Registered Forum User
500SD
Bikes: Diavel
Posts: 746
Join Date: Mar 2002
Location: Mansfield, Notts
I'm sure you've checked this stuff but just in case:
My old 851 backfired on the overrun when I first got it, it turned it had standard cans with an upgraded chip and SP airbox upgrade, so it was getting it in, but couldn't get it out quick enough ! Pair of termi's sorted it and improved the power.