This arrester is welded on to the end of my 68DT1 exhaust. Why would someone add that? Anybody seen one before? Kind of a shame since the exhaust is so smooth with no rust or dents.

Original '68 exhaust pipe did not have a USFS approval stamped into it, and I believe they did not have spark arresters built in (although I might be mistaken there). Somebody likely added the aftermarket spark arrester to comply with the stamped "approved" lettering when they rode in forest lands. Obviously the collector value of unmolested '68 DT1s were nothing to speak of back when that was probably done, so it wasn't exactly a sin back then.

Thanks again …it looked interesting. I have another 68DT1 exhaust with the long end that curves slightly towards the rear wheel. I believe I’ll use that one for the resto. If this arrester installation isn’t anything desirable I may try and remove it but it is welded very thoroughly onto the end…the rest of the exhaust is just mint as hell.

It's interesting that the 68 didn't have the Krizman stamp...  Yamaha was using Krizman spark arresters on their "trail" bikes as early as 1964...  I think the early ones may have said USDA approved instead of USFS.

I wonder if the DT1 version just didn't get approval yet or if maybe Yamaha didn't want to spend the time and effort for approval on an "experimental" model or something. 

I didn't think to look at the stock exhaust for the arrester stamping...and sure enough neither of my 68 exhausts have any stamping on them like I see on my other bikes.