Gimpster, good question, and my foreman is the same. Ill pull the kids around in the sled, and even on very cold days, the fan comes on. Yet all summer, slogging thru the mud, it didnt come on once.
My guesss, is like the others....the mixture leans out in the cold dense air, and the combustion temps are up. The plugs foul easier, because of the primer use and choke use, on cold starts?

 

Well, I don't know much about Honda's EFI machines, so i was just taking a shot in the dark.... It seems to fit Honda's "personality" to address rideability and reliability by slightly overly richening the mix in cold weather. This makes for easier starts and heads off any lean conditions. But all that is just speculation on my part.

I have a 250ex, but I don't have a manual and don't ride it that much anyway. It doesn't have an efi, so I am shocked that it would require a hotter plug in the winter. [img]i/expressions/face-icon-small-shocked.gif[/img] I can tell you this much though... Its a PITA to start and takes forever to warm up so someone else can ride it (like kids or the ladies that have no clue about chokes n carbs).

I have a bayou and I have the service manul for it. I don't remember anywhere it saying to change plugs for any reason. In cold weather I apply the choke and it fires right up. Let off the choke and ride and never have a problem. I have a plow on it that I use to plow dirt and trees,,, keeping my trails in good condition for riding my quadsport. ... and it gets hotter in the summer. I usually go plowing right after it rains when the ground is soft and the air is cool.

I have a 230 quadsport that no one has seen the owner's manual in decades. I just paid $70 for the factory service manual and don't remember seeing any plug change recommendations. I've also rebuilt it and added a larger carb. It starts fine in cold weather and runs right away like the bayou. Like I said earlier though, it does run lean when its cold outside, but I've never really noticed the engine being extremely hot. However, I can only ride it about 20-30 minutes at a time because my arms in shoulders wear out way before the engine ever gets tired. [img]i/expressions/face-icon-small-tongue.gif[/img]

I don't know if its true or not, but I've read somewhere that gas doesn't want to burn at extremely cold temps, ie -40, and you can actually put a match out in it. Maybe this has something to do with the plug change recommendations...? This is looking like a puzzle that will take someone with more knowledge of thermodynamics than myself to fully explain.

I think most people do not read their owner's manuals for one of two reasons: 1) they just spent a small fortune on a new quad and expect it to "just work",,, and in case it doesn't "just work" they have a warranty. 2) they got it used and the original owner has lost the manual long ago.

 

This topic has been a good read and will get better.
Notice how I linked to the second page ?
If you read page 1 and page 4, the answer I am looking at can be figured out.
Another hint would be the fact that people are mislead when it comes to hot and cold ranges of a spark plug. Higher tip temps of a spark plug are obtained with a colder spark plug, where a hotter spark plug disipates more heat to the cylinder head and in turn has a cooler tip temp.
Yep, colder weather will make the cylinder lean.
Choke and primer in cold weather can add to plug fouling
My question and Recon's origional question share the same answer

----- Gimpster -----

 

After thinking awhile, Its probably got to do with the air cooled head. The fins are large, and designed to disapate a large amount of heat, and they probably error on the side of safety, and long engine life, so the fins do a very good job in summer. But when the temps get really cold, there is too much transfer of heat, and there is less for the spark plug to disapate....hence the need for a hotter plug, which disapates slower, and keeps the plug clean.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Gimpster
Another hint would be the fact that people are mislead when it comes to hot and cold ranges of a spark plug. Higher tip temps of a spark plug are obtained with a colder spark plug, where a hotter spark plug disipates more heat to the cylinder head and in turn has a cooler tip temp.

----- Gimpster -----</end quote></div>

ok, the page you linked to says the cold plug's tip does not heat up quickly. ...and I'm taking "quickly" to mean "easily". Therefore, the cold plug is colder at the tip. So, I'm confused. [img]i/expressions/face-icon-small-confused.gif[/img]

Here's a quote from page 3: "This means the plug has a higher internal temperature, and is said to be a hot plug. A hot spark plug maintains a higher internal operating temperature to burn off oil and carbon deposits, and has no relationship to spark quality or intensity."

"Conversely, a cold spark plug has a shorter insulator nose and absorbs more combustion chamber heat. This heat travels a shorter distance, and allows the plug to operate at a lower internal temperature. A colder heat range is necessary when the engine is modified for performance, subjected to heavy loads, or is run at a high rpm for a significant period of time. Colder spark plugs remove heat quicker, reducing the chance of pre-ignition/detonation."

 

Real good points you guys !

So the way we look at it, Reconranger's manual calls out for a HOTTER plug when the ambient temp DROPS below 41 degrees ambient temps.

My Foreman's fan runs more than normal in freezing temps

SOO...

In theory, since we came to the conclusion that colder air makes the mixture leaner (engine will run hotter), wouldn't we want to install a colder plug to disipate the heat built from lean mixture of the engine ?

Then ask yourself, once again, why are they calling out for a hotter spark plug and no jet change ?

( I think I will have to go back to the link again and reread the part about ambient temps and humidity)

hmmmm, were getting closer to the answer [img]i/expressions/face-icon-small-confused.gif[/img] yet?

----- Gimpster -----

 

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

In theory, since we came to the conclusion that colder air makes the mixture leaner (engine will run hotter), wouldn't we want to install a colder plug to disipate the heat built from lean mixture of the engine ?

----- Gimpster -----</end quote></div>

Actually, I'd rather jet up to get more power. [img]i/expressions/face-icon-small-happy.gif[/img]

I think you're just going to have to explain your theory before everybody loses interest, lol....

 

hehehe

I will soon

Like I said before, you guys ARE good

I'm not playing games, this topic IS a mind twister

(I would rejet also)

----- Gregg -----

 

While cold air is more dense and you end up slightly leaner, for the average rider the effect won't be enough to warrent a rejet. I mean hey, you guys don't even want to do an extremely simple plug change....much less a rejet.

 

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

While cold air is more dense and you end up slightly leaner, for the average rider the effect won't be enough to warrent a rejet. I mean hey, you guys don't even want to do an extremely simpe plug change....much less a rejet.</end quote></div>


I would do the plug change, but that wouldn't give me anymore power. A jet change will. ... and I also get a chance to lube the cables and moving parts in the carb. But I doubt a "normal" person would ever want to do all that! [img]i/expressions/face-icon-small-tongue.gif[/img]

I did a google on the words "hotter plug winter" and "hotter plug cold weather" and read a few pages (some of them are glow plugs, so watch out!). They all seem to agree,,, install a hot plug in winter if you have hard starting AND don't run it very hard for very long AND the engine must be stock. Rarely would you ever want a hotter plug than what the manufacturer recommends. However, if you have a "built" engine you may want to go colder.