# Stern Tech School: Flipper Maintenance

**Source:** Stern Pinball  
**Type:** video  
**Published:** 2025-03-26  
**Duration:** 17m 47s  
**Beat:** Pinball

**URL:** https://www.youtube.com/watch?v=NVY2PcXJ2eU

---

## Analysis

Stern Pinball's Kyle provides a comprehensive technical guide on flipper maintenance and rebuilding, covering wear diagnosis, component replacement, assembly procedures, and critical adjustments like end play and alignment. The video emphasizes that flippers are wear items requiring periodic maintenance, with the crank and link being the primary components that deteriorate and affect gameplay performance.

### Key Claims

- [HIGH] During a standard 3-minute 3-ball game, players actuate each flipper hundreds of times, making them wear items that affect gameplay — _Kyle (Stern Pinball), opening statement on flipper wear_
- [HIGH] The crank and link is the primary component that wears out on a flipper assembly, causing loss of strength and crispness — _Kyle identifies this as the main wear component during technical explanation_
- [HIGH] When replacing crank and link, the coil stop must also be replaced because these parts mate together and wear as a pair — _Kyle emphasizes this replacement requirement and demonstrates wear patterns_
- [HIGH] Proper flipper end play should be approximately 1/16th inch or about one millimeter (roughly two credit card widths) — _Kyle specifies measurement during assembly and testing phase_
- [HIGH] Newer Stern games use Allen head cap screws (5/32 inch) for coil stop attachment, while older games used 5/16 head screws requiring a different tool — _Kyle distinguishes between coil stop screw types and required tools_
- [HIGH] The coil sleeve should be replaced during flipper rebuild because a worn plunger can mushroom and create friction inside the sleeve — _Kyle demonstrates wear deformation and explains friction problems_
- [HIGH] Stern Pinball is producing educational tech school content demonstrating ongoing commitment to operator and owner education — _This video is part of an established educational series (referenced as 'another Stern Tech School video')_

### Notable Quotes

> "With the flippers being the primary way you interact with a pinball game, a like standard 3 minute three ball game of pinball you could actuate each flipper you know hundreds of times and they are wear items."
> — **Kyle (Stern Pinball)**, Opening
> _Establishes the fundamental concept that flippers are consumable components requiring maintenance_

> "The primary way most people will notice a flipper is starting to wear is it will not feel nearly as strong or crisp as a new game when you first purchase the game."
> — **Kyle**, Wear diagnosis section
> _Provides practical guidance for players to identify flipper degradation_

> "When this plunger starts moving into the solenoid, it having to take up that slack, that slop there, that directly relates to a lot less force imparted on the ball."
> — **Kyle**, Mechanical explanation
> _Explains the mechanical relationship between wear and gameplay impact_

> "To rebuild your flippers you really only need one tool: a 5/32 inch Allen wrench."
> — **Kyle**, Tools section
> _Emphasizes accessibility of flipper maintenance for home owners and operators_

> "We need to have about a 1/16th of an inch, maybe you know, a millimeter or so—a teeny amount of up and down play—so the flipper pawl, the square section here, the crank, does not bind up against the flipper bushing."
> — **Kyle**, Critical adjustment section
> _Specifies the precise end play measurement critical for proper flipper function_

> "I can see this is moving a bit. I can also hear a slight clunking, just a little bit when I move it up and down. That's how I know that I have just enough end play in this flipper."
> — **Kyle**, Testing phase
> _Provides tactile/auditory feedback for verifying correct end play adjustment_

### Entities

| Name | Type | Context |
|------|------|---------|
| Kyle | person | Stern Pinball technician/educator who presents the flipper maintenance video |
| Stern Pinball | company | Manufacturer of modern pinball machines; producer of Tech School educational content |
| Stern Tech School | event | Educational video series covering pinball maintenance and technical procedures |

### Topics

- **Primary:** Flipper maintenance and repair, Wear diagnosis and symptom recognition, Component replacement procedures, Critical adjustment techniques (end play, alignment)
- **Secondary:** Tools and equipment requirements, Operator and owner education

### Sentiment

**Positive** (0.85) — Kyle presents technical information in an encouraging, accessible manner that emphasizes flipper maintenance as achievable for home owners and operators. The educational approach and step-by-step guidance convey confidence and support for the community.

