Basically I undo the cap, prime the black bulb till pressure is there then I pump the lever under the carb. Screw the fuel cap down and it starts second pull. It runs with no issues. I trimmed my hedges today and it ran perfectly.
As for tampered with, I think it's all original. The pictures of the HT-20 in my first post are from a unit for sale on Gumtree. It looks identical to mine with both a primer on the black fuel line and a lever under the carb. This also matches the diagram I pulled off the net.
A manual would be great but I cannot find one on the net.
Inside the carby air filter housing is that typical looking date code stamped on plastic parts of power equipment I have played with. Mine says 8th '93 so if that is to be believed, it is an old unit in good shape. Finding a manual or even just reference to the correct starting sequence would be difficult.
