Both my Rancher 350 and 250EX's recommend a change to a hotter spark plug when the ambient temperature drops below 41 degrees F.

http://www.ngksparkplugs.com/t...plugs/p2.asp?mode=nml


Trouble is, a lot of the low altitude rides we take will have a night time temp in the teens or 20's, but a daytime high in the 50's or higher. What am I supposed to do, stop in the middle of the day and change plugs???

What do you all think? Is it better to just ride all day with the standard plug, or ride all day with the hotter one??? (High altitude rides tend to be colder all day, so I would go with the hotter plug all the time in that case.)

 

I know in Alaska, where it gets to -20 and 30 below, that people just keep using the same plugs they use in the summer, here in MN too.
Spark plugs create no heat, they only remove heat. A hotter plug just removes heat slower than a cooler plug. I run the same spark plug all year long on all my motors.

 

Reconranger, unless you are doing short runs in cold weather, or running in consistantly very cold temps I wouldn't worry about it.

The worst thing that might happen is a fouled plug, so having spare plugs on hand might not be a bad thing, but other than that I wouldn't worry about it.

 

I tun a hotter plug than what came with the atv and I run it year round summer and winter without any problems

 

<div class="FTQUOTE"><begin quote>Originally posted by: hondabusterI know in Alaska, where it gets to -20 and 30 below, that people just keep using the same plugs they use in the summer, here in MN too.</end quote></div>

Doesn't surprise me....most folks have never even read their owner's manual! Most folks don't change to lighter oils for winter either.....

 

My point was that its unnecesary, not that they are ignorant. Even the spark plug companies, in their own literature,(http://www.ngksparkplugs.com/t...rk_plugs/techtips.asp) say the heat range only deals with burning off deposits. It has nothing to do with air temperature. Dont ask me why, the honda owners manual says to do that. My new civic doesnt have those instructions, and my old accord didnt either. Both start and run fine at 20 below, with the stock spark plugs. Even my old piece of crap chevy truck starts and runs fine with stock spark plugs.

 

At least a water cooled engine has a thermostat that helps regulate things somewhat, but when you are air cooled you are completely at the mercy of the ambient temperature to determine how much or how little you cool off the engine!

I think the idea is that cold air cools the engine off more, and the hotter plug just acts to transfer less heat out to the engine block to get carried away, thus helping to keep the combustion chamber at optimum temperature.

 

Same here I just leave the plug all year long, even on my old air cooled ATVs the engine was to hot to touch after a snow ride in 0 degrees F temperature.

 

You may have a valid point there reconranger. But ive never put in a hotter plug unless the motor was an oil burner, and i needed to burn the deposits off, better than the stock plug could.
But my experience has been, even on my 3 air cooled hondas, i just leave the stock plug in there year round.
Does the owners manual say to go to a cooler plug for hot weather?

 

Well, got to figure that those engineers (who designed the engine!) put that in the owner's manual for some reason! If you figure you know better than them, then do what you like.....