Using a B9ES Plug for summer...

[salty_monk]

Wondering whether to switch to a cooler nine plug from the stock 8 for Summer this year.
I'm going to Baja & we are likely going to hit 100 degrees plus at some point - nothing I haven't done before with the 8 plugs but I'm thinking that it might help with oil temps etc.

Any thoughts? Any of you desert dwellers tried it?

[rapidray]

Dan, as long as you have adjusted the mixture screws CORRECTLY, the colder plugs will help. Ray.

[trippivot]

excellent IDEA! a B10 is not unheard of in the desert heat.

You may not have to readjust the fuel mixture.. You will need to go a little longer on the enrichener. The warm up will take a few seconds (minutes) longer.
throttle response while cold is the biggest change you'll notice. be sure not to attempt to re-tune until it is HOT or you'll be chasing a non issue.

[BassCliff]

Hi Dan,

I have no direct experience but I did some quick research on spark plug heat ranges. One of the suggested uses of cooler plugs is as you describe, to lower engine and oil temprature. You probably want to keep a set of stock plugs handy just in case your bike starts acting too funky with the cooler plugs.

All the best to you and yours,

Cliff

[Steve]

I am somewhat surprised by the answers already given, especially considering who offered them.

Please keep in mind that the spark plug is not like a thermostat, it does NOT control how hot the engine burns. With no other changes, simply inserting a "colder" plug will only let the plug foul up quicker, because it is not getting hot enough to clean itself.

If you want to cool your engine a bit, richen up your mixtures a touch, for cooler combustion. However, if you do that and use a "colder" plug, the plugs will definitely foul up.

.

[Nessism]

I'm with Steve: since when does changing the heat range of the plug effect the engine temperature?

Using a hotter than stock plugs is a good idea when the existing plugs are getting fouled - the hotter plug will help burn off deposits thus reducing the fouling tendency. If the plug is too hot though, it will melt and fail as a result. Running though the desert where the temps are killer hot the regular plugs may fail because of melting so in this instance it would be a good idea to move to a cooler plug, not to reduce engine temp, but to extend the life of the plugs themselves.

[chuckycheese]

Don't

I've discussed this very issue with several people who make their livlihood working on old Japanese motorcycles and they all have said it's a bad idea.

[Nessism]

Using a non standard heat range plug will not hurt the engine in the least. But it may hurt YOU when you have to push your bike home because the plug failed.

[7981GS]

The higher the heat range of the plug, the longer it takes to transfer the combustion heat to the cylinder for cooling.
The plug stays hotter and can actually cause pre-ignition.
Dan, you will be fine using a colder plug.

Daniel

[BassCliff]

Hi,

This is the reason for my thoughts on the matter:

From http://www.totalmotorcycle.com/maint...sparkplugs.htm

Hot and Cold Sparkplugs

Tip: It is better to fix the problem than to change the sparkplug to patch it up.

Why Hot and Cold Sparkplugs? Using a hotter or colder sparkplug can be just the fix to an engine problem. Very basely, if your motorcycle engine is running hot then try using a colder plug, if it is running hot try a colder plug.

NGK diagram showing insulator and heat range

Hot Plug

- has a longer insulator nose length
- less heat is absorbed by the plug and transferred to the cooling system
- the plug runs at a higher temperature
- the plug is more prone to pre-ignition (if greater than 850 degrees C)
- NGK BP5ES is hotter than a BP7ES plug.
- An overheated plug will be white with brown spots.

Cold Plug

- has a shorter insulator nose length
- more heat is absorbed by the plug and transferred to the cooling system
- the plug runs at a lower temperature
- the plug is more prone to fouling (if less than 500 degrees C)
- NGK BP7ES is cooler than a BP5ES plug.
- A fouled plug will be black and sooty.
******************************

Howstuffworks.com says...

Some cars require a hot plug. This type of plug is designed with a ceramic insert that has a smaller contact area with the metal part of the plug. This reduces the heat transfer from the ceramic, making it run hotter and thus burn away more deposits. Cold plugs are designed with more contact area, so they run cooler.

The carmaker will select the right temperature plug for each car. Some cars with high-performance engines naturally generate more heat, so they need colder plugs. If the spark plug gets too hot, it could ignite the fuel before the spark fires; so it is important to stick with the right type of plug for your car.
*****************************


Thank you for your indulgence,

BassCliff

[Steve]

Yeah, we know how they work, but the bottom line is that changing the plug will not make the engine run any cooler.

.

[salty_monk]

I thought it would start a debate...

Thanks for all the comments so far...