I red already some old 3D on similar subjects. We all know about tearing down top-end for valve reshim: Align marks on crank (clutch side), align marks on camshaft gear, piston on TDC. Now the manual at valve check page tells about searching for TDC compression stroke. Same manual, further pages ahead, in topend tear down section, tells about searching for TDC on exhaust stroke. Why? We know that TDC on compression is with the cam lobes looking backward while TDC on ex. is 180 degrees opposite. Now, looking at how the CDI module, flywheel and pickup coil are designed the spark is signaled and fired every crankshaft rotation. So there is always a useless spark (the one with piston at TDC on exhaust). The question is: having all the marks aligned, it shouldn't matter if I mount the camshaft as dismounted or rotated by 180 degrees (very easy to happen on CRF). If it was dismounted at TDC compression, rotating the camshaft by 180, convert the "mechanic" phase to be a TDC on exhaust. The bike should fire up when kicked right as everything is aligned from a mechanical perspective and CDI send spark at every rotation. Right or wrong? Possible reasons the engine shouldn't fire with camshaft rotated by 180? I cannot think about any? Than, if above true, why the manual is so complex making all those differences? They should have told: align all the marks as indicated no matter either how the camshaft lobes are positioned or if piston is TDC compression or exhaust (TDC is enough). Am I missing something?