Steve........quote...(because it was cheap)same deal here! I picked up a DR500 in a hustle,sorry,legitimate transaction,for a pile of bike bits. My mate wanted to race a four stroke/all powers/500 class this year and as I already had my PE/DR400 I siad I would build him a bike to race.At this point I'm concentrating on getting the frame set up properly,reducing weightwhere I can,down pipe,DR or TT600 carb and just basic stuff to start,just to see how it runs .I don't mind sharing,so any mods I do that I think are worthwhile ,I'll pass on.
The last bike I built for my mate was made out of whatever we could find in the shed.........'74 DT250,plastic sheeting,old guards,a quick port job ,bigger carb ,air pod and an old down pipe/chamber from some kwaka two stroke road bike that I cut open removed the baffles and made fit.The pipe in the photos is actually an SC500 pipe that another mate of mine made but was too peaky for the 500 so I modified it to fit the 250 (at 10pm at night before the finals of the Coffs dirt track the next day)and it works like a charm.
Roger