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Discussion Starter #1
Hi all, got this Massey Harris 33 gas about a month ago and am doing work on it. Has many issues as expected, wasn't very well maintained.

But here's the one I'm focusing on right now, doesn't make sense to me. Did a compression test, not exactly by the manual, just wanted to get an idea what I'm dealing with, so the engine is cold, the air filter not removed, and the throttle not wide open, so lower compression numbers I expected. What I didn't expect was this, on cylinder number 2:


I've done my share of compression tests and I never had this happen before; the dial goes fairly quickly back to zero after reaching max compression. This happens only on cylinder number 2. The test on the other three cylinders went as expected, dial goes to max value when cranking a few times and then stays there.

Any ideas why this might be happening?
 

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Put a couple tablespoons of oil in the cylinder and see what happens. If the compression stays up the rings are bad.
 

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Discussion Starter #4
Yes, this was a dry test. I will do another test, dry and wet, with WOT, air cleaner off, and spark plugs out, as per the manual. As is, all cylinders show around 90 psi, where the manual says 110-120.

Wish it was warmer out to do a valve adjustment as well. But last Saturday was 7F/-14C... not the greatest to work on an engine.
 

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Am I missing something..?? Did you test other cylinders after checking #2..?? In my mind, seems like the check valve in the tester isn't closing off, holding the psi of max. compression. Depending on where the engine stops, thinking there is a good chance one of the valves is open slightly, allowing you to lose the compression.

Seems like a leak down test would work better. Set each piston at TDC, then attach a similar hose connection, with regulated air, and listen for leaks, unless you have a specific leak down tester gauge.

You could use your compression tester hose, if you remove the schrader/check valve.
 

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Discussion Starter #7
Sorry about the confusion, let me describe the test I've done better.

Am I missing something..?? Did you test other cylinders after checking #2..?? In my mind, seems like the check valve in the tester isn't closing off, holding the psi of max. compression.
Yes, I tested the cylinders in order. #1 held max pressure. #2 didn't, and in fact the dial went to zero very fast. This was with the spark plug of #1 out. Then I put the spark plug on #1 back in, tight as per specs. Re-tested #2, and that's the video I posted, with the dial going to zero but slower than when the plug of #1 was out. Then I tested #3, gauge holds max pressure. Then #4, same as #3, holds max pressure.

I was aware of the fact that the schrader valve on the tester might cause this problem, but it only happens to #2, and by the way, it never happened before with this particular tester, so I was inclined to trust the valve.

However, I gave it some more thought. The whole principle of the compression test is that only temporarily there is high pressure in the cylinder, on the compression stroke when the valves are closed. That pressure opens up the schrader valve of the tester, and said valve keeps the pressure on the other side of it, in the gauge and tube. I don't know why I thought that the pressure is kept high in the cylinder, IT IS NOT. So it must be the tester that failed only on cylinder #2

Depending on where the engine stops, thinking there is a good chance one of the valves is open slightly, allowing you to lose the compression.
This may be true, but the pressure did build up to 90 psi in the gauge.

Seems like a leak down test would work better. Set each piston at TDC, then attach a similar hose connection, with regulated air, and listen for leaks, unless you have a specific leak down tester gauge.
Don't have the necessary fitting to do a leak down test.

You could use your compression tester hose, if you remove the schrader/check valve.
I will remove it, and clean it, and redo the test a few times.

Your reply really helped me, made me give it more thought and I think I know what's happening now.

Now I must think if 90 psi is ok or too low for this Continental E201 engine. Spec says it should be 110-120 :/


Sorry about the confusion, let me describe the test I've done better.
 

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No problem. It wouldn't be that hard to make a leak tester, rather than a leak down tester. If you have an old spark plug, you could knock the porcelain and electrode out of it. Clip the "L" portion of the electrode off, then if you have a torch to do it, braze/gas weld a 1/4" pipe sleeve on it. Attach a quick connect fittings, with male threads. Hook your shop air hose up to it, with a low psi,and gradually increase pressure with the regulator, and listen for leaks, with piston at TDC.

Just be sure to remove the hand crank, if you're using one. Too much pressure may push the piston down, and send the hand crank flying. You could put it in gear, and set the brakes to keep the engine from rotating. Might want to loosen the radiator cap too, in case it's a blown head gasket. But that may show up, or be suspicion if the spark plug looked pretty nasty.

