I have multiple K, KH model motorcycles. You can bolt the magneto solid in the Advanced position - and it will start fine.
I even have my magneto timing advanced a bit further than stock(45+ degrees) for performance - and they still start fine. A "kickback" on a K model isn't as devastating to you as a kickback from a Sportster anyway. When installing your magneto, keep experimenting with your small lobe(front cylinder) so you install your magneto
without the body hanging way out (in the way of your leg). You should be able to install it with the mag head inward toward the rear cylinder. Sometimes you must lengthen the slots in the advance plate to get the exact position you need. I slide a small o-ring up the magneto shaft - to kinda pinch in there with the seal to help prevent leaks. Have the O-ring just above the surface of the magneto flat mount plate. I use short 1/4" USS coarse bolts(they start easier) and nylon insert locknuts on the bottom side. Make sure you put the LEFT SIDE(rear ward) bolt in there when installing your magneto. PS. This is great advice !
-Respectfully, Noot
The best way I set my timing on a K Model with magneto: Bump your motor over watching Front Intake Tappet go up....then it's coming down...Front piston should be coming up...look for timing mark just entering back-side of timing hole - Stop. In this position your points should be breaking on the front (Small) lobe of your magneto. In the correct position, your magneto should be all the way in (up against your rear cylinder fins) and as you slowly rotate it counter-clockwise outward - your points will just break - then Tighten it down - Perfect. If you want...you can test it by rolling your engine over a couple times - watch the intake go up, now it's coming down - front piston coming up - have your (I use foil from Pop Tart wrappers or something .001 or less thickness) between your points - and when the foil just pulls out - the points broke - look in the timing hole - and your mark should be in the hole again...
Damn I'm good !