I'm running a 2002 Xc 700 sp
it has 500 main jets my plugs are dark brown and a tad oily when I remove them
just bought 490 jets
by going down 1 size am I in danger of "holeing" my pistons?
I don't think so but any input would be helpful http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/biggrin.gif

I wouldnt think so http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/biggrin.gif

Man, I can't remember the specifics, but I know that in one of the last couple Snow Techs, they had an article about the Mikuni jet sizes right around the 500 mark being a little off. *Meaning you think that one size is too lean, so you go up one which is actually leaner (could be real trouble). *I think it might be the 490 to 500 jump meaning the 490 is actually a little richer than 500. *Anyone else remember the specifics? *I'll take a look to see if I can find that article again.

Either way, watch the plugs and ideally get bend-a-light and look for piston wash.

Actually I just read the article 2 days ago. *It was the 520 jet that was actually leaner than the 510. *It has to do with the numbering system used by Mikuni that the smaller size jets overlap the larger sizes (for some reason) in the flow rate. *The specs for a 700 XC VES went from a 510 to a 530 for colder temps for that reason.