Dead cylinder!

Hey guys,it's me, I have suspected that my #3 cyl. was dead due to the lack of bluing on the pipe. I used the water on the pipes test to confirm it. I checked the spark, it was good. I checked the carb and there didn't seem to be any obstruction in the jets and it was getting fuel. I then did a compression test,( I think I did it right, I hooked up the guage and turned over the engine a few times and the pressure seemed to "build up". Is this right:unsure: or should I read it after only one compression stroke?)and the compression is comparable to the other cyls.110 was the most#4, and 70 the least #3. I only had about 75 on #2. I then cranked it without the filters and noticed that a mist was coming back through the carbs. What's the deal? Hope I don't have a big problem:dry:
ThanksB)

Bluing is due to too lean a mixture and/or timing issues. If I remember correctly, one of your latest postings was in regards to timing, valve shims and valve adjustments.

So assuming you have completed the above correctly, is it possible that the bluing is not as noticeable?

Is the bluing on your exhaust header from when you got this bike or after the work completed on a shiny header, this is the only cylinder exhaust that is bluing?

If all checks out, I'd go with #3 carb not tuned correctly, too lean or different jet or etc...

Possible something else but I'd check that for sure.

OMR

How did you do the compression check, WOT, the numbers seems low for compression.
also have you checked the valves

You mentioned there was a mist of fuel coming out the card on the cylinder in concern.Have you checked the valve clearance with the engine hot or operating temp??It sounds to me that the intake valve is a touch to tight holding the valve open which will give you low compression reading and fuel spray out of the air cleaner side of the carb.Good luck

Compression test is done Wide Open Throttle, with no plugs installed. Nice hot engine...

Crank until the guage stops rising, theres your compression. Should only take bout 3-4 turn overs to max.

The gauge should stay exactly where it stops. If it starts to fall, you have a pressure leak. Add couple teaspoons oil to the cylinder and do it again. If the pressure rises signifcantly, then rings are pretty bad. If no change, then most likely valve not seating/closing properly.

Properly done "leak down" test after that can reveal specifics...

Cheers.

Hey guys!
Well I have done the valve adjustment. I warmed up the engine and checked the compression like I was instructed. My #'s are as follows;
#1-80
#2-70
#3-70
#4-80
I know these #'s are low but the good news is they are consistent! However that doesn't answer my question about the dead cylinder. I was rechecking the timing and when I put the signal picker'-upper' on the #3 plug wire I had to shake it to get a signal. Now, I know that those sgnal readers are touchy and this may belong in another thread but, is it possible for one coil to be half bad?
Thanks for all your help!!
BTW, Is it really bad to have too much valve clearance?

thadley55 wrote:

Hey guys!
Well I have done the valve adjustment. I warmed up the engine and checked the compression like I was instructed. My #'s are as follows;
#1-80
#2-70
#3-70
#4-80
I know these #'s are low but the good news is they are consistent!

If those are correct, the engine is hosed.

thadley55 wrote:

BTW, Is it really bad to have too much valve clearance?

The valves will get "clicky" if the clearance is a bit too wide (like a few thousandths) but won't affect performance much.

Perhaps you should start by mentioning which bike is being discussed. Next, you did a recent valve clearance check? What were the clearances for exhaust and intake valves? There is a possibility that you set the clearances incorrectly and the valves are hanging open a tad. I wouldn't get on the non-firing cylinder until I sorted this out. If the valve clearances are within spec, do a compression test AGAIN with the throttle held wide open. Having the engine warm will not make a huge difference. Do the compression test again but this time do it a tad differently. Put one teaspoon of motor oil down plug hole #1. Test for compression. Record reading. Do the same for the other three cylinders in turn.

If the compression readings shoot up, this will indicate the rings are not sealing as they should. If compression doesn't shoot up a bunch, this indicates the valves are the issue. This points back to valve clearance issues.

With compression like you have noted ~70 to 80 psi, the bike will likely start but performance will be poor.

You will then move to ignition issues. First thing to do is to swap the #3 plug wire with the #2 and see if the problem stays on the third cylinder. If it moves, you have either a wire, cap or spark plug problem on #2. Quit messing with the gizmo you are using... try this method. if the problem stays on the #3 cylinder, then the carburetor is the probable issue.

When the bike starts, it may not fire at idle but if you take it on the road for a bit, stop and spray the pipes with a squirt bottle filled with water. Water will vaporize if the cylinder is firing but pop and spit off the pipe if it isn't. Pinpointing whether the cylinder is firing at higher speeds is important to get you to the part of the carburetor you need to focus on if you need to either clean or disassemble.

I strongly suggest you approach the problem and go through the steps as I suggest. If you don't you are essentially jumping around and chasing rabbit trails and really not proving anything conclusively.

Thanks for your replies. That "gizmo" I was using was a timing lite, I guess I should have said that, sorry:blush: . I have addresed the valve clearance issue and my clearances are good. I havent done the oil in the cylinder test for compression yet but I will soon. I'm pretty sure that spark is not the issue because I have checked the plug for spark and switched the wires as I read in another thread. I ran the bike around a bit and then sprayed the exhaust, it was hot. I then pulled off the pod filter and put my hand over the intake and barely felt any vaccum. I have come to this conclusion(which one of you have said already)my engine is hosed:( . This can only mean one thing.....complete rebuild!!:ohmy: Now comes the challenge of telling my wife that the 2 wheeler I bought to save money on gas is going to end up costing more than we paid for both vehicles we currently own:ohmy: .(I got good deals:laugh: )One more thing, this is my KZ900
ThanksB)

complete rebuild

....:blink:

Sure but you might possibly only need a $200 valve job....
Probably best to follow everything that has been posted back at you before totally re-building your motor.

As written, if your timing is off (CAM lobes), valves will not seal properly thus you will measure low compression.

Same time, you have the time and funds... build away!

OMR

what kind of clearances did you get on the valves when you checked them?

I don't remember which valve had how much clearance but I had no less than .002" and no more than.006".