Gx390/Gx 440 Spark Plug

[rustedandweathered]

Am running the Gx 440 on 1/4 mile...Stock...Gas...What is the best spark plug for it ?

 

[level600a]

Stock.

 

[Aaron_Pollock]

I don't know if it's the best, but I run the 3910X in mine with no issues.

 

[Kart43]

Use the NGK plug you won't find one better, the Autolite AR do work well and fill the chamber a small amount.

 

[alvin l nunley]

Because the plug you have now is probably right for an industrial installation, where the engine runs at a fixed RPM, I'm thinking you need a colder plug for racing. I'm sure if you could find a listing of heat ranges for that plug, there will be a hottest and coldest, try the coldest. The colder plug may require some fuel mixture tuning, be aware of that.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley) what

 

[rkcarguy]

I am using a BPR7ES in my 420cc predator and have changed the cap to a non-resistor cap.