Spark Plug heat ranges

When you guys go up & down with the spark plug heat range, what is it that you are trying to accomplish? Is this a speed thing or a ridability/startability thing? I never knew the purpose of this.

Tab

Re: Spark Plug heat ranges

Tabpat wrote:

>

> When you guys go up & down with the spark plug heat range,

> what is it that you are trying to accomplish? Is this a

> speed thing or a ridability/startability thing? I never knew

> the purpose of this.

>

> Tab

Its a heat thing and a plug fouling thing....

Generally you go to a colder plug when you modify the engine for more power (which can make them run hotter)... the spark plug removes a certain amount of heat from the combustion chamber... and a 'colder' plug removes more heat.., hotter.. less.

If you make an engine make a lot more power... 2 steps colder might be needed.

But for more normal mods... 1 step is enough.. (or stock might even be OK)

If your engine is stock.. the original heat range is fine.

I couldn't imagine going hotter on a stock engine... there is no reason.

On NGKs... 10 is cold, 9 is warmer, 8 warmer yet...and so on.

As a general guide... very high performance racing engines will run 9's or 10's.

Slow, low performance engines will run 5's or 6's.

Hot plugs burn off deposits (on the plug) left from slow running that will cause fouling.

A 5 or 6 run in a very high performance engine will melt a hole in the piston right at the spark plug.

A 9 or 10 run in a slow low performance engine will foul in no time.

Re: Spark Plug heat ranges

Good info, Fred. Thanks!

Tab

Re: Spark Plug heat ranges

Can anyone tell me the heat range and part numbers of Bosch plugs? I like to run the Platinum W8AP but I

Re: Spark Plug heat ranges

Reeperette /

>>What difference (if any) does it make to the oil gas ratio?

The heavier the ratio, the more heat you need to fire it completely.

>>Can you run leaner with a colder plug?

In Theory - but theory tends to fall on it's ass more often than not when dealin with mopeds...your only real resort to find this out is the ole "million monkey method" of trying a set of plugs of different ranges and doin plug chops till you get a good setup.

-Ree

Re: Spark Plug heat ranges

In that case I figure if it ain

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