Spark plug observations

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skipro3
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Spark plug observations

Post by skipro3 »

I thought I would just pass on some info and personal experiance with my plugs here. For quite some time, my bike would start fairly easily but after warmed up and in gear, it didn't like to start unless kicked over quickly several times and with the throttle partly opened. Speculation was, the jetting may be off somewheres. I dinked with the jetting but didn't get any improvement so set it all back to where it was. Then, while cleaning up the bike this weekend, I decided to pull the plug since I haven't checked it in a while. I have an iridium NGK in there FYI. Just looking at the plug, I could tell the gap was a bit on the wide side. A feeler gauge confirmed that it was way wide. I cleaned it up a bit and regapped it. That was the problem. Now the bike starts first kick wether or not the motor is warmed up, in gear, or any other thing I can think of. I do have to turn the gas on at the tank of course, but the bike doesn't care wether I crack the throttle or not. When cold, I just turn the petcock on, open the choke, and half hardily give it a poke and she lights up. Much better now.
So, I guess the lesson here is to check the plug every once in a while even if you think it's working as it should.

On another note about plugs, there was some discussion on temperature ranges for heat. A colder plug could reduce combustion chamber temps by several degrees and a hotter plug could do the opposite. I wonder if a bike having pinging problems like CC's could be affected by the plug range in his engine? Hey CC, have you ever tried a colder plug in your bike to determine if it affected the rattle you get?
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Post by Indawoods »

Ski... I know a lot of guys who pull the plug from the box and slap it in. I have been guilty of this and usually doesn't cause a problem but I normally gap the plug.
It seems these NGK's come gapped around .32 and should be .26 to .27, for the standard BR8ES ...so it's worth checking.
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Post by KDXGarage »

I don't open the throttle when it is cold, and I open it a good bit when it is warm. If you are only cracking it a little bit when warm, do you think that may have some effect on starting, as well?
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Post by skipro3 »

Now I don't even touch the throttle after regapping the plug Jason. Before I did though, it was just a small amount of throttle open to fire up a warm bike. I tried several throttle settings in an attempt to figure out what could make the bike start easy when warm. Small throttle opening was the thing. But it was the several kicks that got me bothered. Usually I was tired if I'm starting a warm bike. Kicking over and over isn't what I need to be doing when I can't even catch my breath and slobber and drool is being spewed from my helmet. (Starting a warm bike in my case, is usually due to a crash and a crash is usually due to being over exerted and tired.) Heck, sometimes I'm so whipped I can't even sling my leg over the bike and have to find something to stand on to accomplish even that.

Inda, I don't know how the plug got "ungapped". I thought I checked it before installing it. I probably either used the wrong wire on the gap checker or I dropped or banged the plug while installing it.

I've heard and read several reports of the easy starting for the KDX under any condition, now I've got it too since gapping the plug correctly.
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Post by canyncarvr »

Ski:
Nope. Have not tried a 9 plug to see if that effects my rattle. IMO, it (pinging) isn't caused by spontaneous combustion due to excessive heat but from combustion pressures. Not to be confused with compression ratio...but an atmosphere+ in the chamber before compression even begins.

My last rides with 5% Trick114 cured the detonation and still allowed a decent enough (fast enough) burn speed for effective bottom end ops. My toluene isn't due in 'til next week. I'll check that at a few different % mixes.

I'm a believer in changing the spark plug (pick an interval that suites you) on GP. If it's 'worn' to the point it needs to be regapped, it's too round/smooth to fire as effectively as it should. Speaking of which...mine is due.

BTW...I've been waiting for a reply from NGK Tech regarding the heat removal issue. Got one canned reply..not a reply that answered my question.

In the other thread there was discussion regarding heat removal of different heat ranges of plugs. It is a semantics issue...and is misunderstood by most.

Ski gets the booby prize for bothering to think about it enough to come up with the $million$ prize (a figure of speech, folks!). The NGK writeup says a plug removes heat..that one heat range change makes a 70-100ºC difference.

That could (and does) lead one to believe that engine temp changes by that much. Nope. That can't be 'cuz there isn't any place to remove the heat to! So...a short-path 8 cold plug takes 100ºC (remember that's 212ºF!!!) more heat out of the chamber than a longer-path 7 plug? Takes it to the head/water jacket? Well...those parts are rather closely related to the cylinder, 'eh?

