Does the 4B11T compression test strangely?
Mar 26, 2010, 08:50 AM
#17
If cyl 4 is the drivers side cylinder, doesnt that kinda rule out a lean condition (thus not causing higher than normal egts as a possible cause of ring failure) since its closest to the intake manifold opening? If cyl 4 is on the passenger side then it would make sense that that cylinder is running richer than the others by virtue of being further away from the intake manifold opening.
Last edited by MR. Tim; Mar 26, 2010 at 09:32 AM.
Mar 26, 2010, 09:04 AM
#18
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Not sure where you're going with that. If a cylinder is near the intake manifold opening, it'd have access to the most air, causing a leaner mixture... right?
With the way they design plenums, angles, etc... I don't think this is an issue. If anything, I would imagine that #4 is running hotter than the other 3 cylinders. But I could be wrong.
Lou
With the way they design plenums, angles, etc... I don't think this is an issue. If anything, I would imagine that #4 is running hotter than the other 3 cylinders. But I could be wrong.
Lou
Mar 26, 2010, 09:37 AM
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Ok.
Cylinder 1 is passenger side.
Cylinder 4 is driver side.
T/B opening is on driver side.
Cylinder 4 would get most air, correct? More air = leaner conditions, correct?
Just want to make sure I'm following you here...
Lou
Cylinder 1 is passenger side.
Cylinder 4 is driver side.
T/B opening is on driver side.
Cylinder 4 would get most air, correct? More air = leaner conditions, correct?
Just want to make sure I'm following you here...
Lou
Mar 30, 2010, 03:46 PM
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leak down test
I've done leak down tests on my 4-stroke race bikes plenty o times. Easy to do when establishing TDC (top dead center with all valves closed), since I can hand crank the motor through the mag.
How does one establish TDC and hold it there on this motor?
How does one establish TDC and hold it there on this motor?
Mar 31, 2010, 07:19 AM
#27
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Update:
First of all, DO NOT BUY THE HARBOR FREIGHT LEAK DOWN TEST KIT.
It's garbage IMO. This is why...
An engine seals itself when the combustion chamber is pressurized by a moving piston and obviously the combustion process as a whole. In order to test the leakage of each cylinder properly, in the best case scenario, you'd be testing the leakage during operation which obviously is not possible.
The next best thing, is to perform the test on a hot/warm engine. With the piston at TDC (all valves closed), compressed air is shot into the cylinder via spark plug hole, and the leakage is measured between two gauges. So far so good.
Where the Harbor Freight tool fails IMO, is the air pressure that is used for the test. Yes, the gauge advertises a max pressure of 100psi, but this is BS, the gauge never operates with anything near this.
When you are prepping the device just before connecting it to your test cylinder, you have to "zero out" the gauge and crank a regulator clockwise until the needle is in the "SET" position. When you do this, if you look on the first gauge, you'll see a staggering 15psi of air is being used for the testing, NOT 100psi.
What does this mean? It means that with such a weak air pressure, you're not going to have optimum sealing in the cylinder as valves will not fully seat due to carbon deposits, rings will not square up and flatten for max sealing, etc.
Long story short, I tested with the junky tool and got readings of 10-15% leakage in my motor. It wasn't even really consistent to say in the least. I'm sending this thing back, and will re-test tonight with a MAC/Snap-On tool at 100psi... I should see much better numbers out of that device and will report back.
Lou
First of all, DO NOT BUY THE HARBOR FREIGHT LEAK DOWN TEST KIT.
It's garbage IMO. This is why...
An engine seals itself when the combustion chamber is pressurized by a moving piston and obviously the combustion process as a whole. In order to test the leakage of each cylinder properly, in the best case scenario, you'd be testing the leakage during operation which obviously is not possible.
The next best thing, is to perform the test on a hot/warm engine. With the piston at TDC (all valves closed), compressed air is shot into the cylinder via spark plug hole, and the leakage is measured between two gauges. So far so good.
Where the Harbor Freight tool fails IMO, is the air pressure that is used for the test. Yes, the gauge advertises a max pressure of 100psi, but this is BS, the gauge never operates with anything near this.
When you are prepping the device just before connecting it to your test cylinder, you have to "zero out" the gauge and crank a regulator clockwise until the needle is in the "SET" position. When you do this, if you look on the first gauge, you'll see a staggering 15psi of air is being used for the testing, NOT 100psi.
What does this mean? It means that with such a weak air pressure, you're not going to have optimum sealing in the cylinder as valves will not fully seat due to carbon deposits, rings will not square up and flatten for max sealing, etc.
Long story short, I tested with the junky tool and got readings of 10-15% leakage in my motor. It wasn't even really consistent to say in the least. I'm sending this thing back, and will re-test tonight with a MAC/Snap-On tool at 100psi... I should see much better numbers out of that device and will report back.
Lou
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