Basic Spark Plug Question

[350xBomb]

I was perusing the Honda 250r manual today and noticed that there are two recommended plugs: BR8ES and BR9ES. The 8ES is recommended for cold weather. What is the difference between these two plugs? And I use only a BR8ES, if I were to use I 9ES what changes would I see? Thanks.

[nouseforaname90]

I think that the 9ES has a hotter spark. Just stick with the 8.

[slothminx]

No cigar nouse heh;)

The number refers to the heat rating of the plug, this is the amount of heat the plug will conduct away using the ceramic nose. The cooler rated plug (higher number) will have a longer ceramic nose. The hotter plug (lower number) will have a shorter ceramic nose, sometime on really hot plugs recessed down into the plug.

A cooler plug may mean that the ceramic conducts too much heat away and there is a build up of deposits as they are not burnt off, this leads to fouling, Too hot a plug will not foul, but may not conduct enough heat away and will lead to pre detonation!.

You want the coolest plug you can run without fouling, this also depends on how you ride ;)

[sandpuppi101]

That's true sloth But... with the NGK plugs ,other brands such as Champion and what not ,are hotter plugs as the numbers go up,just to clarify !!

[mnnmaz]

off the subject but what is a powervalved TriZ? I use both and see no difference but I know the R is for resistor but who cares?

[mdunn]

Sandpuppi101 is correct. For domestic makers, the higher the number the hotter the plug. This is just the opposite for Japanese makers like NGK and Denso (ie the higher the number the colder the plug). Unless you have made significant changes to the engine, I would say you should stay with the stock plug.

[slothminx]

Yup, I should have said that was talking about NGK's thanks guys.

[350xBomb]

Thats what I needed to know. Thanks everyone.