Quoted from orlandu81:
Thank you! I sure hope its not a gateway drug...I am maxed out in terms of space with 11 cabinets and 1 pin. No basements in Southern California
By the way, welcome to Pinside.
I recognize your avatar and user name from over on KLOV.
I know you know your way around arcade games which is a pretty good background to have moving into this.
Pinball machines for the most part are not as intimidating as they look as far as working on them goes.
Like Rarehero said, do not use lubrication for the pop bumper.
The first thing I would do is take the glass off and lift the play field up to check out the coils for the pop bumpers.
It could be a variety of simple things that fixes this.
Before you even get started taking anything apart check to see if anything is loose (nuts, bolts, brackets etc).
A lot of nuts and bolts have a tendency to come loose over time and it's good to tighten all that stuff back up.
I periodically check the underside of my machines for parts that have come loose.
After that I would check the solenoid(coil) and see if the plunger moves freely by hand or if it has a little drag compared to the other pop bumper coil.
It could probably use being taken apart and cleaned anyway, so you may want to go ahead and do that.
Things to look for would be the plastic coil sleeve on the inside of the coil (for warping) and the end of the plunger for mushrooming.
The coil heats up during play and if it gets too hot it can warp the coil sleeve and create drag on the plunger.
The plunger itself can also create drag as it wears out. Over time when the plunger hits the coil stop enough time, the end of the plunger can mushroom out and cause drag.
If its mushroomed out you can either grind the edges at an angle to get rid of the the mushrooming, or just buy a rebuild kit.
These things as well as a good cleaning should probably fix your problem.
You might also check the wires soldered to the coil and see if they are loose, cold solder etc.
I've never owned a Super Mario Brothers, so I'm not all that familiar with the ball through, ball eject mechanism or shooter mechanism.
When I have had this problem in the past with other machines it was one of the following.
1) Bad switch or loose switch in the ball through.
2) Shooter mechanisms was slightly loose and not hitting the ball dead on. I.E. one ball would make it up the shooter lane ok, but when two backed up in there it didn't have enough power to make it up the shooter lane because it was hitting the ball at a slight angle rather than dead on.
3) Low power to the machine. If you have too much stuff running on the same circuit, things like flippers, auto plunger etc are weak. I had this issue when I had too many machines running on one circuit and balls would back up in the shooter lane of my Guns N Roses.
4) You might also check the coil for the shooter mechanism. Same rules apply as above for the pop bumper as far as cleaning, rebuilding etc.
I'm sure some others guys will chime in that own this machines with suggestions.
This place is great as far as people offering help (a lot of wisdom on here).
Good luck, and congrats on the new pin.