Danger,
I did the conversion in 2004 while California was still allowing conversions. I used a BD kit and a small Electrex coil that won't provide enough power to do much. But I've only gone about 10 miles at a stretch on pavement (between fire roads/trails) and KX500freak is right. You can't really cruise at a steady 70mph. My forearm cramped up from the vibes.
Speaking of vibes, in spite of balancing the crank, I wore out the BD headlight kit. The metal back bracket fatigued into two pcs, the horn worked for about 1/2 a ride, the flasher relay became a bottle of loose rattling parts, etc. Mirrors are useless except for passing any detailed inspection. Heck, even my rear license plate vibrated in half!
I have an 18" excel laced to a new hub with some Duro DS tires and tried them once, before putting them up on the shelf and just sticking with my knobby.
Good call on the wheel balancing, though. I have ALL my wheels dynamically balanced and dont' really want to add an extra rim lock, so it makes for a lot of spoke/stick-on weights. The balancing is a noticible difference, expecially at speed.
I enjoy riding this bike on all kinds of trails and fire roads along with my son's plated KDX. I carry a liter of Yamalube 2R and a turkey baster for precision oil measurement. It looks hokey, but works well. I have a small dual chamber oil mixing bottle for Sears weed trimmer that I would like to try sometime. You squeeze the oil into the upper chamber to the appropriate measurement, then pour from that chamber in your tank. Simple and compact. Hope it seals OK after I fill it with Yamalube.
I only get about 40 - 50 miles per tank, and I have an additional desert tank that I have not tried yet. After 1 tank, I'm ready for a break!
Barry