Compression, spark, heat...what's missing?

SO...Does anybody know what it means when you can remove a plug wire while a bike is running andd NOT have it shut off?
Some would say no spark....but there IS fire coming from my cylinder, because the exhaust pipe out of the motorhead is hot.
Some say no compression...but when the plug is removed and I place my thumb over the hole and try to start the bike it sucks on my thumb...so there's compression.
I thought, by some STRANGE twist of fate, that maybe only HALF of my coil was working, so I switched spark wires between one and four....same thing....so I know the coil is working properly...it also gave me a good shock when I let my mind wander for a second. Haha.
Am I missing something?

Your bike should have no problems running on 3 or even 2 cylinders. I can barely hear a difference when I run on 3 cylinders.

ok, thanks...that's all well and good, but still SOMEthing is going wrong and I would like to understand what it is and how it went wrong so as to hopefully be able to avoid and fix the problem.

I'm no expert on anything (yet) but you might want to check the fuel. It could be bad or have a wrong air to fuel ratio. I might try moving up an octane level and see how that works. It could be firing to early causing a "knock" or uncontrolable fire. Honestly, I have no idea, but thats my two cents...

Bicycle Lee wrote:

... anybody know what it means when you can remove a plug wire while a bike is running andd NOT have it shut off? Some would say no spark....but there IS fire coming from my cylinder, because the exhaust pipe out of the motorhead is hot....

If plug cap is completely removed from the plug and placed far enough away from the plug to avoid arcing to the plug, the plug will not fire. Believe exhaust header from the non-firing cylinder is being warmed by heat radiating from the adjacent header(s) and warmth transferred from the head.

Easy to test with a common water spray bottle, especially just after cranking up a cold engine. The water spray will soon sizzle on the exhaust headers from normally operating cylinders. The water will collect and run off header from the non-combusting cylinder, even though it seems warm. Best to NEVER feel the header with hand or finger on a warm or running engine. SPRAY them instead.

Go ahead and give it the sizzle test.

Pat1707 wrote:

I'm no expert on anything (yet) but you might want to check the fuel. It could be bad or have a wrong air to fuel ratio. I might try moving up an octane level and see how that works. It could be firing to early causing a "knock" or uncontrolable fire. Honestly, I have no idea, but thats my two cents...

My fuel is fine...I KNOW that. The timing might be off and I need to look into that. and I know that the cylinder won't fire if the plug cap is removed...but removing it while the bike is running should kill the engine....THAT'S my point.

Bicycle Lee wrote:

My fuel is fine...I KNOW that. The timing might be off and I need to look into that. and I know that the cylinder won't fire if the plug cap is removed...but removing it while the bike is running should kill the engine....THAT'S my point.

Just to clarify....Removing the plug cap with the bike running will NOT kill the engine. There's 3 other cyls. there cranking away. Removing 2 might, 3 will, but not just 1.

correction: if I remove ONE of the other plugs it kills the engine.

the thumb test is not always acurate enough, you could have low enough compression that it feels ok, you need a minimum of 70 psi for combustion, try and get a hold of comp. tester and verify, after that you can move on to other things

i have a 750 doin the same thing. i can pull no 2 and no3 and there is no difference in the exhaust sound. headers are also hot. you probably have spark but its weak. pull your point cover off and make sure that your contacts are clean. you may need to have your ignition timing checked, and you also just may have a weak coil. after i check mine out i will let you know what i find. i had the same problem on the previous motor so i'm gonna say it might be common. i switched coils completely and got the same problem on 1 and 4.

so if you switched coils on the previous engine and it didn't help, it could be timing and/or maladjusted points?
I'm just trying to get to the bottom of this...I'm still getting pretty bad gas mileage too...about 30 miles to the gallon...ugh.
My brother offered to give me his Virago...maybe I'll take him up on it :laugh:

My bike will run just fine one Cylinders 1 and 2 with 3 and 4 unplugged. It will not however run on 3 and 4 with 1 and 2 unplugged (shrug).