Spark plug Science experimentation Hawk 250

[Ghenghis]

Bought a Hawk 250 a couple months ago, red with black rims, reading posts from here and watching MotoCheeze's videos won me over.

I had a late 70's Yamaha 125 Enduro a long time ago, got it used when I was 13, learned how to replace and adjust the points/condenser I ordered out of the JC Whitney catalog as it would hardly run when I got it. Crazy to think that we had to actually ask someone, usually a friend's mechanic dad, or an uncle, how to fix things. I rode the wheels off that bike, the wheels never actually came off but the muffler began to form rust holes on the outer skin. Had to leave it behind when we moved from the country into the city, it had broken down so I didn't get much say in the matter. I've always wanted to get another Enduro, the ability to do some light off-roading and legal street driving always seemed like a win win.

Finally, nearly 30 years later I decided to get another Enduro. I've always had an interest in anything mechanical, I had to know how it worked, and what I could do to make it better. I'm an information sponge, so I know at least a little bit about everything. My Hawk doesn't have 20 miles on it yet and I've had the carburetor off at least 5 times now, modded the airbox, and currently waiting on a jet kit/spark plug to arrive from Amazon. As of now I daytrade stocks and fix computers, recently decided I wanted to learn trading, so far one job is financing the other, I'm sure you can guess, I am getting better though.

I've soaked up quite a bit of info on mods for the Hawk and decided I'd delve a bit deeper into the combustion process and how I can enhance it. I came across some goofy looking plug called an E3 something, it claims to increase all kinds of good stuff, I stared at it for a minute and called bs on those claims. This got me searching for the sciency parts, not the "it runs so much better now" reviews. There's no way this plug can help, and now I know why. I'll get you started with some actual data acquired by proper experimentation.

http://www.sciencedirect.com/science...90447912000883
The link looks a bit weird, I guess we'll see if it works once this is posted.

I'll give some facts I've learned on the subject up front, the article is a bit lengthy. The abomination called the E3 spark plug looks like someone welded half a thimble onto the sparky end of it. I'll try to link it here.
https://www.amazon.com/E3-Spark-Plug-E3-36-Powersports/dp/B0022ZAFOC/ref=sr_1_5?ie=UTF8&qid=1477232338&sr=8-5&keywords=e3+spark
First off I'll give you some info on what's called "flame quenching", this is the effect of the cooler spark plug electrode and ground strap interfering with flame propagation at the exact point of ignition in your compressed air/fuel charge. Spark plugs do a very good job of conducting their heat into the engine block, this happens so your next incoming charge doesn't hit a bright white hot spot of metal and ignite before it's supposed to, also it keeps your spark plug from melting and introducing new parts to your engine you'd rather not have. The spark from your electrode tip to the ground strap is very small and takes the shortest path with the least amount of resistance, go ahead and put those advertisement pictures out of your mind, the ones that look like a ball of plasma forming around the electrode and ground strap, or the ones with 2 to 4 neatly arranged ground straps. The first point of ignition once the spark leaps from the electrode to the ground is a tiny little area between the two, combustion begins here and propagates outward, some of it's energy needed to cause a reaction in the surrounding particles is absorbed into the cooler ground strap and electrode, slowing this process and causing an uneven shockwave to form outward from this point until all air/fuel is reacted. What you really want is that explosion to travel equally outward with nothing in the way to absorb it's energy or break up it's wavefront as that ends up burning your fuel slower, which causes it to lag behind the perfect crank position to give you maximum cylinder pressure on the downward power stroke. The position at which the combustion begins should be as close to center of it's surrounding volume as possible for best results in efficiency and power. This is why you see spark plugs with the longer electrode end, it gets the spark closer to the optimal chamber position for ignition.

There's more! You don't need colder series plugs unless you're running forced induction or other means of extreme cylinder pressure. A colder plug transfers cylinder heat "energy" into the head faster than a warmer plug. With higher pressures you have higher temperatures, the colder plug is designed to keep the ground strap/electrode from melting in a more extreme environment, and pre-detonation. Very few setups benefit from a colder spark plug. A cold plug will also foul out quicker as it isn't hot enough to burn off the residue remaining from the combustion cycle, causing some to think they are running the engine too rich when inspecting the spark plug.

