a mildly ported banshee, done by the right shop will be just as reliable as stock.a banshee has no more normal upkeep than your 400.check for loose nuts and bolts, grease all zerks,oil and make sure the chain has the right amount of play.keep the jetting right for your altitude and temp. make sure you have no intake air leaks and you will be golden. on a 75 hp banshee i have gone 2 years without a rebuild.beating the balls off it weekly.