Sorry. That's not it. The fact that a given plug runs up to a 100ºC hotter tip doesn't necessarily have anything to do with what the combustion chamber temps are. It just gets hotter is all. The chamber doesn't run 100ºC hotter with a hotter plug. Temp may increase some..but not the amount the tip changes.

Temperature isn't a volume measurement that you can pour out of a can. The fact that a plug tip (small metal thing) changes +/-100º has nothing to do tit-for-tat with what happens to a relatively huge metal head/cylinder cooled with circulating water.

It's as Ski said. A liddle-biddy spark plug tip sticking out into the middle of the inferno of a lit combustion chamber getting hot will effect the head/cooling system some if it changes 100º...but it cannot make a much larger mass change by the same amount.

It IS a matter of BTUs, as Ski said. Now that's a 'volume' (if you will) that you can compare. IF a colder plug sinks 'X' BTU into the head..the head is going to absorb (has to) that same 'X' BTU. I guarantee that big 'ol water cooled head..bolted to a water cooled cylinder is going to be able to handle a whole lott'a BTU more than that liddle-biddy plug tip.

But....NGK don't say nuthin' 'bout that.

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Post by skipro3 »

I don't think the chamber becomes hotter or colder with a plug rate change, but maybe the temperature of the atmosphere inside the chamber is hotter or colder based on plug rating. Since you believe the ping is from combustion pressures, (defined as the atmosphere inside the combustion chamber being squeezed into a smaller volume) then realize the action of such squeezing raises the temperature to spontainiously ignite the atmosphere inside the chamber. Just compressing the gasses isn't going to ignite them; it's the heat generated when you compress gas that gets the spontanious ignition. So maybe a colder range plug would keep that atmosphere to something less than it was; maybe enough to eliminate the ping. I don't know!!!!

I've asked myself; is the combustion chamber as hot as the exhaust gasses exiting the motor? I hope not!! I ride around in a helicopter that has exhaust temps running upwards of 700 degrees C. Of course no water jacket so it's the air flow through the engine that keeps things from exploding. If I'm not moving through the air as I generate those kinds of exhaust temps, then I better be counting to ten. Because by the time I reach 10, that motor's coming apart!! (If sufficiant torque is also applied, but of course it is; the ship is airborne.)

I've got a couple of 9's in my stash I'll bring up next Friday if you want to test the theory. Then we can 'speculate over a pitcher of ice cold beer! Say, is Wibby going to get his bike together by then? Is m0rie going to make it? How about Farmerj? MMmmmm pie.......
(crap! I'm hyjacking my own thread!)
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Post by canyncarvr »

I get the heat part. I'm saying I start with x+ (x=combustion chamber charge before porting) with the port job. Compressing more air results in more pressure. That is the whole idea of porting something..to improve airflow. If, after you're done porting something, every air measurement (amount of it..how it moves from one place to the other, how well it suspends 'atomized' fuel etc) remains the same as it was before it was ported, you just accomplished nothing.

If 'maybe the temperature of the atmosphere inside the chamber is hotter or colder based on plug rating' then 'I don't think the chamber becomes hotter or colder with a plug rate change' doesn't follow.

If the chamber temp goes up, the chamber temp goes up. Wow. I amaze myself sometimes with my brilliance!!

A 9 won't run hot enough to clean-up after itself. I'm still messing with my FRP-ported goofed up jetting. Consider I have detonation problems (too lean? Or just insufficient octane?) AND goo coming out the tailpipe..then making it more lean isn't the answer.

Besides...the warmer it gets (same day, same fuel, same type of riding) the less spoo I get! So..the richer it runs (temp increase) the less it spits? But..that can't happen!

But...it does. BTW..I am NOT jetting by spooge. I'm jetting for the best running bike I can get...and noting what happens to spoo in the process. If my bike is running well enough to make me happy...I don't give a rip what the pipe looks like. Other riders make fun of my spitting bike...tell me I don't know what I'm doing and all that. Spoo on them!! I'm familiar with the process. I know what works where and why. Well....he said hopefully! :wink:

Maybe Wibby will show up on his V-Strom!! I haven't gotten a confirmation from m0rie or famerj.

Well guys?

