Quoted from Who-Dey:
Mine started doing the same thing and the opto sensor was off that issues in front of Sparky. I ended up having to bend the metal tab a little that holds the opto sensor. The bad thing about it is, that its hard to see and get to because of the left ramp and other things being in the way. I ended up taking the left ramp off of the game and the plastics around Sparky so i could see what i needed to do better. It actually wasnt that big of a job but after about three failed attempts of trying to get it adjusted I said F it and took the ramp off so i could have some room to work and so that i could see what to do.
I was getting sparky hits just by flipping the flippers and yes it does ruin the gameplay for sure. Maybe someone else can Tell you a better way to fix this problem but thats how i fixed mine. If you look in front of Sparky you will see where the opto sensor shines from one side to the other. There will be a round red circle of light that is supposed to shine into the hole on the opposite side of the opto and mine was way off and barely shining into that hole. I suspect that this may be your problem also. Its also possible that the switch that sits between Sparkys legs may be too close together and registering way to easy. If thats the case you will need to gap that switch open a little more. Check that switch first and then the opto. If the opto is off center though i would say that is your problem. Good luck!
Well i need to edit this comment a little lol. My MET started the false Sparky hits again so i tore into the game one more time. I earlier stated that you need to take the left ramp off to bend the bracket a little so you can get the opto aligned better. You can see the opto light move when you lightly move the rail so you will know which way that you need to bend the rail a little. You probably can just take the plastics off around sparky and take a pair of needle nose pliers and grab ahold of the rail that holds the opto and bend it a little without removing any ramps so that is nice.
Also the first thing that you can do is to unplug the opto connectors under the playfield and plug them back in to make sure that they are making a good connection. The little opto plugs are typically kind of loose and can come unplugged or become loose easily.
Im not a expert pinball repair guy so i kinda learn as i go and get a little better the more i work on these games. At any rate i was just trying to help Creepy Tom with the opto problem and now i kinda feel bad because tonight i found an easier way so im hoping that he reads this before working on his game. This game has been a huge PIA so far compared to my other new Sterns.