Jim magnets cannot be what they used to be... can remember the timing slipping on the ES2 and a serious overheat.. the pipe glowed cherry red almost to the silencer.. but the mag kept working and it itis of course under the dyno and closer to the cylinder so less air circulating . Years later it has begun to show classic signs of impending failure... erratic cold starting and no hot starting. Will post what the reconditioners find usually though this is a sign of condensor failure. But thanks for posting the barrel temps , much higher than i would have expected -the next time mine is off will investigate enlarging the casting holes between the cylinders.
Copied from coolmagnetman.com
Concerning NdFeb "rare earth magnets" The most powerful magnets around. Used in some newer magnetos because they make a big hot spark at low speed.
There are definitely other types of magnets available that easily handle the temps but they are not nearly as powerful.
"Neodymium-Iron-Boron Magnets
NdFeB magnets are the strongest permanent magnets around today, and are not very expensive. They are used in headphones, disk drives, new toys, all over the place.
a. Mechanical Shock
These magnets are brittle - they will chip or crack or break easily when:
dropped onto a hard surface
allowed to smash together with another magnet
allowed to smash together with a piece of metal
struck with a hammer or other hard substance
So again, handle gently, like you do with your iPod or cell phone. When you bring two magnets together, be prepared to have the force of attraction increase quickly and dramatically as the North pole of one gets closer to the South pole of the other. Better still, place a plastic disk or rubber washer between them so there is a cushion between them. Watch your fingers so they don't get pinched! Because these magnets are so much stronger than others, this needs to be a real precaution!
You may not realize it, but every particle within a magnet wants to push away from every other particle next to it. Yes, it is attracted to the particle at its North end and South end, but all along its sides, there is a repulsion. Because of this, if two magnets are allowed to smash together, expect a small chip or particle to fly away at a high velocity and can fly into your eye. That is why it's a good thing to wear goggles - protect your eyes from the unexpected. Those particles have sharp edges and will easily scratch your eyes.
b. Heat
This is the weakness of this magnet.
Their maximum working temperature is only 150 degrees C (302 degrees F).
The Curie Temperature for NdFeB magnets is 310C (590F).
This is why they usually aren't used in motors. Keep your magnets cool. "
