I found a bigger crack in the vacuum plug so figured I'd better replace it, maybe that was the trouble with starting. It was only 1 year old but was a made-in-Taiwan, cheap ass part. I couldn't locate a vacuum plug in-stock locally so I made my own from a piece of the vacuum line plugged with a piece of tight-fitting dowel and a couple clamps. It worked perfectly so I'll pretty it up in version 1.2
While I was at it I replaced the gas and vacuum lines with proper gas line tubing from an autoparts store and a new gasline filter.
I checked the spark and it seemed weak so I replaced the plugs.
I don't have a separate tank for syncing yet so I rigged up my gas tank to serve the purpose. I left the petcock on Prime to bypass the vacuum requirement.
After syncing by eye to start with and lowering the idle, it was fairing straight forward to balance the carbs. I found my throttle cable was loose too so syncing was a combination of adjusting the sync screw, the idle screw and the throttle cable length adjuster at the handlebar.
In the end it was running perfectly so I had to hop on and go for a spin. I ended up at my buddies place, who was just re-installing his back wheel. He hadn't been for a ride yet either, so we went for our first blast. His son jumped on the back of his bike and snapped a photo as we were riding.