friday i was workin on a raptor 660 that was back firing not ideling and would shut off unless the idel was very high. i took out the sparkplug and it was one heat range lower and still in good condition. we had the right plug on hand so i took a guess and but it in. it stoped backfiring and i lowered the idel and it was completely fine.so i think going down a heat range in the winter will cause problems or maybe it was just a bad plug.

 

I still think the biggest clue, or situation, is that liquid cooled motors dont have a spark plug change at low temps, but air cooled motors do. I would think everything(carburation, jetting, compression) would be the same, so that would eliminate them from being a factor.
I would think the reason to use a hotter plug, is to burn off the deposits and stop fouling. Honda must have figured the plug temps drop too far in colder weather, and thats why they suggest a hotter plug.
I reread those pages, and didnt come away with a different conclusion.
Ambient Air Temperature

As air temperature falls, air density/air volume becomes greater, resulting in leaner air/fuel mixtures.
This creates higher cylinder pressures/temperatures and causes an increase in the spark plug's tip temperature. So, fuel delivery should be increased.


Im sure the clue you want us to see is here, but im not making the link.
When this one is done....whats gonna be the next brain buster, teacher?

 

I have been thinking along the lines of dry foul. Once the plug dry fouls, and the user notes the unit will not start, they will pull the choke or pump the primer to gat it started. When they pull the plug it is wet. So the origional dry foul symptom is covered up.

Now thinking on the lines of dry foul, some of the info read into on the link may look a little different, or knowing dry foul is being avoided the info may be interpeted a little different to diagnos and cure the problem. To manipulate dry foul will take spark plug choice and cylinder temp control in a little different view than if you were under the assumption the plug was wet fouled when it was removed. So do you think Honda has addressed the issue of dry foul with a hotter plug ?

More food for thought, for sure.

Hondabuster -
Reading your posts, research and theories, I have learned a few things. Thanks


----- Gimpster -----

 

I suppose another variable to throw into the mix would be the oxygenated fuel we get in the winter here, to reduce air pollution when we are prone to stagnant air and occasional inversion. As I understand it that stuff also burns cooler.

The idea of glazing a plug under a high load high temperature situation would also be a possibility.

 

Well, so far, I've only seen a reason for a hot plug to get the engine started and run a bit longer than that. Once warm, however, it seems like a colder plug would be in order.

How did we get on the subject of dry fouled plugs???? I thought we decided an engine would run lean in the cold??? How would they foul?

Per the norm,,, I'm still confused. [img]i/expressions/face-icon-small-confused.gif[/img]

 

Thanks for the compliment, Gimpster and I enjoy and learn from reading your responses too.

Dry foul.....Im gonna have to think on that one. Im still bothered why its only the air cooled hondas, which are singled out for cold weather plug changes. The Rincon and 450r use the same plugs all year round. Honda motorcycles are that way too ....air cooled, its recommended, but not the water cooled ones. I would think the dry foul would happen on any engine, not just the air cooled ones.

 

my head hurts now......................too much thinking

 

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

Thanks for the compliment, Gimpster and I enjoy and learn from reading your responses too.



Dry foul.....Im gonna have to think on that one. Im still bothered why its only the air cooled hondas, which are singled out for cold weather plug changes. The Rincon and 450r use the same plugs all year round. Honda motorcycles are that way too ....air cooled, its recommended, but not the water cooled ones. I would think the dry foul would happen on any engine, not just the air cooled ones.</end quote></div>

The air cooled ones are jetted richer and/or have less compression than the water cooler ones. ... and I think the air cooled would lose its heat too fast when very cold outside. The water cooled would retain heat until the thermostat opened.

Therefore, the air cooled runs too cold for efficient combustion; hence the hotter plug.

But my question is still hanging in the air.... What happens when a hot plug + a lean condition + hard riding???

 

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



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

I dont think there is a hard and fast answer for that. One size doesnt fit all. Your definition of hard riding, may not be.However, I would think the hard driving would eliminate the need for a hotter than stock plug.
What I would do, is keep an eye on the spark plug. I would start with the stock plug, and see if it stays clean. It should, especially if youre driving it hard. If it shows signs of carboning up, then you can decide to go hotter, to burn it cleaner.
But if youre gonna ride it hard, and you want max preformance, Id think about jetting it richer for winter, one up on each jet should be more than enough.

 

All that sounds good.... Do you think Honda should qualify their statement by adding "unless you run it hard"? (or something like that)