spark plug

An 8 is a bit hot for an 85, I would probably run a 9, and correct the jetting to keep from fouling plugs.

my 88 kx 125 used a 10 stock, but as well i used a 9, the 9 would be a better choice for you 85 :nod:

the difference is heat ranges, 10 be cold and 8 being hot a colder plug has a shorter insulator which dissapates heat quickly, while a hotter plug has a longer insulator and dissipates the heat more slowly. ;)