### Signals

- **[community_signal]** Stern Pinball producing educational tech school content demonstrates ongoing commitment to operator and owner education/support (confidence: high) — Entire 'Stern Tech School: Flipper Maintenance' video is part of an established educational series (referenced as 'another Stern Tech School video' at conclusion)

---

## Transcript

Hello I am Kyle with Stern Pinball and in this video we are going to go over flipper maintenance. With the flippers being the primary way you interact with a pinball game, a like standard 3 minute three ball game of pinball you could actuate each flipper you know hundreds of times and they are wear items. They do wear out and when they wear out it can and will affect gameplay right.

So the primary way most people will notice a flipper is starting to wear is it will not feel nearly as strong or crisp as a new game when you first purchase the game. Might be harder to make it up ramps. You might notice that it drags a little bit, maybe it doesn't reset as smooth as it did when it was new. The primary component that wears out on a flipper assembly is what we would call the crank and link. Here is a uh well used uh crank and link. Keep your eye here on the link and watch how much movement we get when I try to compress it and then pull it apart. There's a lot of slop there. Why does this cause problems? So the way that the flipper works, which we will see here in just a moment, the solenoid will energize and attract this plunger, which then starts a chain of movement. When this plunger starts moving into the solenoid, it having to take up that slack, that slop there, that directly relates to a lot less force imparted on the ball when you start to go, you know, try to make a ramp or something like that.

How do we fix this? We replace this unit. We can replace the entire crank and link. When you replace the crank and link, we also want to make sure we replace the coil stop. The reason why this also needs to be replaced is because they mate together. When these things slam into each other, let's take a look at the assembly and how they kind of all interact with each other.

So the entire flipper assembly is comprised of the base, the coil stop, the solenoid, the uh there's a stopping bracket here that holds the coil in place. You've got your crank and link and plunger assembly here, uh you've got an end of stroke switch here. You have a flipper bushing which is underneath the crank. Uh the flipper pawl here, uh which is kind of hidden, um but the flipper bushing is what allows the actual flipper bat above the playfield to pass through and then attach to the uh crank and link here.

How this works simply: the solenoid here energizes, creates a magnetic field, it pulls the flipper plunger here, in which then rotates the flipper bat, which is this uh circular bit here in the flipper crank or the pawl, and that rotates the flipper. I'm going to hold the top end and I'm going to wiggle the plunger a little bit. If you keep your eyes here on the link I'm on the top side rotating the flipper bat, I'm holding the plunger in place and we've got that bit of free play right there. It's a little worn but it's not too bad.

To rebuild your flippers you really only need one tool: a 5/32 inch Allen wrench. Um here are some examples: a 5/32 inch Allen driver, a 5/32 inch T-handle Allen driver. This is really useful because these are torqued rather strong, um so you might not be able to loosen them by just using a driver or what most people will have at home is an Allen key set and having a 5/32 inch Allen key like this uh will also do the trick.

The only caveat to the tools you'll need to rebuild a flipper is in the last few years we did switch to using the Allen head cap screw as shown here that uses the 5/32 inch to remove. On older production games, the coil stops were held in with a 5/16 head screw. Here's a 5/16 head with a 10/32 thread pitch. So if yours does have these silver screws that hold the coil stop in place, you will need a 5/16 inch nut driver to remove those from the flipper base plate.

All right, so to disassemble your flipper we need to remove the two screws that hold the coil stop to the assembly. If you don't have a driver or a T-handle, which makes things very easy to get in from the top and to loosen that screw and drive it out, um I can show how we can use a standard Allen key in some tight spaces. We're going to want to use the shorter side to drive the screw, uh because doing that allows us to use the torque of the longer side of the key, use leverage to loosen the uh screw here. We're going to want to remember left. We're going to turn this thing down and towards me. At this point it might be loose enough to use the long side of the Allen key to be able to spin this off quicker. Like that. So now we'll use our Allen key to remove the other screw.

