SFO made a spark arrestor for the Italian made Arrow pipe on his YZF because Arrow didn't make one. It was a work of art, far better than anything I've seen from ANY manufacturer. BUT, as DRZ-Dad pointed out it wasn't Forestry department approved and they wouldn't let him ride with it, despite the fact that his was more effective than the approved versions. He finally had to sell the pipe because he couldn't use it anywhere that he liked to ride. Seems unfair but those rules seem pretty much set in stone.