the "screen" is not a spark arrestor, it's a catelitic converter of sorts and they put it in the exhaust to meet epa standards.
really, it's nothing more than a blockage in the exhaust that will trap unburned oil and get clogged up.
so you're saying that removing this is illegal?
then how come it is legal for places to sell expansion chambers and other exhausts for these engines that do not have the "screens" in them? I bought a long pipe (poo-poo) that has a muffler on it with nothing in it but a baffle.
NONE of the expansion chambers or high performance exhausts have this "screen" in them.
there's a big difference between a cateletic converter and a spark arrestor.
this "screen" actually doesn't act like a cateletic converter at all. all it does is trap unburned oil to minimize it from getting spewed into the air.
this is how they can "meet" epa standards.
here's what the "screen" looks like.
if you ever notice, chamsaws and weedeaters do have spark arrestor screens in the exhaust. BUT, if you look close, the exhaust is nothing more than a little box that is VERY close to the exhaust port. sparks will come out of an exhaust that is that short, so that's why they have spark arrestors.
some 2 stroke dirt bikes did come with spark arrestors, but most just had an expansion chamber and a baffle.