Once this screw comes off the coil and coil stop will be loose and they're going to want to move down. We'll be able to move the coil upwards and we can pull our coil stop out of the way. This wave washer is able to kind of tension the free space that exists between the coil stay and the coil stop to keep the flipper coil, the solenoid itself from moving or vibrating. So make sure to keep that and uh don't lose it.

Now with the old coil stop removed and set aside, we can snake the flipper solenoid out of place. Here, almost every coil on a pinball game has a sleeve. Um this sleeve lines the inside of the bobbin. A coil is a wire that is wrapped around a bobbin, which is this frame—uh this nylon frame—and the sleeve takes up the slack on the inside.

Let's examine some things that happen as the coil actuates. The stop stops the plunger. That's what keeps the flipper movement arrested, right? And like I mentioned earlier, these wear together, so you want to make sure you replace these as a pair. What happens when you have metal slamming against metal? The tip of the plunger starts to deform. It flattens and uh starts to wear down the flipper plunger. What happens then is it starts to get a bit of an edge to it. This is another part of where we were going to start losing power in our flippers. When you get a mushroomed over top, the end of this can become wider than its prescribed diameter. And when it moves inside of the sleeve, it can create a lot of friction.

So not only do we want to make sure we replace the plunger and the stop as a pair when we rebuild our flippers, it is a good idea to replace the coil sleeve.

Now with those parts removed, we can take our Allen key again and we are going to loosen the flipper pawl or the flipper crank off of the flipper bat's shaft. But here, uh what I'm going to do is I'm going to hold the flipper in place and I am going to loosen like so. With it loose, we can start to twist and pull the flipper out through the top of the playfield. And now our pawl is loose.

With the flipper bat removed, we can now remove the crank and link. The last step we have is to remove the flipper return spring from its uh stay, which is screwed onto the crank or pawl here. This process can be a little tricky, but what we need to do is get the uh small opening on the spring off of the stay bracket. I'm going to try to push it up and bring it around. Just like that. And now with the spring removed, we can remove the plunger and link from our flipper plate.

Now that we have all of the old flipper parts off of the flipper base, uh one thing I do like to check is the flipper bushing itself. The way I like to do that is I'll grab a screwdriver, or you can use the flipper bat, and what I'll do is put the screwdriver inside the flipper bushing and start to apply a bit of pressure in a circle and take a look to see if you can see the flipper bushing cracked around its uh between its flat portion and the portion that sticks out towards you. If the flipper bushing is cracked, that will also cause a lot of um undesired play in the flipper um and can also translate to weak or bad performance.

Since this game is uh not heavily used, the flipper bushing is fine.

The first thing we're going to want to do is grab our a flipper crank and link. You will purchase them and they will be assembled with their switch actuators on on them. uh the switch actuator is in place with the spring plate. There is a left and a right. If both of these are not marked, there's one trick that I've learned to be able to tell them apart. If you notice on the switch actuator there is a rivet and kind of a hollow section—um it kind of turns into a cup. If you face this round rivet and the cup away from you on both of these, when the switch actuator is facing the right, it is the right side uh crank link. If it's on the left, it's the left side uh. We're doing the right flipper, so I'm going to use the correct side.

What we'll do is take the uh crank and we'll kind of fold it into the position that it naturally sits in and we'll lay the flipper plunger through the coil's stay here and I will stick the uh shaft of the flipper through the flipper bushing on the uh top side of the playfield and we will slide it into the hole in the flipper pawl here and this this will help just give us a place to kind of hang the flipper pawl and keep it from moving around too much um. While I'm here I'm also going to hand tighten this screw as much as I can.

Our next step is to reattach the flipper return spring. Want to catch the side of the spring that has the opening into this small hole right here. Now with the spring reattached, we're going to insert our new coil sleeve into the coil. The side of the coil with the solder lugs goes away from the coil stop. The flanged end of the coil sleeve goes at the coil stop, so we are going to insert it like so.

Kind of in one fell swoop, we're going to take the coil, slide it up over the plunger on the plunger and link, put the wave washer on to the coil stop and press it in place so the core of the coil stop is in the center of the coil and we can kind of pinch it in place here while we go for our hardware. We'll get our cap screws. Now that we've started the screw, we can drive it in with our Allen key. uh we're not going to tighten it down all the way. We're going to want to start the other screw first before we torque it in place.