Finally to the spark. Electricity always takes the path of least resistance. A generic or standard spark plug normally has a decent sized round flat electrode and flat square ground strap, they call this the J plug/design. The electrode end needs to be a certain size depending on it's properties "iridium/platinum/cheapium" to survive cylinder temperatures without melting. The more exotic metals have a higher melting point, this allows them to be smaller, which increases flame propagation area, and lowers surface area to decrease electrical resistance for the spark jump. Resistance also increases along with higher atmospheric pressure, aka, your compressed fuel charge.

I think you've got the bulk of the info, now for the fun stuff. You can sidegap your spark plug by cutting back the ground strap, opening up the ignition area for a more optimal burn. The power of your ignition, pressure in your cylinder, and resistance of the electrode material determine how wide you can set your gap. The electricity builds up on the end of the electrode until it can overcome it's surrounding resistance then jumps to the nearest ground. A wider gap creates a longer spark and a larger initial ignition area, too wide and it may fail to spark or slightly delay until it can overcome it's surrounding resistance. Cool stuff huh. A little experimentation for possible increased efficiency and power can't hurt, right? Plugs are cheap to replace if one happens to expire during clinical trials!

You can also completely cut off the ground electrode, some plugs are made this way, they are called flat gap plugs, the above linked test results show this plug type performing above all others in it's ability to create higher cylinder pressure due to quicker/more even flame front. I know, it sounds crazy to cut off the little J ground strap completely, and I wouldn't advise anyone to immediately go out and do this unless they have a backup plug. Back to the spark travel and resistance I talked about earlier, if the electrode is sticking out pretty far past the base of the plug where it needs to ground the spark will travel along the outside surface of the ceramic material under the electrode before jumping to the ground, ceramic may be an insulator yet electricity encounters lower resistance along it's surface than the surrounding air until it reaches the shortest route to the ground, so it will spark. Wall of text, sorry if anyone has fallen asleep attempting to read this. Hell of a first post though.

[Jmcgee]

I have some "Race only" plugs without the electrodes/ground straps on them, never used them in my ninja but I was going to till it broke. I was told they were slightly longer and grounded to the piston. Never measured them and have no idea why they are labeled race only....

[BlackBike]

As someone here calls it, I skim read it. Nice! So your next task is to figure out how to post some of those modifications on the plugs in the form of ....pictures.

Cavemen like pics!

[BlackBike]

Originally Posted by Jmcgee

I have some "Race only" plugs without the electrodes/ground straps on them, never used them in my ninja but I was going to till it broke. I was told they were slightly longer and grounded to the piston. Never measured them and have no idea why they are labeled race only....

Probably unreliable and stall at idle, only good at constant and higher rpm s I would guess.

[Ghenghis]

Soon as I mutila...... modify a plug I'll post a picture up here with my results.

Does the seat on the Hawk seem like it would be better if it dipped down just a bit more in the middle to anyone else? Height isn't a problem, I'm 6'2", it just seems like i'm sitting a bit high.

Edit:I'll try shortening the J strap on the stock plug first and see if I get any noticeable differences. I should probably get it running smooth first. I pulled the carburetor, took it apart, adjusted the idle mix screw, now it bogs at half throttle right when the main jet is kicking in. Unsure if it's starving or too rich, haven't spent much time on it yet. I've tried anywhere from 1 turn out to 2 turns out, it seems to lessen the stumble/bog at 1 turn out but doesn't get rid of it. Ran fine after putting it together from the shipping crate, I'm sure the bogging is from something I did while removing the carb and tearing it apart.

[Ghenghis]

Originally Posted by Jmcgee

I have some "Race only" plugs without the electrodes/ground straps on them, never used them in my ninja but I was going to till it broke. I was told they were slightly longer and grounded to the piston. Never measured them and have no idea why they are labeled race only....

