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- Thread starter Brad M-C
- Start date
ScottyHOMeY
Well-known Member
Fill???? It shouldn't take more than a tablespoon or so per culinderImproved compression with oil on top of the pistons indicates worn rings. The oil provides a temporary seal. Still rings in a 123 that would produce 150# with a little oil on top should be showing you some compression dry.
You may also have valve issues if the engine is that badly worn, but the fact that you were able to build 150# I wouldn't expect a serious valve problem.
Just from your description, I'm a little worried about your test method. How much oil did you actually put into each cylinder?
You may also have valve issues if the engine is that badly worn, but the fact that you were able to build 150# I wouldn't expect a serious valve problem.
Just from your description, I'm a little worried about your test method. How much oil did you actually put into each cylinder?
It would make sense that he is FILLING the cylinders with oil.
A tablespooon of oil in each cylinder would not bring the compression up to 150PSI from ZERO. Not in a million years.
The only way you'd get that much improvement is if you FILL the cylinders with oil. Even if a valve is stuck open on each cylinder, the oil pumping out would create a good amount of pressure for one revolution.
I gotta wonder how much oil blows out the exhaust. It must make a HUGE mess.
A tablespooon of oil in each cylinder would not bring the compression up to 150PSI from ZERO. Not in a million years.
The only way you'd get that much improvement is if you FILL the cylinders with oil. Even if a valve is stuck open on each cylinder, the oil pumping out would create a good amount of pressure for one revolution.
I gotta wonder how much oil blows out the exhaust. It must make a HUGE mess.
LOL... A tablespoon makes no difference on the compression. When I say fill I mean as much as they will hold. At first I thought that my compression tester was broken, but I checked it on my lawnmower and it reads fine. Logic dictates that if it had a ring problem it would not be reading zero across all cylinders; that i would be getting at least a poor reading off of some. The oil cannot push out the valves as easily as air can so I get a reading when I am testing the pressure in oil.
ScottyHOMeY
Well-known Member
In that case, start with your valves. Just for giggles, just do an eyeball check of your ignition rotor relative to the position of your pistons. It would be durned unusual, too, even if the head were left to rust full of rainwater, for the valves to have stuck with one open on every cylinder. I'm startin' to suspect somethin' along the lines of a bad cam gear/valve timing. Can't rule out somebody in the past havin' a pull-the-tractor-pop-the-clutch party to get a stuck motor free, either. That can bust rings in a hurry.
Get your valve cover off and watch while it cranks and see what you've got there.
Get your valve cover off and watch while it cranks and see what you've got there.
ScottyHOMeY
Well-known Member
*grinning*
It's hard to get a valve stuck open on each cylinder as only two of the fours strokes need an open valve. Kinda like havin' nothin' for rings on all four at once.
There's somethin' else goin' on there. I'm kindsa suspecting he could also have a jumped/stripped out/gaptoothed cam gear or that it got reassembled without timing up the cam gear correctly. Who knows, maybe he's hydrolocked and cracked the pistons by crankin' on em when they're full of oil. (jk)
He won't have to crank too many cylinders full of oil through to fill up either the exhaust or the intake side of the head, depending which valves, if any are stuck. If he is pumpin' the oil up into the head, I believe I'd be gettin the manifold or at the least the carb off of it. Pump enough in there and it'll be bubblin' over the top of the exhaust or startin' to fill up the air cleaner or both!
Brad! What if any work has been done on the tractor lately?
It's hard to get a valve stuck open on each cylinder as only two of the fours strokes need an open valve. Kinda like havin' nothin' for rings on all four at once.
There's somethin' else goin' on there. I'm kindsa suspecting he could also have a jumped/stripped out/gaptoothed cam gear or that it got reassembled without timing up the cam gear correctly. Who knows, maybe he's hydrolocked and cracked the pistons by crankin' on em when they're full of oil. (jk)
He won't have to crank too many cylinders full of oil through to fill up either the exhaust or the intake side of the head, depending which valves, if any are stuck. If he is pumpin' the oil up into the head, I believe I'd be gettin the manifold or at the least the carb off of it. Pump enough in there and it'll be bubblin' over the top of the exhaust or startin' to fill up the air cleaner or both!
Brad! What if any work has been done on the tractor lately?
