As far as I know from reading posts and forums on this subject, it's not only the small magnet or the magnetic field these sensors respond to, it's the mass of metal it senses, which is really the same thing I guess. There is a great amount of discussion about the use of magnets per se and if they actually do anything at all.
Read this article about some tips to trigger the sensors--
http://m.wikihow.com/Trigger-Green-Traffic-Lights
.
Here is an article written for bicyclists but it applies to motorcycles too.
http://www.humantransport.org/bicycledr ... ection.htm
Attached is a technical article about inductive loops and a diagram of them and how they work.
If you do get a really strong magnet, like with 50lbs of force, be wary of picking up something on the road which can get into your chain or wheel.
If the sensor in our area is pressure activated, responds to weight, you may be screwed.
The surest way to change the light, if safety permits, is to get off the bike and hit the button at the crosswalk.
