im trying to get my big red running perfect, but unfortunatly the local parts store only had ngk "8" plugs......there running white hot, so i dont want to run them too much. i messed with the clip on the needle, but i think i just have too low octane fuel, and too hot spark plugs. im running mobile 92 octane...do you think thats enough? or maybe will it run better by going down a heat range on the plug?---knowsalot, your an expert on tuning these things....what do you think?

 

You said NGK 7 or 8. If you go to a 7 then you will go hotter than the 8. If the plug is turning white then your lean

 

odyssey,

If this is on your 250,...Unless you use your trike for pulling things and puttin around, go with the 8 range plug.

Lower the number, hotter the plug, but not in terms of how hot the spark will be, but in terms of how fast the sparkplug will get rid of the heat. Slow speeds cause more heat, so a hotter plug is used to manage it's escape.

Low numbers[hot] for utility use and high numbers[cold] for hi performance use. Seems odd, but that's how it works.

In your situation, I know that the theory would be to change the heat range of the plug to compensate for the lean condition, but it will only make matters worse by going to a lower number sparkplug....unless you do indeed run at slow speeds.

I would go back to the jetting and work from there.

If this is on your 200, a 7 or 8 should be OK. I have only ran 7s in all my 185/200 series engines for years. I have found that the 7 does a better job on these engines due to the high tempratures these engines run regardless of how you use them.

If this is on your 250, stick with the 8.

 

knows, its on my 200, im running a 12-1 piston in it, i think thats what causin the problems. im gonn atry some octane boost tonight. i richened the carb by movin the clip lower on the needle, but the plug center looked white, while the thread part looked black. so, let me get it straight.....i thought the "7" plug dissapates more heat...has a colder tip temp?or is it the other way around?---if thats the way it works, the 8 would be better for mine than the 7 i would think. i dont really run it too hard, mostly low speeds on hills.

 

You have it right, the 7 does dissapate more heat than the 8.

A 12:1CR is ahuge jump from the stock 7.6:1CR......You have nearly doubled the ratio...LOL
Major fiddling with the jets will be a given.

 

and also race gas, more than 11:1 needs race gas