I made a similar set up years ago, to force penetrate down around the stuck pistons & rings on an old McCormick-Deering O4 orchard tractor. Removed the valve train, poured what penetrate would go in a cylinder, screwed in the adapter, and hooked a portable air tank up to it with 100 psi, and walked away for a couple hours. I'd taken the drain plug out of the oil pan, and set a drain pan underneath to catch anything that may be going down around the pistons. After a few hours, I was getting some drips. Just kept refilling, and putting the air back to it. On the second day, I was getting a pretty decent trickle. Did that with all 4 cylinders, then took an oak block, and 4 lb. sledge, and drove the pistons out fairly easy, when I finally got the engine in the shop, to tear it down.
 

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Discussion Starter #9
Neat idea about the leak tester DJ54. I have an acetylene/air torch and can do brazing. Will look for parts. Not sure I understand the difference between a leak down and a leak test.

I'm also looking now for a better compression tester.
 

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What I've seen,and as I understand, a leak tester will tell you what percentage of compression you're losing. A leak test just tells you where it's leaking. Down around the piston rings, out past a valve, or, into the cooling system, whether from a blown head gasket, or cracked head.

Just seems a lot simpler, if you don't have good compression, put the air to it, and see where the compression is being lost.
 

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Discussion Starter #11
Guys, mystery solved!

Got another compression tester. With throttle wide open and air cleaner removed, different results.
Cyl 1 120
Cyl 2 118
Cyl 3 110
Cyl 4 100



The problem was, as I thought, the scrader valve on the other tester.

Quite a difference between cylinder 1 and 4 though. How much should I worry about this?
 

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It may be the perfect time to make that adapter to put air pressure on #4 cylinder. It may just be an exhaust valve burned a bit, letting compression escape, and lapping the valve in would be a pretty easy fix.

I was taught it's better to have an exhaust valve a smidge loose (couple of thousandth's), than tight, holding it open a bit, causing it to burn.
 

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Discussion Starter #15
It may be the perfect time to make that adapter to put air pressure on #4 cylinder. It may just be an exhaust valve burned a bit, letting compression escape, and lapping the valve in would be a pretty easy fix.
Thank God the compression kit that I got (used) includes an air compressor adapter! But, guess what. The wet test on cyl #4 was 125 psi.

I was taught it's better to have an exhaust valve a smidge loose (couple of thousandth's), than tight, holding it open a bit, causing it to burn.
The tractor really needs the valves adjusted, as who knows when they were last done.

Question for you guys: manual says 14 thou for valve clearance with engine warm. Would it be safe to set it to 16 thou cold?
 

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Discussion Starter #16 (Edited)
Maybe a difference but the percentage is still in the acceptable 20% range.
Are you sure about this? I thought the acceptable difference is 10%.

However, my plan for this tractor is to use it only for the loader, move some soil or snow, nothing really heavy duty ground engaging. Would be happy to have it run smoothly and with clean fluids.
 

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Thank God the compression kit that I got (used) includes an air compressor adapter! But, guess what. The wet test on cyl #4 was 125 psi.



The tractor really needs the valves adjusted, as who knows when they were last done.

Question for you guys: manual says 14 thou for valve clearance with engine warm. Would it be safe to set it to 16 thou cold?
I just checked my I&T manual for my IH tractors. It must be in the OEM book out in the shop that gives setting both hot, and cold. I can't remember what the difference is, between setting cold & hot.

Personally, I set mine after warming it up, at a slow idle. There is definitely a knack to it, but, I know they are on the money.
 

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Discussion Starter #18
Checked my Massey Harris manuals, only hot values mentioned.

The reason why I'd do it cold is because there was a wheat berry size hole in the sediment bowl assembly and gas was dripping. Drove me nuts. So "smart" proceeds to braze it with some metal solder. Well, it suddenly melted :/ maaaan!

So now I'm waiting for a replacement from fleabay. Since we're on the subject, all replacement sediment bowl assemblies say the thread that goes up to the tank is 3/8. My old one is more like 5/8 . Can't find specs for the original anywhere. And sediment bowl assemblies with larger than 3/8 thread are unobtainium.











 
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