Nope, it should fire BTDC at 28 degrees. I time mine by starting with the cylinder in a verticle position held in a vise. Roll the engine CCW and the box should fire on the way back up. On a straight plug engine Rcpilot is dead on. However if you have an angled plug it is tougher. The 28 degrees is not all that critical. At TDC the piston will toggle back and forth a few degrees. Ideal situation would be to find the sweet spot of the toggle. Point being I have run them from 22 to over 30 degrees BTDC and there is little difference. Best way is to use a degree wheel. You can print one off from CH Ignitions' site. Mount it to a piece of lite ply and go from there. All you need to add is a pointer and a piston stop. I also have the CH handy dandy ignition tester and timing box. Isolates the need to deal with a hot plug. Again this is the most accurate way to do it. Another thought if I can remember right, take 3.14159265 which is PI and divide it by 360. Multiply that by 28 and you get .2443. That is how far your engine must be before TDC in inches to fire at 28. About a 1/4 inch BTDC. Put a mark on the hub at TDC and across from that on the case. Make another at 28 BTDC. Lay a tape on that and you should be the 1/4 inch or so. This is getting to sound hard but there are many ways to do it or check it.