Rotor lines up with compression stroke on each cylinder. How do I check the valve timing? The rocker is moving every valve open and closed right now with plenty of clearence once closed. If I take the rocker assembly off so none of the valves open and I don't have a ring problem I should have compression...Right?
ScottyHOMeY
Well-known Member
To your last question, Right? is right.
I asked in my post up above to mkirsch, but you may not have seen it yet. Do you know the history of the machine? Has there been any work done to the tractor lately? It's shapin' up like something is busted pretty badly or something isn't put back together correctly.
If you can see each valve stem moving when the rocker arm bears down on it, you should be finding some compression somewhere even with just a little oil per cylinder on the test. You could have one or two two valves stuck and not popping up completely, but if the motor was left to get stuck, it whould be two valves at most. At any given time in a four-cycle, four cylinder motor, there are only two valves open at any one time -- one for exhaust, one for intake. both valves on the other two cylinders are closed up on either combustion or compression. (the design of the cam make make that not QUITE true, but it's a good rule of thumb that the motor will stop in a position like a describe.
I asked in my post up above to mkirsch, but you may not have seen it yet. Do you know the history of the machine? Has there been any work done to the tractor lately? It's shapin' up like something is busted pretty badly or something isn't put back together correctly.
If you can see each valve stem moving when the rocker arm bears down on it, you should be finding some compression somewhere even with just a little oil per cylinder on the test. You could have one or two two valves stuck and not popping up completely, but if the motor was left to get stuck, it whould be two valves at most. At any given time in a four-cycle, four cylinder motor, there are only two valves open at any one time -- one for exhaust, one for intake. both valves on the other two cylinders are closed up on either combustion or compression. (the design of the cam make make that not QUITE true, but it's a good rule of thumb that the motor will stop in a position like a describe.
Too Far Gone
Member
Pull valve cover and turn it over.If all valves are moving, OK,iF NOT,It may be cam gear.The center busted out on my 400 and it had no compression and turned over way too fast
ScottyHOMeY
Well-known Member
Valve timing . . .
The only sure way is to open up the timing cover and check for correct alignment of the marks on your gear teeth (crank to cam) and make sure they're right, and check the condition of the gears and teeth. Getting in there is a lot of work. If you do, check the timing and condistion of your governor gear at the same time.
Easier and, for the moment, adequate, is to watch your pistons and valves as you turn the motor by hand. Your valves, from front to back are EI-IE-EI-IE. You should see the intake valve on #1 open and close. As you turn from there you should feel compression at the plug hole. Keep turning through what would then be the combustion stroke, and at just about the time that the exhaust valve starts to open, you should be able to see #2 piston very near the top of it's stroke. This is all eyeball, there's nothing precise about it, but if it's that close, the valves are not so far out of time that you shouldn't be able to get some compression somewhere.
The only sure way is to open up the timing cover and check for correct alignment of the marks on your gear teeth (crank to cam) and make sure they're right, and check the condition of the gears and teeth. Getting in there is a lot of work. If you do, check the timing and condistion of your governor gear at the same time.
Easier and, for the moment, adequate, is to watch your pistons and valves as you turn the motor by hand. Your valves, from front to back are EI-IE-EI-IE. You should see the intake valve on #1 open and close. As you turn from there you should feel compression at the plug hole. Keep turning through what would then be the combustion stroke, and at just about the time that the exhaust valve starts to open, you should be able to see #2 piston very near the top of it's stroke. This is all eyeball, there's nothing precise about it, but if it's that close, the valves are not so far out of time that you shouldn't be able to get some compression somewhere.
I pulled the rocker assembly and ran compression again and still get zero on all cylinders, even with a little oil. I can pump air into the cylinder with an air pump and the motor will not turn over, but i cannot hear where the air is comming back out at. Can the rings be checked without pulling the piston?
ScottyHOMeY
Well-known Member
"Can the rings be checked without pulling the piston?"
