So I just did a leak down test, and I had 100% loss on both cylinders. I followed the directions (first time I've done it), and I'm a little confused. Both cylinders had compression, although they were both below the spec range. Is it possible to have 100% loss in the leak down test and still have compression?
i think so, if you didn't put the piston you are checking leak down on to TDC and a valve/s was party open.
Right, make sure the cylinder you are testing has all of the vales closed, you can check this with the timing marks and by making sure the cam lobes are away from the valves, like when you adjust them.
I went by the timing marks on the rotor. I checked the valves a few days ago, and everything was in spec. I tried the leak down test on another, blown motor I had lying around. Pretty sure it dropped one of the valves (haven't taken it apart yet); BUT, it's the same issue, 100% leak in both cylinders and that's what has me wondering if I'm actually doing the test correctly. So my original question stands: is it possible to have some compression (~100psi) in a cylinder and yet have 100% leak? If not, then at least I know I'm doing the test wrong and can try again. Btw, I'm using the MotionPro leak down tool. I read the directions and even watched a video of a guy using it. I'm 90% sure I'm using it correctly.
Is the piston at TDC? Are the valves closed? Where is the leak coming from? If you have 100 psi of compression it doesn't matter. Take that hunk a junk apart and replace errythang.
i don't know how this would affect the leak down test, but you gotta have the shrader valve out of the hose to do the leak down. i'm not a builder, but have had mulitple leak down tests done, and done lots of my own comp tests. i can't see anyway possible you could have good compression, with 100% leak down.
Make sure that the cylinder you are checking has all 4 valves with the lobes away from the buckets, you might be 180 out for that cylinder and 2 of the valves might be slightly open.
and I presume you have the service manual for your bike which will tell you which cylinder is at tdc when the timing marks line up. or you can pull the head cover(s) off and watch the lobes just to be sure. 100 psi is low but to have complete leakdown seems incongruous.
Trying to read between the lines here but it sounds like you are putting the bike at TDC for cyl #1 (using the timing marks) and then checking all 4 cylinders. That's only going to work for cyl #1/4. You have to put each piston at TDC before checking that one. Easiest way to do so is to drop a long screwdriver down the spark plug hole, rotate crank until that piston is at the very top of it's stroke, then do leakdown on that cyl, repeat for each cylinder.
It has to be TDC compression stroke, if you are at TDC exhaust stroke, valves are opening and closing. If you properly check #1 then #4 has to go up and down again.
you guys are presuming a lot about firing orders...and ignoring the fact that the op stated that the problem was on "both" cylinders, which suggests to my pea brain that he has a twin.
Pretty sure his bike is a Ninja 250 cause that is what his racer profile says. Again where did it leak from? Intake, Exhaust, through the oil fill cap?
Leave the leakdown tester connected and just rotate the crank through a complete cycle. If during the crank rotation you start to feel resistance (from the testers air pressure) you'll know that that you're coming up on the correct crank mark for that cylinder. Disconnect the tester, line up that upcoming mark, and test.
Well, I didnt get a chance to do it again, but I did get a chance to turn the crank with the valve cover off, and I began to wonder about what you wrote here. That's when I realized that I may have taken the first reading during the exhaust stroke.
And yes, it is a Ninja 250. Thanks for the help guys. Might get a chance to do this this afternoon, and I'll report back.
Ok, I was 180 degrees off. Cylinder #1, less than 10% loss, but that's not at the 1T mark on the rotor. In fact I never measured it at 1T because the rotor would just spin right over it. I eventually did what Steve suggested, and that's when I got the reading, which was at a 1F mark, just before the 1T mark. What is 1F? (Btw, the cams definitely look more TDC at the 1F mark than the 1T mark, which I was able to get to on the exhaust stroke.) Cylinder#2, which had the lower compression was leaking 26-7%, mostly from the exhaust and I think a little from the crankcase breather tube (could barely feel something). Kevin, do the new gen motors have the 1F mark? Also, why would the motor let me hand crank to 1T on the exhaust stroke but not on the compression stroke?
