IMHO, the engine doesn't know/care which way it's mounted, even if it's on it's side. It's a matter of preference and what works best for your install. The only thing you MIGHT want to keep in mind when mounting inverted is spark plug and plug boot vulnerability. That boot will not tolerate much in the way of a bad bounce resulting in it eating dirt. An experience like that can leave it leaking spark internally, leaving you on the sidelines trying to figure out why it won't start. Not too big a deal once you figure that out. Replacement boots aren't expensive or terribly hard to replace. To that end, many veterans keep an extra ign. module in stock... -Al