I HAVE A 25 MODEL T WHICH STARTS AND RUNS PERFECT ON THE BATTERY AND IT RUNS PERFECT WHEN I SWITCH IT OVER TO THE MAG. HOWEVER IT WILL NOT START ON THE MAGS. IS THIS NORMAL.
Unfortunately, yes. It should start on MAG, but they often don't because of weak magnets and/or excessive gap.
The spark lever should be down a few notches for starting on MAG. If you've been trying it with the lever all the way up, try this. If you're lucky it will be all you need. More likely the magneto needs fixing.
Depending on the problem, you might also try to recharge your magnets while they are still in the car.
Here are a few past thread on the subject.
You can also look on Youtube for videos of how its done.
Hope this helps
Wayne, I had the exact same situation for a while and the immediate solution was as Steve said. Advancing the spark is essential. Make sure your mixture is set rich enough for starting and a bit of priming on the first turn might help too. I tuned my coils with a Strobospark tester and installed new Champion X plugs and that has helped too. When warm, my car is a crack start on battery but still takes 3 to 6 revolutions to start on mag. This is using the starter. Using the hand crank, it will start on one hard swing of the crank on mag every time. Never understood that one. Let us know how it goes.
Here's a tip. Get your engine to a slow idle on mag. As you push up on the spark lever note the position where it will idle smoothly and then if you push it up further, it will get rough of die. The most retarded position where it will idle smoothly is the position it will start on mag. The first time you try, be sure to pull up on the crank with the left hand and let go of the crank as you pull upward, just in case it kicks. If it doesn't kick, that is the place to put the spark lever for mag starting.
I would be careful watching videos of magneto recharging on Youtube. Not all of them show you the entire process of how it's done, or even how it's done in the manuals.
Other then having the correct timing for mag starting the other requirement that is different then battery starting is the required cranking speed. You have to crank it fast enough for the mag to generate the power.
On my T it has to be cranked at 115 rpm or faster to start on mag power.