Below is some data...reasons why to use a transistor ignition. It is a copy & paste article.
HOW TO BUILD TRANSISTOR IGNITION MODULES
"Most carburetor problems are electrical" That was told to me by a savvy old auto mechanic long ago and it has proven true more times than I can remember.
The standard Kettering points/condenser ignition timing setup works just fine if the point faces are parallel and clean, are closed with proper pressure, and the condenser (capacitor is the current term) is good and of the correct value. A lot of ifs, don't you think? Also, unfortunately for us model engine builders, either a grossly oversize points/condenser set from older style lawn mower engines must be used or a miniature points set will have to be fabricated from questionable materials and with questionable accuracy. Most model engines don't have shaft oil seals and just a little oil leakage onto the points will cause major problems. Ever wonder why so many model gas engines on display at shows are never ran? Do you suppose it's because they are easy starters and good runners? Some may be. But how many really otherwise great engines won't run or are so hard to start because of ignition problems, that the owner won't even bother? What a shame! If you don't like having your engines ending up as just shelf models, then keep reading!
I came across the answer some years ago in a magazine article written by Floyd Carter and all my spark plug ignition model gas engines use it with great results. The original Transistor Ignition Module (TIM - 4) is a simple two transistor circuit that can easily be home built. TIM-4 was designed to operate on 3.6 volts (three Ni-Cad cells in series) for use with model airplane engines. It eliminates all the problems of standard points systems. The coil will give a good hot spark every time. The circuit requires very little current to trigger (25 ma). This allows use of a tiny micro switch for the points which can be easily hidden. There is no arcing, so the contacts in the micro switch will never burn. If you want your model antique engine to be authentic, or on already built engines which you don't want to change, the old point set can be used if desired. A "condenser" is not needed but can be included for looks.
And now for the really BIG advantage........ Since we now have a circuit that is so easy to trigger, we can use a tiny magnetic sensor instead of mechanical point contacts (high amperage switch)! The magnetic sensor is called a "Hall Effect Device". They are really tiny, measuring just .125" x .170" x .060" thick (3mm x 4.3mm x 1.52mm). Instead of a cam to operate contacts, a tiny magnet (only 1/8" diameter by 1/16" thick - or smaller) mounted on a drum or disk (cam gear) triggers the Hall device which is mounted in close proximity. The Hall sensor is located remote from the circuit board which can be hidden under the engine, or wherever you wish. Now you have the ultimate in small and reliable ignition, no mechanical parts, rub blocks or contact points at all! The circuits are extremely reliable.
