Two ideas. The first is that you're drawing too much acetylene too fast, and are
getting acetone drops in your gas stream. This is bad news. Remember, you can
only draw 1/7th the tank capacity.
The other idea is that your regulator needs servicing. If your diaphragm is
sticking, it can start bouncing like that. If your regulator is made by an
offbrand or import manufacturer, this is the first thing to suspect. Most Harbor
Freight Victor torch kit clone regulators have sticky diaphragms. They can be
repaired, need to take them to a good regulator repair guy. If your town doesn't
have one, send them here, because Seattle has a real good one:
Hansen & Miller
4101 Leary Way NW
Seattle, WA 98107
No email, no Web page, not cheap, excellent technicians, best around.