cylinder not firing

"The plug wires from the coil to #1 and #4 plug are usually long enough to allow swapping them for each other. But if the wires aren't long enough, let us know. "

4 wire is just a bit short seeing as its right under the coil. advice? Should I remove wires from right side coil and swap them to get the desired length?

squints wrote:

"The plug wires from the coil to #1 and #4 plug are usually long enough to allow swapping them for each other. But if the wires aren't long enough, let us know. "

4 wire is just a bit short seeing as its right under the coil. advice? Should I remove wires from right side coil and swap them to get the desired length?

To clarify -- one coil is supposed to fire outside plugs #1 and #4 (believe it's the left-hand coil closest to the shift lever). And the other coil is supposed to fire inside plugs #2 and #3 (believe it's the right-hand coil closest to the rear brake lever). Am also thinking the original coils had their plug wires permanently attached (wires non-removeable from the coil). Usually the plug wires from the left-hand coil are longer than the plug wires on the right-hand coil. This is because the left-hand coil plug wires have further to reach going to the outside plugs #1 and #4. And the right-hand coil plug wires have a shorter reach to the inside plugs #2 and #3.

In any event, the coil firing the outside plugs #1 and #4 will require longer plug wires to reach the longer distance between the outside plugs (as the distance between the inside plugs is shorter).

If your plug wires are removeable from the coils, I suspect that they are not the original stock coils.

First, put a brand-new sparkplug in #4 cylinder.

Am guessing a little here, but I believe on your bike that the left-hand coil fires the outside plugs #1 and #4. These are the two longer plug wires. And these are the two plug wires to remove from the outside plugs #1 and #4. Now attach the previous #1 plug wire to the brand-new #4 plug, and attach the previous #4 plug wire to the #1 plug. Don't involve the other two plug wires from the other coil, because inside plugs #2 and #3 are not part of this test. If both coils have removeable plug wires, it would be okay to exchange some plug wires between the coils if that would allow the wire lengths necessary to reach the plugs.

Next, crank and test run to determine whether #4 is still not firing (still cold exhaust header pipe) OR whether the non-firing cylinder moves to #1.

The non-fire will either continue on #4 or move to #1. Easiest to use a hand spray water bottle for the water spray test onto the exhaust headers with engine running.

The results of this test will provide some diagnostic clues regarding the ignition. And help us better decide on what to do next with regard to assuring existence of a healthy spark especially in #4 cylinder.

Wanting to assure the ignition components are okay before next considering compression and valve clearance (and we should defer addressing carbs until last).

If the #4 plug wire into the coil is removeable from the coil, maybe it's not making a good solid connection at the coil where it screws into the coil. Maybe the plug wire is faulty. Maybe the plug cap is faulty. Any of these things. The test results will help point the way.

Good Luck!

First i got to say thanks, you kick ass. I'm a doofus and I really appreciate the walk thru.

ok,now from your descriptions it seems I have been confusing you. I was telling you the wrong # cylinder. I believe it is the #3 (not 4) that is not firing. Counting L to R while sitting on the bike its the 3rd thats not firing.

So I will use your info and swap the wires as told before from the 2/3 coil. I will also test the connections to the coils, they are removable -it looks stock, anyhow thats how they came:dry:

i'm off....

swapped lead wires from R side coil (2/3 plugs)and there was no life still on cylinder 3. Next step compression?

squints wrote:

swapped lead wires from R side coil (2/3 plugs)and there was no life still on cylinder 3. Next step compression?

Yes. Compression is next test. Remember to hold throttle wide open during the test. Please post the psi figures and we'll go from there.

I just had a simular freak issue with my bike the last 2 days......

Bike sat for a week while I was getting over a cold and the bad weather here. I started the bike yesterday to take her out for a spin and it was missing and just wouldnt idle up to normal and I noticed a "miss" coming from the #1 carb. Got the bike back home and it wouldnt smooth out and run right for nothing. Im figuring the carbs are dirty since me and carbs never get along. Today after work I started the bike, it ran like crap, so I felt the #1 pipe after running the bike for 2 minutes. Pipe was ice cold ! Pulled the plug, checked for spark, had a kinda weak spark so I swapped the plug with the #4 plug, started the bike and all cylinders are firing and bike is running fine ! Who knows, the plugs are fairly new with less than 200 miles on them ??? Freak thing I guess but when I pulled the plug and checked for spark it looked a little weak. Not sure if it was the plug or what. It must have been cause the spark looked really weak but when I used a "spark checker" it had a very strong spark. If your checking for spark by laying the plug on the motor and cranking and looking for a spark it could be misleading.

The plug shown in the picture above is not firing. Even if compression was very low a firing plug will not smell like gas and be black like that one.

squints wrote:

swapped lead wires from R side coil (2/3 plugs)and there was no life still on cylinder 3. Next step compression?

swapped lead wires from R side coil (2/3 plugs) and there was no life still on cylinder 3 --- Just to confirm, this was with a brand-new NGKB8ES sparkplug in cylinder #3 ?? Because a questionable sparkplug will invalidate the test. Wanting to assure #3 plug is producing a healthy fat blue spark under compression, and rule out to the extent possible any suspicion of a faulty sparkplug.

Bottom line here is trying to rule out an ignition proble as the reason why there is no combustion in #3 cylinder. If the #3 sparkplug is producing ample spark at the correct time, then the non-combustion issue in #3 cylinder is most likely caused by either a compression fault or a carb fault. When convinced of having ample spark at the correct time in cylinder #3, we next determine whether there's any compression problem in #3 cylinder (before resorting to the carbs). This is because even perfect carbs cannot compensate for faults in ignition, compression, or fuel delivery. So all these other things should be checked first, before the carbs.

Good Luck!

Try taking the plug wire off and then put it back on but leave a small air gap. The spark will jump the gap but it will be a hotter spark. I have to do this every once in a while on some of the bikes I work on. After the bike warms up you can put the wire all the way on. Worth a shot at least.

ok, i've read up on testing compression in the manual, it reads. "turn the kill switch off, hold throttle open, and crank the engine..." how do i crank engine without bike starting? Am i supposed to remove all 4 plugs when i check compression?? little help....

squints wrote:

ok, i've read up on testing compression in the manual, it reads. "turn the kill switch off, hold throttle open, and crank the engine..." how do i crank engine without bike starting? Am i supposed to remove all 4 plugs when i check compression?? little help....

One way to do it is to pull the plug caps... Shut off the fuel...


BTW: Patton you have the patience of a saint

squints wrote:

ok, i've read up on testing compression in the manual, it reads. "turn the kill switch off, hold throttle open, and crank the engine..." how do i crank engine without bike starting? Am i supposed to remove all 4 plugs when i check compression?? little help....

Am i supposed to remove all 4 plugs when i check compression?? -- Yes, that's the best way, because the motor spins over more freely using the electric starter, and all the plugs must be removed from the cylinder head anyhow to test all the individual cylinders. Incidentally, when later reinstalling the plugs, would recommend using 4 brand-new NGKB8ES sparkplugs.

turn the kill switch off -- some bike models won't even spin over using the electric starter unless the engine kill switch is in the RUN position.

how do i crank engine without bike starting? -- it of course won't start with all the plugs removed.

Remember to hold the throttle in wide open position while spinning the engine over with the electric starter in doing the compression test on each cylinder.

Let us know the compression psi number on each cylinder resulting from the tests.

Good Luck!

BTW: Patton you have the patience of a saint [/quote]

this is true.. :laugh:

we all got to start somewhere