That sounds a bit too close to the piston, I'd be afraid of those. And if they're labeled as race plugs then they aren't suitable for normal use, plenty of small changes they'll make to those plugs tweaking them to work best in certain situations. Some of them are designed to intentionally melt certain parts if cylinder temps are dangerously high from accidental lean or detonation conditions. It said they'll just foul out after this, killing the plug but saving your piston from melting.

[Ariel Red Hunter]

Originally Posted by Ghenghis

Bought a Hawk 250 a couple months ago, red with black rims, reading posts from here and watching MotoCheeze's videos won me over.

I had a late 70's Yamaha 125 Enduro a long time ago, got it used when I was 13, learned how to replace and adjust the points/condenser I ordered out of the JC Whitney catalog as it would hardly run when I got it. Crazy to think that we had to actually ask someone, usually a friend's mechanic dad, or an uncle, how to fix things. I rode the wheels off that bike, the wheels never actually came off but the muffler began to form rust holes on the outer skin. Had to leave it behind when we moved from the country into the city, it had broken down so I didn't get much say in the matter. I've always wanted to get another Enduro, the ability to do some light off-roading and legal street driving always seemed like a win win.

Finally, nearly 30 years later I decided to get another Enduro. I've always had an interest in anything mechanical, I had to know how it worked, and what I could do to make it better. I'm an information sponge, so I know at least a little bit about everything. My Hawk doesn't have 20 miles on it yet and I've had the carburetor off at least 5 times now, modded the airbox, and currently waiting on a jet kit/spark plug to arrive from Amazon. As of now I daytrade stocks and fix computers, recently decided I wanted to learn trading, so far one job is financing the other, I'm sure you can guess, I am getting better though.

I've soaked up quite a bit of info on mods for the Hawk and decided I'd delve a bit deeper into the combustion process and how I can enhance it. I came across some goofy looking plug called an E3 something, it claims to increase all kinds of good stuff, I stared at it for a minute and called bs on those claims. This got me searching for the sciency parts, not the "it runs so much better now" reviews. There's no way this plug can help, and now I know why. I'll get you started with some actual data acquired by proper experimentation.

http://www.sciencedirect.com/science...90447912000883
The link looks a bit weird, I guess we'll see if it works once this is posted.

I'll give some facts I've learned on the subject up front, the article is a bit lengthy. The abomination called the E3 spark plug looks like someone welded half a thimble onto the sparky end of it. I'll try to link it here.
https://www.amazon.com/E3-Spark-Plug...words=e3+spark
First off I'll give you some info on what's called "flame quenching", this is the effect of the cooler spark plug electrode and ground strap interfering with flame propagation at the exact point of ignition in your compressed air/fuel charge. Spark plugs do a very good job of conducting their heat into the engine block, this happens so your next incoming charge doesn't hit a bright white hot spot of metal and ignite before it's supposed to, also it keeps your spark plug from melting and introducing new parts to your engine you'd rather not have. The spark from your electrode tip to the ground strap is very small and takes the shortest path with the least amount of resistance, go ahead and put those advertisement pictures out of your mind, the ones that look like a ball of plasma forming around the electrode and ground strap, or the ones with 2 to 4 neatly arranged ground straps. The first point of ignition once the spark leaps from the electrode to the ground is a tiny little area between the two, combustion begins here and propagates outward, some of it's energy needed to cause a reaction in the surrounding particles is absorbed into the cooler ground strap and electrode, slowing this process and causing an uneven shockwave to form outward from this point until all air/fuel is reacted. What you really want is that explosion to travel equally outward with nothing in the way to absorb it's energy or break up it's wavefront as that ends up burning your fuel slower, which causes it to lag behind the perfect crank position to give you maximum cylinder pressure on the downward power stroke. The position at which the combustion begins should be as close to center of it's surrounding volume as possible for best results in efficiency and power. This is why you see spark plugs with the longer electrode end, it gets the spark closer to the optimal chamber position for ignition.

There's more! You don't need colder series plugs unless you're running forced induction or other means of extreme cylinder pressure. A colder plug transfers cylinder heat "energy" into the head faster than a warmer plug. With higher pressures you have higher temperatures, the colder plug is designed to keep the ground strap/electrode from melting in a more extreme environment, and pre-detonation. Very few setups benefit from a colder spark plug. A cold plug will also foul out quicker as it isn't hot enough to burn off the residue remaining from the combustion cycle, causing some to think they are running the engine too rich when inspecting the spark plug.

