My old mans got a 1998 polaris xc 700 and he was running ngk sparkpugs in it and one day when he fired it up it started running on one cylinder. He got it to run on 2 and it went back to 1. he thought it was the cdi box. But he went and bought some eridium sparkplugs and it runs fine now, but as soon as u put the ngk's back in, it goes to 1 cylinder. I think its the cdi box not giving off enough spark, but when u put the eridium sparkplugs in it, it makes up for the loss of spark the cdi gives out. What do u all think?