<div class="FTQUOTE"><begin quote>But my question is still hanging in the air.... What happens when a hot plug + a lean condition + hard riding??? </end quote></div>

It is my understanding that using a plug of too hot a heat range for operating conditions can lead to pre-ignition and detonation.

 

<div class="FTQUOTE"><begin quote>Originally posted by: JeffinTD

<div class="FTQUOTE"><begin quote>But my question is still hanging in the air.... What happens when a hot plug + a lean condition + hard riding??? </end quote></div>



It is my understanding that using a plug of too hot a heat range for operating conditions can lead to pre-ignition and detonation.</end quote></div>


Yes, me too, that's why I'm wondering what Honda is on about in their manual.

 

I will keep buying Yamaha's. They never start in cold weather, and that way I do not have to worry about how much heat the sparkplug difuses.......Don't shoot, I love my Yammies

 

The more I think about it, Ive realized that the dry foul is just the symptom, not the cause. Like having a backache caused by cancer. If you make the backache better, (the symptom), the desease is still there. The problem hasnt been solved, the underllying cause is still there.
I think we are both on the same track,Gimpster, that plugs can foul(symptom), because the head disapates heat so quickly(cause), that there isnt enough heat for the plug to burn off deposits. But i view the dry foul as a symptom, and not the cause. Changing the spark plug back to a stock plug will foul again. And actually going to a hotter plug, takes care of the symptoms too, but for a longer time. There isnt really a fix for the cause, because that would effect summer riding, so its just a temporary fix, so the atv can be used in cold weather.
There is a reason why the water cooled engines dont need a plug change, yet the information on air cooled engines suggest you do. I think it has to do with the water cooled motors shed the same rate of heat, winter or summer, because of the water jacket, and the thermostat,...leaving the spark plug the same amount of heat to disipate all year long, and burning off the deposits no matter what the temperture is..
Theres alot of information out there on air cooled airplane motors, and the need for hotter plugs, but not very much information as to why. Ill keep looking, but the best info I could find was in my clymers, for the 400ex, for why the plug needs to be a hotter heat range for winter use. The honda service manuals, are good, but very light on theory.
Cmarti, Ive got a 450 kodiak, thatll start anytime I want it to,even down to -10F and its got to be one of my most reliable starters [img]i/expressions/face-icon-small-smile.gif[/img]

 

Today I was riding pretty hard in 40 degree temps. Engine was hot enough to smoke the oil that is leaking off my cooling fins. Plug looks pretty good. Very light tan.... All the way down as far as I can see. I don't think its lean, but its close. I sanded about .004 off the last half inch or so of my needle. That seemed to make the mixture a little more uniform from half to full throttle.

The plug it stock. The engine is air cooled. My symptom is lean. My strategy was to richen the last half of the throttle opening.

 

A quick fix involves using duct tape. Just gradually cover the snorkle opening a bit at a time, and somewhere around 1/3 to 1/2 of the opening will richen it up. That way you dont have to deal with ice cold stuff, like carbs and float bowls and jets.
Its kind of a macgiver fix, but its effective, and easy to set back to stock for a warm day.

 

Seems like the degree of richness would go up exponentially by choking off air flow. IE. at low throttle there would not be much air flow resistence, but at WOT there would be a lot of air flow resistence. You might still be lean at idle and very rich at WOT.... and somewhere in the middle be right. IMO anyway.

 

<div class="FTQUOTE"><begin quote>Originally posted by: hondabuster

The more I think about it, Ive realized that the dry foul is just the symptom, not the cause. Like having a backache caused by cancer. If you make the backache better, (the symptom), the desease is still there. The problem hasnt been solved, the underllying cause is still there.

I think we are both on the same track,Gimpster, that plugs can foul(symptom), because the head disapates heat so quickly(cause), that there isnt enough heat for the plug to burn off deposits. But i view the dry foul as a symptom, and not the cause. Changing the spark plug back to a stock plug will foul again. And actually going to a hotter plug, takes care of the symptoms too, but for a longer time. There isnt really a fix for the cause, because that would effect summer riding, so its just a temporary fix, so the atv can be used in cold weather.

There is a reason why the water cooled engines dont need a plug change, yet the information on air cooled engines suggest you do. I think it has to do with the water cooled motors shed the same rate of heat, winter or summer, because of the water jacket, and the thermostat,...leaving the spark plug the same amount of heat to disipate all year long, and burning off the deposits no matter what the temperture is..

Theres alot of information out there on air cooled airplane motors, and the need for hotter plugs, but not very much information as to why. Ill keep looking, but the best info I could find was in my clymers, for the 400ex, for why the plug needs to be a hotter heat range for winter use. The honda service manuals, are good, but very light on theory.

Cmarti, Ive got a 450 kodiak, thatll start anytime I want it to,even down to -10F and its got to be one of my most reliable starters [img][/img]</end quote></div>

I suppose the fuel will burn slower in colder weather, bigger fuel droplets not mixing with the cold air. What I was leaning to would be in theory, the fuel burning more towards the pipe side than in the cylinder side during valve overlap, drawing heat away from the combustion chamber, and not really preheating the fuel coming in from the intake. A hotter plug would (as mentioned in the link) raise the cylinder tempurature with it's ability to disipate more heat from combustion to the head. Wouldn't this gain back some of the heavier fuel droplets ability to mix upon entry to the intake valve ?
Without changing the spark plug, I believe detonation (not to be confused with pre-detonation) is what is keeping the cylinder so hot, fan running more from heat the detonation is causing. I did not see this mentioned on the NGK site, I was learned that detonation causes dry foul by coating the spark plugs insulating tip so spark will more readily follow a path down the insulator to the plugs ground at the base of the plug. Electricity is lazy. Easier for it to follow a dry coated insulator to ground than to jump the gap of the plug.
A colder spark plug in the given low temps will be actually hotter at the tip than a hot plug in this way... It will not disipate as much heat into the cylinder head as fast as the broader tip depth of a hotter spark plug, hence promoting a higher chance of damaging detonation in cold weather, high humidity weather.

Is anybody still confused....[img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/beer.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img] ... hehehe

----- Gimpster -----

 

And yes, the liquid cooled models do have a more controled head heat because of the liquid within.

----- Gregg -----

 

Yeah, I'm a bit confused still... but slowly settling down on my own theory. I still think your fans come on because the engine is running lean. Also, the density goes up as temps drop, so I think compression goes up too, which yields more heat. I don't think detonation plays a significant role. If it exists, it would be small and barely existing,,, and I think you would have to hear a knocking sound coming from the engine. Detonation is just a fancy way of saying there are two or more wave fronts caused by explosions. When the wave fronts meet, there should be a sound. Anyway, something would have to set in motion the second front (ie a hot piece of carbon or a hot spark plug).

The NGK website says the colder plug dissipates more heat; hence, stays cool. This is where I'm still confused.