Has anyone tried a colder NGK spark plug? I read that they may be needed if you do a lot of high RPM riding. Also, I have had trouble reading the spark plug when the DS is hot. Either it is running slightly lean or the plug reading is false. If I check the plug after a real short ride through the first couple gears while the DS is still warming up, I get a much richer reading than when the DS is hot. Also, I tried those cheap & easy to get Champion 809 (RA6HC) plugs and I am suspicious that they are not the right plug for the DS. I would stick with NGK. www.ngksparkplugs.com

 

In my opinion, plug reading should take place after the machine has warmed up, and under normal riding conditions.

In regards to a cooler plug, that's not a bad idea, especially (like you said) if your burning 6000+ rpm's constantly (in the sand or whatever).

 

In stock form I can't stand the bogging at less than 3500 RPM, so I always try to keep the RPMs up (I run a 38 tooth rear sprocket). I ride in Texas with 100+ degree temperatures. I installed colder D9EA plugs even though the stock DR8EA are a cool plug, and the DS is running a little better. I do still have a lean condition though with a K&N filter.