If you've got a good ear and an airhose, you can try, one cylinder at a time. Hook whatever you're using to put air into the cylinders up. Best is a hose from a compressor with the tank pressure up and the power off. Set your regulator at 100# or so and put the air in and listen. Turn the motor one cylinder at a time and test the one where both valves appear to be closed. (If the rocker is off, they should all be closed, if not, closed vlaves are indicated by a gap between the rocker face and valve stem). If you get a sound of escaping air from the exhaust pipe on top of the manifold, there's an exhaust valve stuck open on that cylinder. If you have air leaking back out through the carb (it helps to remove the hose between the air cleaner and carb, it's an intake valve stuck. You might have to drop the pan to hear it, but if the sound seems to be coming from the bottom of the motor, you can suspect your rings. If you've still got a lot of oil in your cylinders, you may hear a drip in the pan instead of an air leak, as the oil is forced out. If it bubbles or hisses out through your radiator, think head gasket.
If you've got a good ear and an airhose, you can try, one cylinder at a time. Hook whatever you're using to put air into the cylinders up. Best is a hose from a compressor with the tank pressure up and the power off. Set your regulator at 100# or so and put the air in and listen. Turn the motor one cylinder at a time and test the one where both valves appear to be closed. (If the rocker is off, they should all be closed, if not, closed vlaves are indicated by a gap between the rocker face and valve stem). If you get a sound of escaping air from the exhaust pipe on top of the manifold, there's an exhaust valve stuck open on that cylinder. If you have air leaking back out through the carb (it helps to remove the hose between the air cleaner and carb, it's an intake valve stuck. You might have to drop the pan to hear it, but if the sound seems to be coming from the bottom of the motor, you can suspect your rings. If you've still got a lot of oil in your cylinders, you may hear a drip in the pan instead of an air leak, as the oil is forced out. If it bubbles or hisses out through your radiator, think head gasket.
As far as history goes. It had a bad head gasket and two stuck cylinders. I took the head off and soaked the pistons in in atf for about 6 weeks. They started to move, but would not make a full rotation so I got a hone and honed the two cylinders that were sticking. Put it back together yesterday and that is where I am at. The guy I bought it off of said he did try to pull it with a truck a few times to free the motor up. I have suction at the carb.
Brownie 450
Member
Since valve timing is close, & other things like rings can't be checked without disassembly, try putting a socket on a few of the head bolts to see if they are tight. I'm wondering if you might have a head gasket problem. Can you hear compression leaking away anyplace in the head gasket area? Outside of rings or a head gasket, about the only other thing is holes in the pistons??? Maybe completely shot valves??
ScottyHOMeY
Well-known Member
If you have vacuum, you should have compression, but if it's weak, it may not be enough compression to register on your gauge if there's another problem.
I'm assuming you've got a new head gasket on it. Is it torqued down properly? Someone else mentioned it up above and I should have included it on my list of things to listen for when you do the pressure test on each cylinder -- a bad head gasket will leak around the edges, can bubble up through the radiator as I described, or can pop out through to an open valve on an adjacent cylinder and seem to be an open valve on the other cylinder.
As long as you didn't get carried away with the honing, you won't have done any damage that way. Shouldn't usually take for than a few strokes up and down with the hone to checker the cylinder walls.
Do you have new rings on it? If not, did you clean up the old ones and the grooves they ride in thouroughly? Do they move freely? Did you stagger them so that the gaps on the rings are distributed fairly evenly around the piton and lot all in a row.? Rings on stuck pistons tend to be stuck in place as well and difficult to salvage, and if things are loose enough to go back together without you loosening the rings up and then using a ring compressor to get them back in, they may in fact be loose enough to keep you from getting any compression.
I'm assuming you've got a new head gasket on it. Is it torqued down properly? Someone else mentioned it up above and I should have included it on my list of things to listen for when you do the pressure test on each cylinder -- a bad head gasket will leak around the edges, can bubble up through the radiator as I described, or can pop out through to an open valve on an adjacent cylinder and seem to be an open valve on the other cylinder.
As long as you didn't get carried away with the honing, you won't have done any damage that way. Shouldn't usually take for than a few strokes up and down with the hone to checker the cylinder walls.
