i finally got my trail duster to run the other day,and we had it running for a bit while tuning the idle screw on the carb and i shut the motor off and tried to start it back up and it would hardly crank. the alternator i had on there was one i got from a 79 w200 and i compared it with the one that was on there originally,and from the front they both look the same and the electrical connections are the same,but the backside of the alt. look totally different. so i put the original alt back on and now when you start it up the pulley doesnt turn but when you take the belt off and spin it with your hand it spins freely. am i putting the belt on too tight? or is my alternator screwed? also can anyone explain the differences in the alternators? i'll try to get a picture of them side by side to give an idea of what i'm talking about.