Cold. Though some owners said they did it hot, and said it worked too. The point being, on the Enfield, once you got the feel of the proper valve adjustment, it was something you would remember. I bet that would work just fine on these bikes too. I tried to get across to the Heist owner, that, if he goes to TDC, then checks both valves for looseness and finds one tight. DON't adjust it. Rotate the engine once around, and recheck for looseness. He would have then found that, after rotating once, he was now at TDC on the firing stroke, the correct position to make the valve adjustments. There are two top dead center's. But only one TDC with both valves closed (the firing stroke). He didn't do any harm, because he didn't try to start it. He would have spit a pushrod out and possibly caused damage, if it would have even started. With as much excessive valve clearance as he had, the valve may not even come open.