Yeah...'crap' is right!! But I'm with 'ya!!! :wink:

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Post by skipro3 »

What do you mean the 9 won't run hot enough to clean itself? You said you haven't tried it yet. You don't jet by goo, so don't assume the plug will foul just yet. Try it and KNOW the plug will foul. (I learned that from someone who once told me you can't know what works best without finding out what doesn't work best first. Who could've told me that!)

Now I've got a headache!!! I don't know physics.

P.S. My bike smokes 10 times MORE when I get it hot than during normal riding. For example: I get ripping up a fire road, under a good load, and when I get to a stop, my bike looks like it has a pile of wet straw ignited in it's tailpipe. It is a lot of smoke. The motor is warmer, say 20 degrees or so, than when riding normal single track loads and speeds. Almost zero spooge though. After a days ride, a tissue could be used to wipe the inside of the pipe clean. Well, that might change, I'm switching to MX2T or it's equivialent to see if the smoke can be reduced.
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Post by canyncarvr »

I 'know' a 9 will be too cold because I've run a 7.

So there!

Put that in your thinking cap!!

I don't know who told you that...but he's (it/she/they/them) probably a maroon. ;)

Maxima SuperM is 'smokeless'.

ha ...Ha ...HA HA HA HA ....!! that's funny.

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Post by skipro3 »

I may be red faced but maroon?

Yup, Maxima SuperM is what I run. Smokless until I get on the pipe and work the upper rpms for a bit, then watchout and don't be following too close! Ha!
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Post by JD »

I can't resist throwing in my .02...

A hot plug could ignite the fuel air charge with enough compression. It would be acting like a glow plug in a diesel engine.

I have run the BR9 plugs and fouled every one of them. Mine is an unmodded motor though.
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Post by Indawoods »

In the 92 I had, I ran 9's... no problems at all. Never fouled a plug. Still switched to 8's and the plug cleaned up nicely. Only run 8's now.... would never run a 7... just too hot I think. :?
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Post by canyncarvr »

Yes, a 'too hot' plug can cause preignition...but it would be running way past the range of what's acceptable as a plug temp. Terms as 'too hot' or 'too cold' in regard to heat ranges of plugs isn't referring to a preignition point.

BTW...I just changed my BR8EG. How's .045" sound!! Yep. That's what it was!!

heh heh...a bit 'fat' 'ya think?

How much too big was yours, Ski?

Put the new one in @ .030"
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..whoever 'he' is.....

Good thing I have an Electrex lighting coil in the bike for improved exciter atcion!!!

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Post by skipro3 »

Probably not that big. I regapped to .028 though. Since mine was an iridium plug, I don't think it wore to the larger size, just sloppy workmanship on my part is my guess. How about you? To what do you attribute the .045 gap in your finewire plug?
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Post by canyncarvr »

Wear. It was .030" when installed. I regapped it at the time.

When was that?

About a year ago, I think.

Comparing the two (new/old) it's easy to see that it's not merely a matter of gap. The used plug has a shorter center electrode and the groundstrap is roundy.

I should have changed it before now. The last instance of using a plug for too long resulted in a piston with a hole in it.

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Post by KDXGarage »

The last instance of using a plug for too long resulted in a piston with a hole in it.
So you let this one go for a year? :grin: Change that plug.
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Post by skipro3 »

I agree with Jason. Dude, learn the lesson! Change that plug like it's your underwear! At least every other month or so. (No wonder my kids want to put me in the home they saw on 60 Minutes!)
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Post by IdahoCharley »

Boy you guys must ride alot. I change mine every year when I rebuild and yet to see any significant increase in gap. Maybe a .001 inch but that is it!! No fancy plugs used by me - maybe that is why mine last a long time.

P.S. Normally average 1100-1300 miles/year.
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Post by canyncarvr »

Yeah...I did let it go for a year...but I wasn't in the sand riding WOT 99% of the time, neither.

Still...I should've changed it out six months ago. I'll put it on my underwear schedule!! :wink: I promise!!

IC...try an EG. I'll bet you will notice a difference.

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Post by 89kdx200rdr »

try an es. also just for shits and giggles try this. nothing to do with the plug tho. before you start your bike put it in gear and rock it back and forth you should hear/feel the piston moving. after this start as usual let me know what it does for ya. helps me start on first kick.
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