I have a 1979 Clark forklift C300 /40 serial #356-37-4370 with a Continental F163 engine, running on LP. The engine starts and idles. It also runs at very high rpm. However, when accelerating from idle it is very rough running or when putting a load on it. Driving along at mid rpm it runs very rough, sounds like it is chugging along. Plugs, points and settings seem ok. Can this be the LP regulator? Any cleaning of this needed?

Thanks in advance,
Rick