Now with both of the coil stop screws snug, we're going to torque them in place. So we will position our Allen wrench in a way that allows us to tighten it. A good swing of the wrench here.

So now we have everything pinned in place. uh we are going to need to tighten the crank and link down around the shaft of the flipper bat. There's an amount of free play or end play that we need between the flipper bushing and the bottom of the flipper pawl. We need to have about a 1/16th of an inch, maybe you know, a millimeter or so—a teeny amount of up and down play—so the flipper pawl, the square section here, the crank, does not bind up against the flipper bushing.

So what I'm going to do is we're going to roughly set the flipper right now and I'm going to use my Allen key to kind of just take up some of this slack in the screw. We're going to get it snug but not tight. But once we get to a point of resistance, the flipper will move. The reason this is important is because this is where we are going to need to set the level of the flipper, the angle of the flipper on the playfield, and also adjust in the end play.

For the purpose of showing this to the camera I have put the playfield down into the forward service position. But what we need to do now is to align the flipper with its indentation on the playfield. These are used uh for you and for the factory to line up the flippers to get them hopefully set up right the first go. So with the flipper again, it's rotating the crank and link underneath the playfield, but it's still loose enough for me to be able to slide it.

So our goal is to try and align the tip of the flipper with this small indentation on the playfield.

The next step is a critical step and that is getting the end play between the flipper crank and link and the flipper bat set uh so it isn't binding up against the bushing. I'm going going to use um two uh credit cards, take these and slide them underneath the flipper and what that will help with is keeping that spacing close. Again, trial and error might be the best way to get this right.

So now that we have the credit cards in place to kind of set that uh depth, the the play, I'm going to raise the playfield back up. That point it's a little bit easier to tighten up the hardware. With the crank being tightened down, the flipper shouldn't move. But again, trial and error, we're going to need to kind of be on both sides while we're working on tightening this down.

I'm going to rotate the flipper ever so slightly so the crank is not resting against this rubber stop and I'm going to feel for the end play and I can feel just a slight amount of up and down play. That's what we're looking for—um, sort of about two credit cards widths, a very small amount. I feel like I've got good end play before I tighten it down and drive it home. Going to double check that the flipper hasn't drifted off of the mark. If it has, give it a teeny adjustment. We're going to try and get our tool here on the screw and we are going to tighten. Once we give it a few tight uh turns, again we're going to go back on the other side of the playfield and double check to make sure that the flipper is still on its mark. It is still on its mark, so we're good.

At this point, we are going to just kind of drive it all the way home. As I tighten this screw, I am holding the crank and link uh pushing it up against the rubber stop here to keep it in place so it doesn't want to rotate or shift when I am trying to tighten the screw down.

Once we have it tightened down, we want to double check our flipper end play. We want to make sure that this adjustment is still good. Again, trial and error and feel. I can see this is moving a bit. I can also hear a slight clunking, just a little bit when I move it up and down. That's how I know that I have just enough end play in this flipper. If I can see this thing moving a lot, too much, you need to go back in there and you need to set that end play right. If you don't see it moving a lot, or hear it move, it is too tight and it's going to bind. You'll need to redo it and get that proper amount of endplay.

Once the flipper crank is tight, once we've confirmed we have uh enough uh free play, the last thing we want to do is make sure that the end of stroke switch is not interfering with the flipper crank at all and that when the flipper reaches its end of stroke, this switch actuates. Just a little bit here, we're looking for the switch to be open, maybe an eighth of an inch uh once the flipper is at its full stroke.

With everything back together, the next step is to put the playfield down and play a couple test games. Remember, the things we're looking for: if the flipper starts to drift upwards, we need to get back in and retighten the flipper bat shaft in the crank. If it is starting to bind or it feels like it's getting stuck or not returning back to its rest position, that might mean we do not have the free play set correctly. So you'll have to readjust that.

Thanks for watching another Stern Tech School video.

_(Acquisition: youtube_auto_sub, Enrichment: v1)_

---

*Exported from Journalist Tool on 2026-04-13 | Item ID: f1b38e4e-aa2a-48f4-8229-090297cc5273*