Spark Plug Removal

How do you remove the spark plug?

When I installed the FI programmer, I wanted to check the plug color first. I removed the tank, unplugged the power to the ignition module, and nothing. I could not pull the ignition module (coil, etc.) off the top of the head where it mounts to the plug. The manual just says to pull it off. I even tried (gently) pushing up with a screwdriver and it wouldn't budge. If I can't get to the spark plug, I can't see how lean/rich I'm running.

Any thoughts or tricks folks?

I simply gave it a twist while pulling up and it popped off. It's got a fairly good grasp on the plug and you will hear an actual 'pop' when it comes off.

Well, doesn't sound like there's any 'trick' to it then. I'll have to pull the tank and try it again

Yes, I was a little aprehensive about using too much force on that ignition probe too, but It HAS to come off!! So it took some doing but eventually it came off. I heard an echo in that canyon when I pulled the plug!

Thanks for the help. Finally got it out. I put a layer of inner tube on the coil so I could grip it better with the channel-lock pliers.

ZED wrote:

How do you remove the spark plug?

When I installed the FI programmer, I wanted to check the plug color first. I removed the tank, unplugged the power to the ignition module, and nothing. I could not pull the ignition module (coil, etc.) off the top of the head where it mounts to the plug. The manual just says to pull it off. I even tried (gently) pushing up with a screwdriver and it wouldn't budge. If I can't get to the spark plug, I can't see how lean/rich I'm running.

Any thoughts or tricks folks?

mine came right out...

Yeah but where's the monkey holding onto the other and of that thing?

SheWolf wrote:

Yeah but where's the monkey holding onto the other and of that thing?

lol...right here about to head out for work

i was hoping ZED noticed that it is a hamster spec wrench..lol...(just to the right of the plug in the pic)

Oh, that's funny. I hadn't noticed that.

When you decided to check your plug for color did you do a "plug chop", or anything specific while riding before you checked it?

Or did you simply decide one day to check it, and pulled the plug as it sat there?

motokid wrote:

When you decided to check your plug for color did you do a "plug chop", or anything specific while riding before you checked it?

Or did you simply decide one day to check it, and pulled the plug as it sat there?

I would think you would do a plug chop with a brand new plug. One that has been in there for a while under different riding conditions and with different mods through it's lifespan is not going to give you a good reading of how it's running now. For example, I have never checked my plug yet. I rode the bike stock for a while and then added on the exhaust and other mods along the way to over 5K miles. If I look at the plug now, it's not going to tell the true story of how it's running in it's current modded configuration. I would rather install a new plug and run it for a while and then look at it, say, after 50-100 miles of normal riding with my current mods. I'm about ready to do just that someday soon, so I will keep you posted.

That's what i was wondering. Once a plug gets dark it wont really get back to coffee/tan even if you are running in a good zone, right?

You kinda have to install a new plug to really get an idea of how your bike is running. And check it pretty quickly after install.

How you do it kind of depends exactly what you're testing for.

For example, if you're testing for a specific change like a main jet, you may want a new plug, then run it at speed under load on the highway, then cut the engine, coast to a stop, pull the plug(s) to look at them, then wait for the engine to cool so you can put them back in and be on your way. In that case, it's because you don't want your idle circuit to interfere with your reading, so you don't let it come down to idle. That's basically how I would deal with jetting the old VWs. It worked quite well.

On a multi cylinder engine you may not want to throw out a set of plugs each time you check for color. The stock plugs that came in my Unimog retail for $125 each and there's six of them. (I've converted to a cheaper version of the plug, but it doesn't perform quite as well)

In my case with the WRX it had 9k on it when I put the HP hamsters in, so I was basically interested in seeing what the bike had been doing overall sort of averaged over it's life. The color told me that it was lean throughout.

One the weekend I may get to pulling the plug again to see what a week of commuting (mostly cruising throttle) has done. I'm looking for a bit more of a brown color. If I don't see it I may enrich the curve a bit. If it's blacker, I'll likely soon get another plug and do more specific tests to see which area of the curve needs to be leaned as I don't want to lean the wrong one.

motokid wrote:

That's what i was wondering. Once a plug gets dark it wont really get back to coffee/tan even if you are running in a good zone, right?

You kinda have to install a new plug to really get an idea of how your bike is running. And check it pretty quickly after install.

My experience with "reading" spark plugs in cars and bikes over a period of 45 years as a professional technician is that the long term history of a plug is erased by current conditions. (The one exception is lead fouling which hasn't been an issue in the USA since the 1970's.)

In other words, if the plug has been running at it's design temperature for thousands of miles and has a very light brown insulator, if you were to richen the mixture by 20% or more you would have black carbon on the insulator within a few miles. If you were to then return to the previous correct mixture the carbon would burn off within 10 miles of fairly hard riding and return to the light brown color. The same applies to a lean mixture that results in a pure white insulator, as long as the plug is not damaged by overheating.

Note that you would rather err on the side of being a little rich because that makes the motor run cooler if you have changed from the stock muffler with a catalytic converter. If you have retained the stock muffler, running rich makes the catalyst run hot so you want to be as close to the perfect 14.7 to 1 air/fuel ratio.

If you google "reading a spark plug" you will find much more detailed info. Note that the sites that talk about racing apply to racing - not street use.

Hope this helps.

BluePill wrote:

motokid wrote:

That's what i was wondering. Once a plug gets dark it wont really get back to coffee/tan even if you are running in a good zone, right?

You kinda have to install a new plug to really get an idea of how your bike is running. And check it pretty quickly after install.

My experience with "reading" spark plugs in cars and bikes over a period of 45 years as a professional technician is that the long term history of a plug is erased by current conditions. (The one exception is lead fouling which hasn't been an issue in the USA since the 1970's.)

In other words, if the plug has been running at it's design temperature for thousands of miles and has a very light brown insulator, if you were to richen the mixture by 20% or more you would have black carbon on the insulator within a few miles. If you were to then return to the previous correct mixture the carbon would burn off within 10 miles of fairly hard riding and return to the light brown color. The same applies to a lean mixture that results in a pure white insulator, as long as the plug is not damaged by overheating.

Note that you would rather err on the side of being a little rich because that makes the motor run cooler if you have changed from the stock muffler with a catalytic converter. If you have retained the stock muffler, running rich makes the catalyst run hot so you want to be as close to the perfect 14.7 to 1 air/fuel ratio.

Hope this helps.

Yeah, that's great. So after a few hundred miles "normal" riding after installing an EFI unit I can get a decent read of how my engine is running? Regardless of conditions before I put on the EFI unit?

That's cool to hear.

I think I shall check it out over the weekend. Thanks.

BluePill wrote:

Hope this helps.

Good info, BluePill. +1

If you are going to be pulling & replacing your plug, would suggest you use some thread dressing to protect the head's thread & a little electro grease inside the cap will help remove the cap next time. But was really designed to keep water out of there.
Would also suggest you consider indexing your plug too.
You might think about giving that area of the plug hole a good blast of air to remove any sand or road crud, BEFORE removing the plug each time.
I do most of my reading at the tail pipe. Wipe it clean & ride a bit & there will be a tell tail color. I like what I see when it's between fig brown & coffee w/ no cream....I am getting hungry just thinking about that wr's colored pipe.