for any engine, this is the point in its cycle when the exhaust valve will be fully closed. Nobody wants raw unburned gases being forced into the hot exhaust pipe.
Therefore:
2. On that same cylinder as before, YOU SHOULD ADJUST THE EXHAUST VALVE CLEARANCE WHEN THE INTAKE VALVE HAS JUST COMPLETELY FINISHED CLOSING.

Once you think it through and get the picture of what is happening inside the engine, you will never have to search around for those elusive pulley TDC markings or wonder if it is on the correct stroke.

BTW, when I measure the existing clearance and it is within a ,001 of an inch of the desired setting I don't reset them. IMHO, you will wear out the adjusters trying to chase that .001 of an inch, and accomplish nothing because the adjuster will relax into its familiar clearance almost immediately when the engine starts. So that brings up the question of, "Just how close is close?" If you can ignore .001, where is the limit? For me the limit is in the direction of the clearance. If it is .002" loose, I let it be. If it is .002 too tight I will set it.

Enjoy,
rScotty

 

[California]

... ADJUST THE INTAKE VALVE CLEARANCE WHEN THE EXHAUST VALVE IS JUST BEGINNING TO OPEN.
... ADJUST THE EXHAUST VALVE CLEARANCE WHEN THE INTAKE VALVE HAS JUST COMPLETELY FINISHED CLOSING.

Enjoy,
rScotty

THATs what I had forgotten!! Thanks!

I kept thinking there's a simpler way than what the Service Manual says. But I couldn't remember what it was. I then looked in the I&T manual. This isn't mentioned there either. Now nearly 80, I at times forget stuff I learned long ago. Covid didn't help.

Your description is what we did 50-60 years ago when I had old cars and bikes that needed tinkering. And probably did 20 years ago when I went all through the severely neglected YM240 after I bought it. It's obviously the best way to tackle unfamiliar equipment.

There was another helpful rule-of-thumb for SBC etc. Watch when an exhaust valve closes and an intake opens, and at that time adjust the cylinder that is just opposite it in firing order. But with these Yanmars not firing 360 degrees apart, that doesn't apply.

Related, 18436572 is still in my head 60 years after I last needed it.

Wife says she forgets stuff now because her brain reached capacity and can't hold more. Maybe that's real.