New Spark Plugs...mis-firing at 4k rpms now

[MadMadVmax]

I just took my spark plugs out of my bike and took one to the auto parts store. They replaced them with the same ones. The old ones were GNARLY...pretty black on the tip, and rusty at the top where you put the wrench. It seemed to idle a little better, but when I get up to 4,000 RPMs, the bike seems to mis fire.

Anyone know what would cause that?

 

[maleko89]

Check gap of each plug and clean the plug seat. Test plug wires too...sometimes they loosen from the boots when removed from plugs.

 

[MadMadVmax]

What should the gap be? I bought a gap tool yesterday and put some electrode grease on the end of the spark plug, and I wanted to gap the plugs, bud I don't know what they're supposed to be gapped to. Also, the boot that snaps onto the plug is the resistor, correct? Is that replaceable?? The two on the front cylinders are really gnarly looking.

 

[maleko89]

.031-.035 inches.

 

[tugla]

ngk are pre gapped but for sure you should check them that they are all equal.

they depend on the number on the plug

http://vmaxoutlaw.com/tech/ngk.htm

 

[MadMadVmax]

I went and checked the gap on all of my plugs. Here's the report:

The front, right side cylinder plug was black, the rear cylinder plug on the same side was white; both plugs on the other side were black. 2 of the spark plugs were not even gapped at .030 and the other 2 were at .035. I made every gap .035 and put electrode grease on the top of each plug and replaced the boot nice and snug.

It was perhaps the best the bike has run since I've owned it....though still not perfect. The misfire has pretty much dissappeared, and it pulled VERY hard from 5,000 to 9,000 RPM. It seemed to be a tiny bit weak from 2,000 to 5,000....

Questions?: What does the black on the spark plug mean? Why was one of the plugs white? Does it sound like I have any real problems?

 

[KJShover]

Black = rich
White = Lean
Mocha = Just right

 

[Rusty McNeil]

The resistor is inside the boot, if you take it apart you'll find a little metal "pill" about the size of a fly larvae, that's it...

The stock wires are solid core non rf reducing wires so you need that if your running solid core wires, I've found that it runs fine without them if your running "rf" wires..........

The conection at the end of the wires is a real common culprit for mis-fire,

 

[VMAX NV]

I replaced my plugs today, the old ones were all black and ashy, I could feel the difference with the new ones. I got NGK they were gapped a tiny bit tight. Put anti-seize on the threads and electode goop on the top, torqued to 13lbs. Pretty easy. Did the final drive oil too, that was even easier...

 

[Rusty McNeil]

Something interesting I've run across several times with this bike is that it'll misfire and act weird, I'll chase all sorts of problems finding nothing wrong and eventually Ohm the plugs, plugs that look "good" and clean blemish free with little to no visible wear or coloration, only to discover that one/some of the plugs will barely get an ohm reading through the resistor....Where a brand new one will ohm about 4000 ohms (I think, working from memeory on that one)

Install brand new plugs and bammo; problem gone.....:ummm:

This is with the NGK's we all seem to run.......Plugs are cheap tho, and it's the first thing I change when I'm trying to find a problem now.......

might have something to do with my Dyna ignition and Dynatek coils, I think they might be weaker than the stock setup and need perfect conditions to do thier job....having little appetite for adversity........

 

[alorio1]

Now, I'm not doughting your ability to know a miss when you hear one, but sometimes a miss fire , or what seems to be a misfire could be dirty fuel circuits........

 

[Rusty McNeil]

Now, I'm not doughting your ability to know a miss when you hear one, but sometimes a miss fire , or what seems to be a misfire could be dirty fuel circuits........

Very true! I've wasted much time troubleshooting a mis-fire when it was the carbs, and vice versa...It's kinda hard to tell sometimes; and I think I know what I'm doing most the time but prove myself wrong quite often......:confused2: