Looking to upgrade the plugs in my 09 Arctic Cat Thundercat
Any opinions as to what would be a good choice?!

 

Is there a problem with the stock NGK CPR8E that it came with?
Has the machine been modified?

 

All ready replaced them once (200km) before I modded my bike because they were all fouled up.....
I have an HMF Swamp XL Series and UNI air filter now

 

Very soon a Dalton clutch kit and Power Commander V

 

bump

 

I really wouldn't consider a plug change an upgrade. Some plugs manuf. are better than others but the main thing is the heat range. If you are increasing fuel and timing, and you are driving it hard, you might consider a range colder. An upgrade would be a more powerful coil so you could open up the plug gap some.