ORIGINAL: speedracerntrixie
Matt, I was just looking at where the crankcase pulse comes from for the carb. Appears to be the back plate. Maybe after the ring seats it will give a better pulse and the carb will prime better. I wonder if anything can be done to increase the pulse?
Speedracer,
I changed the tube early on. They had a length of 3/32" yellow gas line as the pressure pulse line. As I was investigating, I saw that the tube was slightly pinched against a corner and had a definitely dimple. I changed to a length of 1/8" neoprene from McMasterCarr and moved the nipple a bit to eliminate the pinch point.
The 1/8" line doesn't change the pressure pulse to the carb. Pressure is unchanged (whatever the crankcase pressure is) but the larger hole in the tube allows a little more volume due to the increased cross section. But since it a static situation and the runner length is short (1"), I doubt it matters much.