Someone on the other forum mentioned that it might be that the gas cap was too tight. After letting the engine sit for two days, I checked the cap. Sure enough, it was VERY tightly screwed on, so I loosened it up and retightened it. After three pulls, the new engine started up!!

So I rode itr to work, which is five miles away. It rained enroute, and I was pleasantly surprised that the bike's rear tire slipped just once during the ride. With single engine, I'd have to feather the throttle all the way for miles. Traction with twin engines is excellent. Since the roads were wet, I wasn't able to full throttle both engines, and the new engine is still breaking in. Power and acceleration with the extra engine with 1.25" roller is excellent. I just need to keep both clutches engaged. If not the idling engine's spindle drag causes substantial resistance which the working engine has to overcome.

No problems whatsoever so far, except fore that one incident with vacuum lock in the fuel passage. Today, I'll take the long way home and challenge the hills.