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0 compression?!

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sham:
Hey guys, rather confused so there are a couple questions here I think...

Background is a Kawasaki Z250, bought non starting and still non starting. I have rebuilt the carb (CV32, but have not removed/changed the float valve seat - not sure how, that's another question) and then realised I really should check the compression of the engine...the tester set arrived today and I tried to test for compression by removing the spark plug, opening the throttle and hitting the starter button.

Usually, I do get sparks from the spark plug, but for the compression test, I got a 0 reading. Nothing moved at all.

So first question relating to this thread is, are there any reasons why this might be? I checked the starter relay and it is good. I didn't have time to check the starter motor, but I'm under the impression that seeing as I am usually getting sparks from the spark plug, this is not the issue. Am I correct?

Secondly, this is the second time that I have been getting sparks from key hole, which heats up my key and produces a burnt smell. Dumb question, but is there a problem with my electronics? I have not noticed this before. With this key hole sparking issue, I have also noticed that my signals are not working anymore. My battery is reading at 12.52V when plugged into the bike, and I have been trying to give it a bit of a charger every month or so.

I guess thirdly, I am wondering what else should I be looking into to get the bike started? The reason I rebuilt the carb was that I wasn't getting any fuel through them when I tried starting the bike. Now that I have rebuilt and rejetted for pods (have not put in a new diaphragm or been able to remove the float valve seat as mentioned above), I am thinking that may be due to either of those reasons.

Any advice would be greatly appreciated.

Thanks.

TommyRocker:
Yes, there is a problem if your lock cylinder is sparking at you.

As for the compression question:

Spark, Fuel, and Compression are unrelated, but all required for a gas engine to run.  When you press the starter button, does the engine turn? If it does not spin, you will not build compression.  If it does spin, but you still are not building compression, then there is another problem.  You are obviously new to engines(just an observation, not a slam) so start by making sure you are using the tool properly.  Is it screwed into the plug bung properly and sealing well?  Is the pressure release valve held open?

Next, have you checked your valves for proper gaps?  If the valves are not closing, you will not build compression.  If the valve lash is correct and the cams are timed properly, move to the next likely problem. If it was a leaky head gasket or VERY worn rings, I would still expect to see some compression, though it would be low.  If the engine is spinning, the tool is sealing properly, and the cams and valves are all set right, but you are still seeing 0 compression, it may be time to pull the head.  You may have bent valves, a hole in the piston, et cetera.  I'm unfamiliar with this bike, but I am assuming it is a 4-stroke.  If not, oops...

As for spark:  if the engine is not spinning, you probably won't be seeing spark...  But start with the compression part first.

MILKY:
i know there a lot of really helpful people on this forum.. maybe i can help you help yourself with someone elses help :)

check this guys page

http://dansmc.com/troubleshooting2.htm



Ok, it turns over, but does it have any compression ? Take out the spark plug(s) and ground the plug wire leads to the engine. This is to prevent burning out parts of the ignition system. Screw in a compression tester gauge. Open the throttles wide open and crank the engine. If you don't have the throttles wide open, you will get a low reading. You are going to need at least 100 PSI (pounds per square inch). Depending on the compression ratio, you could have 150 to 170 PSI or even higher. I have seen engines run on as little as 65 PSI (an outboard) and I have had them NOT run on as high as 90 PSI (a chain saw with a pinched ring.) A down and dirty way of testing is to put your thumb over the spark plug hole and turn the engine over. No matter how hard you push your thumb down, the compression pressure should blow your thumb off. If you can hold the pressure with your thumb, there's not enough compression to start the engine.

If you have a four stroke engine, it's always worth while to check the valve clearance to see if one of the valves is tight and leaking compression. See the Valve Clearance Page. To figure out whether it's the rings or the valves try this. Lock the crank with a wrench, with the piston at TDC (Top-Dead-Center) and run some compressed air in through the spark plug hole. Make sure you have a good hold on the crankshaft wrench or the engine will spin, throwing the wrench off ! Now listen. If you hear air coming out at the carb or air cleaner, the intake valve is leaking. If at the exhaust pipe, it's the exhaust valve. If at the engine breather, it's the rings.

While the spark plugs are out, and we are cranking the engine over a lot, do it just a bit more. Do it till the engine oil light (if it has one) goes out, or until you feel that enough oil has been pumped to all parts of the engine. If you use the kick starter, kick it maybe, 30 times or so. If you use the electric starter, crank the starter no more than 10 to 15 seconds. Then let it sit and cool off for a minute. Motorcycle electric starters are very fragile and very expensive. If you crank away for a minute or two, the starter could be burned out.

So we find we have compression, what next ? Check for spark. I like to use a new spark plug with the ground electrode bent straight out and a clip soldered in the side. Connect your tester to the big thick spark plug lead and crank the engine. You should see a nice big fat blue spark. If you don't, disconnect the engine kill button. If there still is no spark, you will need to determine if the engine has points or electronic ignition. Most (but not all !) bikes built before 1980 have points ignition. Most bikes built after 1980 (but not all !) have some sort of electronic ignition system. If in doubt, pull one of the crank end covers (Usually 2-3 screws) and look ! If you have a battery and coil points system see the points page If you have a points magneto system see the Magneto page. If you have an electronic ignition system see the electronic ignition page.

