Some spacers and brackets for Ender 5 S1 to K1 hotend mod

To start off, I should say that I made these spacers for my own use. They are not perfect, and unfortunately I do not currently have the time to refine them. But, they do work. You should pre-read this guide. There's gonna be some tools you need, like very small hex keys (I think 1.5mm). You're gonna need various length m3 screws. You're gonna need m3 washers, too. This is not a complete list, of course.

The bl touch bracket is very nice (in my opinion). It is designed for M3 threaded inserts, so keep that in mind if you want to use it. Another thing to consider is that the cable for the bl-touch is not long enough to reach, so you'll need to make your own connector. I used this kit from amazon. Also, it is designed to be used without the fan cover. It serves no purpose, and is just extra weight, so you should remove it anyway. If your auto bed leveling is working great, you do not need to do this zero y offset mod. This will fix your ABL if the problem is a twist in the x extrusion. You will also need klipper so that you can modify the printer config to change the probe offsets. I modeled it after this.
 

Anyway, with that out of the way, let me give a brief rundown of the steps I needed to take to replace the hotend on my ender 5 s1 with the k1 hotend, found here at amazon.

First, print the spacers. Note that if you aren't going to do the zero y offset mod, you'll also need a spacer for your bl touch. The k1 hotend sticks down 5-6mm further, which is why we need these spacers in the first place. I do not provider a spacer for the bl touch in its original location. You should be able to just use longer m3 screws with a bunch of washers to act as a spacer.

Next, unload the printer filament and clean out what's left in there (as best you can). Remove the PTFE tube

Next, turn off and unplug the printer. Now, you need to unplug the part cooling fan, the throat cooling fan, the thermistor, the heater block, and the bl touch. These all plug in at the board on the back of the extruder assembly. Annoyingly, these connectors are hot glued on. You can peel it off, though. Do not tug on the cables too hard: you will rip them out of the connector end.

Now, take out the 4 screws that secure the throat cooling fan, then remove the fan. Now remove the part cooling fan (2 screws) from the back. Now remove the fan shroud (2 screws from underneath the assembly). Now remove the bl touch (2 screws, also underneath). Put all of these aside.

Now there are two screws that hold the throat cooler to the assembly. Remove them, then pull the block off. The PTFE tube should pull out of the extruder. You might need to press the tension lever in.

You might want to watch this video by creality to get an idea of what we're gonna be doing next: 

Now you're going to remove the heater block from the throat cooler. Take out the two screws, loosen the set screw, and pull the block out. This part was pretty difficult for me. I ended up mounting the throat cooler in a vise and slowly twisted the block back and forth while pulling with channel locks. I ended up bending the old heater block's throat, but I did eventually get it out. After you get it off, you need to clean out the hole in the throat cooler. I used alcohol.

Now, coat the throat of the new k1 heater block with silicone grease (that's what creality says to use, but I used CPU thermal compound). Insert the heater block into the throat cooler. Here is another problem you are going to run into to: The original screws are too long, and the ones that the k1 hotend comes with are WAY too long. If you don't put some washer on the screws before you thread them in, the screws are going to bottom out against the radiator fins of the throat cooler before it tightens up. So, yeah, put some washers on the screws. You're gonna need really tiny ones since these screws at something like 1.5mm. Do not over-tighten. These are tiny screws going into aluminum threads!

Now, here comes the hard part. The connectors on the k1 are different (EDIT: This is incorrect, at least for some models. I thought mine were different, but I'm being told that they're the same), and also the wires aren't long enough to reach when mounted on the 5 S1. So, I cut the two cables from the old heater block as close as possible to the block. Then I cut the cables on the k1 hotend as close as possible to the connectors (just toss those connectors). Then I skinned the wires and joined them together with solder, then taped. The heater block wires on the k1 hotend are coated wires (looks like copper, but there is a very thin coating). Use a lighter to burn off the insulation at the ends. Both the thermistor and the heater block are both just simple resistors, so the polarity does not matter at all. Just make sure that the two wires coming from the k1's thermistor go to the smaller plug (from the old block's thermistor). And that the two bigger wires go to bigger plug (from the old block's heater). I feel like this should be fairly obvious. If you don't feel comfortable splicing wires, or you just want a more professional result, you could consider getting a wiring kit like this one. Assuming the connectors for the 5 s1 and the k1 are the same, this will work well. As mentioned in my edit above, I've been told that they are the same. 

Now, just put it back together, using the two spacers for the part cooling fan. You can see where they go in some of the pictures I provided. I put some red electrical tape on the fan duct spacer to give it a good seal. You're also gonna need a spacer for the bl touch if you aren't going to do the zero y offset mod as well. As mentioned above, you can either design your own, or just use a bunch of m3 washers.

Once it is all back together and you've plugged everything back in, you're gonna want to do your z probe offset calibration. Make absolutely sure that the extended bl touch extends past the nozzle! If it doesn't, you need to add more spacing to the bl touch. If it isn't offset enough, the nozzle will hit the bed before the bl touch contacts. This would be very bad. Now, if you've spaced the bl touch too much, then it will hit before the nozzle when it isn't extended. That is also very bad. You're gonna want about 5-6mm of spacing.

I did this mod completely blind. All I knew was that it was possible because I saw a post on reddit. I made this guide from memory, so I make no guarantee that I didn't forget a step. Good luck!