<div class="FTQUOTE"><begin quote>Originally posted by: hondabusterSounds to me like you have problems to deal with, whats with the attitude?</end quote></div>

So, you took that as some kind of personal attack did you??? My point was that one has other mechanical problems (besides the plug itself!), if they are fouling 4-stroke plugs.......

 

I guess I'd have to disagree.

I know from personal experience that constant short runs (say -20 where the motor never gets up to operating temp) can foul the plug on a 4 stroke that has no mechanical problems.

You asked about the need to run a hotter range plug, and hotter plugs are intended to run warmer to burn off deposits and thus resist fouling...

Since you are talking about running occasionally down into the teens, I don't doubt you have never had a plug foul...

 

The point of running a hotter plug is to keep the combustion chamber at the proper temperature, plain and simple. That happens to keep the plug from fouling, so all is well and good!

 

Yeah, exactly. I don't think you will have trouble since you will likely be running the machine long enough for it to get to operating temp and stay there for a bit.

 

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

The point of running a hotter plug is to keep the combustion chamber at the proper temperature, plain and simple. That happens to keep the plug from fouling, so all is well and good!</end quote></div>

Wrong.
The fuel mixture regulates the combustion chamber temperature.
Once more.....the spark plug adds NO heat to the process, spark plugs only REMOVE heat. The rate at which they remove heat determines whether it is a relatively hot or cold plug.

 

NGK Heat range explained

Here is some food for thought
Winter - pushing snow with my Foreman 450 the fan never stops running outside temps from 0 to 30 degrees. I foul plugs... hmmmm
Summer - pushing gravel or dirt my fan rarely runs. outside temps ranging from 70 to 100 degrees, no plug foul

DPR8EA9 spark plug both temp ranges (winter - Summer)

Backwards ?? (riddle me this)

I will tell you when someone nails the reason why it seems backwards


----- Gimpster -----

 

The colder it gets here, the leaner my quad runs. In the summer, my plug looked ok, but I looked today and it was bright white. The thought actually crossed my mind to use a colder plug, lol. But I put in a larger main jet and its still white on the ground strap, but not as bad.

I have no clue why engineers say to use a hotter plug. Reminds me of something Mark Twain said, "Don't read too many health books, you may die of a misprint!"

My logic goes like this: The cold air is dense air and when mixed with gas, the ratio of air particles to gas particles goes up per constant volume. So, if we have too many air particles, we are too lean. Why use a hotter plug in a lean condition?

Given that the manual is not a misprint and the engineers were not drunk at the time, I would say that using a hot plug in winter is something special to that quad and not a general "rule of thumb". Maybe there is a fuel management issue that over richens the mixture when its cold out for reliability reasons. That would explain the 450 fouling plugs in the winter. That would also explain having to use a hotter plug.

 

I was thinking along the same lines, that denser colder air, plus gasoline's tendency to not vaporize into as small a particle could tend to cause the mixture to go slightly lean... which would result in an increase in combustion chamber temps...

Generally, I've been told to run a hotter plug in cold weather, but maybe that only applies to EFI systems, which would automatically compensate for temp or air density to maintain proper mixture... In which case one would guess that the colder incoming air would lower combustion chamber temps?

Quads don't have a system to draw manifold heated air into the carb during cold weather, the way the old carburated cars were set up.

 

<div class="FTQUOTE"><begin quote>Originally posted by: JustRandyI would say that using a hot plug in winter is something special to that quad and not a general "rule of thumb".</end quote></div>

In the original post, I gave a list of my machines (Rancher 350 and 250EX). At no time did I ever say anyone should run a hotter plug if their owner's manual doesn't recommend it!!! Wouldn't matter though, most folks have never even opened their owner's manuals anyway....so they are oblivious!

Looking at the manuals for my other machines, the TRX90 also has a recommendation for a hotter plug in cold weather. I didn't list it, because we would never take the little kids out in cold weather anyway.

My Rancher 420 (EFI) does not require a plug change with temperature.

Interesting, the 450R and 400EX recommend a colder plug for "continuous high speed riding", but do not recommend a hotter plug for cold weather.

So yes......it all depends on the individual machine!

 

very good points you guys

Recon you are right most people never bother to crack the owners manual.
Gimpster thanks for that link.