MILKY:
also

sorry to be a copypasta but this might help you and others

You can have the hottest cam, perfect ignition timing, clean carburetor, and fresh gas, but without good compression... that engine is not going to run. The first thing I do, when a non running bike comes in, is to run a compression test. If the engine does not have at least 100 PSI (Pounds per Square Inch) in each cylinder, I won't work on it, except to rebuild it. It would be a waste of the customers money if I "Tried" to make it run.

100 PSI is the minimum. It should be 125 to 150, and some engines have as high as 170 PSI or more. Yes, an engine can run with lower compression, but it will run very poorly. I've seen old, big, multi-cylinder outboards run with as little as 65 PSI and some lawnmowers run even less. However, for motorcycle engines 100 PSI is really on deaths doorway. Use your time to rebuild the engine, not to get another five or ten hours of life (maybe !) out of it.

The drill is simple. Remove all the spark plugs, ground all the spark plug wires or turn off the ignition, if possible. Screw or push the end of the gauge into the spark plug hole, open the throttle wide, and kick away. I like to kick (or turn the engine over with the electric starter) about four to five times and then check the gauge. Remember the reading, release the pressure on the gauge, by pushing the little releases, and do it again. If the reading changes, do it till you get several readings that are all the same. That would be the correct pressure.

When you remove the spark plug, it might be a good idea to loosen the plug a bit and then blow out and around the plug with compressed air. This is to blow out any bits of dirt that might fall into the engine through the spark plug hole, as you remove the plug. This is an especially good idea on dirt bike engines with deep, forward facing, spark plug holes.

Technically, You should do this when the engine is hot, but I don't like burning my fingers, so I always do it when the engine is cold. A hot engine would probably read a few pounds more, but a cold reading will tell you what you need to know. Run the test on each cylinder. All the cylinders on an engine should be within ten pounds of each other. In other words, a four cylinder engine reading 145 PSI, 150 PSI, 147 PSI, and 155 PSI would be considered good. If it had 135 PSI, 150 PSI, 150 PSI and 155 PSI, it would not be considered good. Something is starting to go wrong with that first cylinder. OK, you have a cylinder that reads low. Is it valves or rings, leaking that compression ? A quick, down and dirty test is this. Squirt some oil, maybe a teaspoon's worth, into the cylinder through the spark plug hole. Now run the test again. The oil will hold compression for several turns of the engine. If your retest with oil gives higher compression, you will know the rings are worn. If there is no change in compression, it's the valves that are leaking. If you think it's the valves, it's always a good idea to check the valve tappet clearance. If the valves are tight, they could be leaking compression. If the valves are tight, reset them to the proper clearance and test again. if your compression comes back don't thank your luck, thank Jesus ! He just saved you an engine rebuild.

This test is one of the most important tests you can make. Time and time again, I see people work for hours trying to get an engine to run or to run good. I ask "Did you run a compression test ?" they say "Oh, it has compression" I ask again, "Did you do an actual test ? What was the PSI ?" They say "It feels like it does !" So they run a test, and guess what ? No, or little, compression. Don't waste you time on a dead engine. Run a compression test first thing.

If you have an engine with Constant Velocity carbs the test is still done the same, with the throttles wide open. You might think they would read different, but they don't seem to.

Sometimes the spark plug holes are kind of weird in the size department and you will have to use an adapter on the end of the compression tester gauge. You can get a lot of different types of adapters, but sometimes you may need a special adapter that no one sells. You can try to use the push type of tester. It has a rubber tip that fits into the spark plug hole and is held there by hand pressure. Sometimes, due to the position of the spark plug, that will not work. If you can't buy the right adapter you can make one out of an old spark plug.

To make one, simply take a spark plug that fits the engine you want to test and remove the part of the metal base that is crimped over the ceramic portion of the spark plug. You can do this with a hack saw, and the crimped part will come loose like a ring. Now you can knock the ceramic part of the plug out with a drift from the nose end of the plug. This leaves you with just the metal portion of the plug. Now you can cut threads inside the end with a tap, like the one above, or weld it up with metal and redrill it to the right hole size if the plug is too big to tap as is.

If you don't have a compression gauge handy, all is not lost. A down and dirty way to do it is to simply press your thumb over the spark plug hole and hold it there tight. Now have someone kick the engine over. No matter how hard you push your thumb, the compression pressure should blow it off the hole smartly. If it won't, you don't have enough compression to start the engine.

Really?:
I had 0 compression on the YZ50 I picked up.  Figured my gauge went bad as it was one I have had for hmmm about 30 years now.  As I was messing with the carb, I noticed the head/jug move.  Snugged the head bolts, still no compression.  Figured it would take less than 10 minutes to have it down to the case so I tore it apart.  No gaskets or rings.  Found the problem!

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