2Smokin', I had the same bike-suddenly-die experience too and at first I thought I was getting carb freezing as suggested above, turned out to not be the case for me.
The billet smart carb has tip over valves (brass nipples seated in the fuel bowl, see photos) that have balls in the cylinder part of the nipple. The stock smart carb for summer use comes with a steel ball and a plastic ball in each nipple. When the bike tips over the steel ball closer to the fuel bowl pushes the plastic ball toward the fuel hose and seals off fuel flow preventing a tip over leak.
If you are running carb heat for winter use, the added heat eventually causes the fuel to boil and the gasses push the balls up and seal the nipple stopping fuel flow and cutting out the motor even with the bike upright. Even without carb heat I suspect this may happen if the motor heats the carb enough to cause fuel vapour to lift the plastic balls. After shutting down, as the carb cools the pressure subsides, the balls fall down and fuel will flow again.
Solution is two fold: 1. Put a valve in the carb heat line so you can regulate heat to the carb and 2. Call Corey at Technology Elevated and he’ll send you tip over valves that only have the steel balls which are heavier and don’t get pushed up to seal fuel flow as easily.
You might already have the valves with steel balls only (call TE and they might be able to tell you from your carb SN) in which case turn off all carb heat and don’t use a carb jacket. You can also pull the carb and shine a light down into the valve...the plastic balls are red and can be seen when you tip the carb over and they move closer to the nipple end of the valve.
I’ve learned that I only need carb heat when the weather is cold and that, even with steel balls only in the tip over valves, added carb heat will cause them to be pushed up and seal. I use a neoprene carb jacket as well which likely makes it so I need less carb heat than I would without the jacket.
Removal of the valves is pretty easy, use a #10 or #12 (can’t remember which) one inch wood screw, wrap it in Teflon seal tape and screw it into the fuel hose end of the valve nipple until the valve just starts to turn. Then gently clamp the carb in a vice with soft jaws or wood blocks, clamp a vice grip onto the end of the screw and use a hammer to gently tap up and out on the vice grip to remove the valve that is press seated into the body of the carb. To install the new valve add a bead of red locktite to the valve sleeve, place a long socket over the nipple and tap into place.
While you’re at it, also order from TE a stiffer throttle return spring which makes it less likely the throttle slide in the carb will stick from freezing water vapour.
The steel ball valves and stiffer slide return spring have completely solved the same issues you’re having for me and the carb now runs flawlessly right from cold start up to operating temperature and at all elevations I’ve been at...it’s a beast. Pack extra fuel and hang on!
