Why is it that S&S can build and sell big bore air cooled V-twin motorcycle engines without having to worry about complying with EPA smog rules, but Harley Davidson does.

 

I think it may be because S&S isn't regulated as factory original equipment is like Harley-Davidson. Aftermarket has a different set of regulations. I'm sure EPA will get around to the aftermarket soon enough.

 

They do make a epa compliant motor, called the wedge or something like that, even legal in USSR (Kali).

 

Because you are buying the S&S motor for "off road competition use" or some similar verbiage.

It's not for getting a factory produced bike thru EPA regs onto the street.

Eventually IMHO, testing is coming to squash the common epa mods/noncompliance issues.