Finally to the spark. Electricity always takes the path of least resistance. A generic or standard spark plug normally has a decent sized round flat electrode and flat square ground strap, they call this the J plug/design. The electrode end needs to be a certain size depending on it's properties "iridium/platinum/cheapium" to survive cylinder temperatures without melting. The more exotic metals have a higher melting point, this allows them to be smaller, which increases flame propagation area, and lowers surface area to decrease electrical resistance for the spark jump. Resistance also increases along with higher atmospheric pressure, aka, your compressed fuel charge.

I think you've got the bulk of the info, now for the fun stuff. You can sidegap your spark plug by cutting back the ground strap, opening up the ignition area for a more optimal burn. The power of your ignition, pressure in your cylinder, and resistance of the electrode material determine how wide you can set your gap. The electricity builds up on the end of the electrode until it can overcome it's surrounding resistance then jumps to the nearest ground. A wider gap creates a longer spark and a larger initial ignition area, too wide and it may fail to spark or slightly delay until it can overcome it's surrounding resistance. Cool stuff huh. A little experimentation for possible increased efficiency and power can't hurt, right? Plugs are cheap to replace if one happens to expire during clinical trials!

You can also completely cut off the ground electrode, some plugs are made this way, they are called flat gap plugs, the above linked test results show this plug type performing above all others in it's ability to create higher cylinder pressure due to quicker/more even flame front. I know, it sounds crazy to cut off the little J ground strap completely, and I wouldn't advise anyone to immediately go out and do this unless they have a backup plug. Back to the spark travel and resistance I talked about earlier, if the electrode is sticking out pretty far past the base of the plug where it needs to ground the spark will travel along the outside surface of the ceramic material under the electrode before jumping to the ground, ceramic may be an insulator yet electricity encounters lower resistance along it's surface than the surrounding air until it reaches the shortest route to the ground, so it will spark. Wall of text, sorry if anyone has fallen asleep attempting to read this. Hell of a first post though.

The need for "hot" and "cold" spark plugs went pretty well away when manufacturers went from Cast Iron cylinder heads to aluminum. Aluminum has much better heat flow than cast iron. That means it responds to temperature changes much more quickly. The next big deal was when NGK developed a much more multi-range spark plug. The current hot set-up is Iradium spark plug electrodes. The no ground electrode was tried in this country in the 1960's and seventies. They really worked in two-stroke engines, especially on leaded gasoline. I had an Evinrude v-four outboard that those "surface-gap" plugs really worked in.

[Jmcgee]

When we were racing back in the 80's we would index our plugs (put the gap facing the valves) It was supposed to make more power/more efficient combustion. I couldn't tell if it did or not, but a whole lot of little things that are micro increases is what tweaking an engine is all about

[kohburn]

if you want some interesting spark plugs to analyze, check these out


https://www.amazon.com/dp/B00NAH39NA...=IROW6N3EOJEN6

[BlackBike]

Originally Posted by kohburn

if you want some interesting spark plugs to analyze, check these out


https://www.amazon.com/dp/B00NAH39NA...=IROW6N3EOJEN6

Will you give that a go in the tt? Be sure to calibration the seat/pants dyno

[Ghenghis]

Sorry for the long delay, I've been busy with other projects. I finally found some time to do my first modification to the stock plug. I've been trying to fine tune the PZ30 carb and having a hell of a time doing so, it keeps dying while I'm riding it, wait 1 minute and it starts back up, I'm guessing the gas cap isn't letting air in, I'll fix that tomorrow, then adjust the valves.

I think I've just about got all the kinks worked out so the plug tests will come soon. Here is a pic of the first test subject, it hasn't been gapped in the picture, it's now gapped to 0.7mm. I'll also try different variations on indexing the plug, once I have some results I'll move on to modifying the NGK iridium plug.[IMG][/IMG]
Anyone have a schematic or any idea on how much plug to piston clearance these engines have?