Do you have new rings on it? If not, did you clean up the old ones and the grooves they ride in thouroughly? Do they move freely? Did you stagger them so that the gaps on the rings are distributed fairly evenly around the piton and lot all in a row.? Rings on stuck pistons tend to be stuck in place as well and difficult to salvage, and if things are loose enough to go back together without you loosening the rings up and then using a ring compressor to get them back in, they may in fact be loose enough to keep you from getting any compression.
gene bender
Well-known Member
What do you mean you pulled the rocker assy and had no compression. You dont pull the rocker assy off.
gene bender
Well-known Member
You dont fill with oil. Time for you to start over. Remove all plugs replace the rocker assy and set valves for clearence. Now when the engine turns over make sure all have some movement. Now you will get a reading on each cyclinder. How high a reading is not important just get a reading. If all pushrods move up and down and the tappets are set to tolerence you will have compression. You can feel pressure as engine turns over. Check each cycl for pressure as the engine turns. You could have a broken crank if there is no pressure but valves could still open and close. let us know what happens now.
Dave from Texas
Member
I had a flat head 6 cyc in an old car that had the same problem. all of the valves were stuck open. Worked them by pushing and pulling them up several times and they finally started working correctly.
NawlensGator
Member
I don't think it's possible to have suction at the carb and then zero pressure in all cylinders. My 140's have 150 psi compression on all cylinders without using oil. Your missing something.
I had lower pressure once because the gauge fitting wasn't seating in the plug hole. Had to ream out (18 mm) the threaded hole and then I got pressure. I bet it's something real simple.
ScottyHOMeY
Well-known Member
I'm kinda with you and gene,Gator. It's gonna be a real mess or real simple, one or the other. Might be time for a breath and start over.
Try putting your thumb over the spark plug hole, or sticking whatever finger fits tightly into the hole, then hit the starter.
If it feels like it's trying to blow your finger out of the hole, or air gets pushed by, you have at least SOME compression.
You said the valves have "plenty" of clearance earlier. How much clearance? Factory clearance, or a lot of clearance, like 1/4"?
Where did all the oil go when you FILLED the cylinders with oil? Wherever that oil ended up is where it's leaking, if it's leaking.
Even if you had really bad rings and all the gaps lined up, you'd still have SOME compression, not zero.
Even if the valves weren't seating properly, you'd still have SOME compression, not zero.
In order to get zero compression,
#1. all four pistons would have to have large holes in them...
OR
#2. at least one valve in each cylinder would need to be stuck wide open.
If #1 were true, then you would never have been able to fill the cylinders with oil. All the oil would've run down into the crankcase before you could turn the engine over.
If #2 were true, then you woudn't have normal valve clearances in the head.
If it feels like it's trying to blow your finger out of the hole, or air gets pushed by, you have at least SOME compression.
You said the valves have "plenty" of clearance earlier. How much clearance? Factory clearance, or a lot of clearance, like 1/4"?
Where did all the oil go when you FILLED the cylinders with oil? Wherever that oil ended up is where it's leaking, if it's leaking.
Even if you had really bad rings and all the gaps lined up, you'd still have SOME compression, not zero.
Even if the valves weren't seating properly, you'd still have SOME compression, not zero.
In order to get zero compression,
#1. all four pistons would have to have large holes in them...
OR
#2. at least one valve in each cylinder would need to be stuck wide open.
If #1 were true, then you would never have been able to fill the cylinders with oil. All the oil would've run down into the crankcase before you could turn the engine over.
If #2 were true, then you woudn't have normal valve clearances in the head.
Hugh MacKay
Well-known Member
Brad: I've been following this thread, and have one of two opinions. Either you don't have a clue what your doing, or your feeding us a line of BS.
Well thanks for your honesty.
And thanks to everybody who had input that was useful.
I found some time to tinker on it some more and tried the hose trick. Basically the thing is leaking air everywhere, I can here it coming though the drain on the oil pan, I can hear it coming though the valve springs, out the exhaust and air intake. I think this tractor has sat with water in it a lot longer than the former owner let on. and may have had some problems prior to sitting and locking up. I think it is time to cut my losses and part this one out.
And thanks to everybody who had input that was useful.
I found some time to tinker on it some more and tried the hose trick. Basically the thing is leaking air everywhere, I can here it coming though the drain on the oil pan, I can hear it coming though the valve springs, out the exhaust and air intake. I think this tractor has sat with water in it a lot longer than the former owner let on. and may have had some problems prior to sitting and locking up. I think it is time to cut my losses and part this one out.
Well, Hugh, you have always had a knack for getting to the issue. HAW-HAW!(quoted from post at 14:36:31 08/19/09) Brad: I've been following this thread, and have one of two opinions. Either you don't have a clue what your doing, or your feeding us a line of BS.
mike
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