So they don't have to hear the valve clatter!!!!! Took mine ('80) out for a short test ride yesterday, after having made a new tail light mount and getting carbs refurb'ed. Ran pretty nice, really! Clutch works great. Brakes, not so good - they are spongy, so I will re-re-re-bleed them yet again. I just went up and down a few streets in my neighborhood and went without a helmet, and dang, the valves are more audible to me than the exhaust! I'm running long drags with baffles in them. They're still pretty loud, but being so far back from where my ears are, I just don't "hear" the exhaust much while riding, unless I rev it real high. Thinking that short pipes, that end just past footpegs might supply a bit of cover-up for the clatter of the valves (which are set correctly). This isn't the first bike I've had the issue with, either. On my Sportster, I was happy to get some slightly louder slip-on mufflers, which masked the valve train mechanical noise. And on an earlier Sporty I had, I removed the windshield, because it just reflected all the valve noise back into my ears. Now I know on a normal ride (where I'd be wearing a helmet for sure) it wouldn't seem that loud. But this just sounded like nuts and bolts rattling in a can, (rhythmically, of course). Going to try the cam chain tension adjustment again, see if I can get it a bit more quiet. Funny, I don't remember my old '79 (which was my main rider for awhile) having that noisy of valves.