Transistor question

Some friends and I from a Suzuki motorcycle forum are having some trouble locating a transistor. It belongs to a cdi ignition module on our early 's motorcycles. After some trial and error we determined that the transistors were bad. We have found a replacement (radio shack #276-2020 tip3055 npn type) but it seems it gets too hot under normal use. Can anybody help us figure out an alternative component so we dont get stranded on the side of the road? Any help is greatly appreciated.

What was the original part number on the transistor? You have replaced it with a power transistor with hi wattage. It should have a heat sink - if it is still too hot with the heat sink on it chances are you have another problem. what cause the other transistor to go bad ?? Bad coil maybe? Or should I say going bad - like it may have some shorted turns which would cause the current to rise and cause the transistor to get hotter.

How hot is too hot? The transistor junction can run 125 deg C and be reliable. As a quick but effective test see if you can keep your finger on it during operation. If so this indicates the transistor case is 70 deg C or below. This would be fine. If it sizzles a wet finger it is too hot.

It is normal for some transistors in some circuits to get very hot, due to the current passing through them.
Therefore larger (high power) transistors are commonly mounted on a heat sink to prevent them getting too hot.
The TIP3055 datasheet says it is rated at 90 Watts so yes, even if that is sufficiently similar to the original transistor, it may well get hot !
Is there someome on your forum who has one of these ignition systems (without a fault) who can tell you if the original part normally gets hot ?

So if the original transistor was bolted to a lump of metal, make sure your replacement is bolted down to it before you turn the ignition on.

Can you post a circuit diagram and maybe a picture so that we have some more information to figure out what the problem might be ?
And as David says, what is the marking on the original transistor, and could it be that another component in the circuit has caused the transistor to become faulty ?

Not sure of the original part number. It does have a heat sink but compared to a good unit, it is much hotter. Bad coils are probably what killed the original ones, but they have been replaced with new ones of similar resistance.

MEASURE THE CURRENT OF A GOOD UNIT AND THEN COMPARE TO THE CURRENT YOUR UNIT DRAWS. I AM OF THE MIND SET THAT YOU HAVE AN ADDITIONAL PROBLEM, CAUSING YOUR UNIT TO RUN HOT - LIKE MAYBE A GROUND

what model suzuki ? if it is a true CDI, and they are the switching of the "CD" part of the circuit , they are switching in excess of 300v.
this is usually on old 2 strokes. if its a 4 stroke, then its a different story. also check you have the coil polarity correct,

As well a bolting the transistor down, did you use thermal paste (also called thermal grease, thermal compound, or thermal gel)? That can make a huge difference, as the paste provides a conductive path for the heat from the transistor case to the heat sink.

Its a 1983 gs550e. 4 cycle, 4 cylinder.

The CDI circuits I've seen use a high voltage transistor to drive the ignition transformer primary.

Is the transistor in question used to switch the transformer primary or is it the inverter transistor to generate the high voltage?

*transistor * **is a simeconductor device use to amplyfy and switch electronic signals and electronic power