Continuation from the last timeNow, let's assemble the MP5K PDW High Cycle that was requested.

First, we'll start by working on the gearbox.

Preparing the gearbox

First, use a rotary tool to round off the corners of the rectangular cutout at the front of the gearbox where the cylinder is housed.

The purpose is to prevent the gearbox from cracking, but since I don't perform adjustments that put that much stress on it, it might be pointless, but I do it for peace of mind.

The rotary tool and bits I'll be using. By the way, the rotary tool is my wife's, used for nail art.

Even something this flimsy can perform sector cutting. The price is probably around 1500 yen?

After processing (red circle in photo)

Gearbox left side case

Right side case of the gearbox

If you file it down too aggressively, that will cause problems, so I think it's enough to just round off the edges.

However, although it's not visible, please make sure to carefully remove any sharp corners on the back.

Next, we'll sand the parts of the gearbox where the moving parts make contact with each other using sandpaper (#1000). These areas are the cylinder sliding surface, the tappet moving surface, and the cutoff moving surface.

Some people say that polishing is pointless, but I do it anyway because it's more of a psychological thing.

The area highlighted in red in the photo is the polished area.

Right side case of the gearbox

Gearbox left side case

If you overdo this, the dimensions will change, so it's best to leave just enough of the base metal showing.

Next is the switch.

switch

First, check the switch.

I apologize for the poor image quality, but it's a little burnt.

The owner has been using nickel-metal hydride batteries until now, so the damage won't be too severe, but it seems that it will still be damaged.

Polish it with a file. Apply contact protection grease when reassembling.

I use Lonex copper grease.

LONEX Copper Grease
It seems like a good idea, but these days FETs are more common, so it's not used much anymore.

Since we plan to reuse as many other parts as possible this time, there are no other parts that need to be cut or polished, so we will clean all the parts here.

In cleaning, IWash with a neutral detergent.I don't use chemicals like parts cleaner for cleaning.

In fact, industrial rubber often contains oil in its material composition, so using degreasing chemicals will degrade its performance..

I've had some pretty rough experiences at work, so I'm very careful about what I do.

シム調整

Next, we will adjust the shims.

I generally work with the bevel gear as the reference point, so I assemble the gearbox, grip, and motor that the bevel gear faces and measure the gap.

Here's my own method:A thickness gauge is used to measure the gap.Originally intended for measuring tappet clearance on motorcycle engines, this tool is used for shim adjustment.

Since it's a tool that can measure gaps, you can measure the gap between the gears and the gearbox, allowing you to adjust the shims with fewer trials.

Thickness gauge

シム調整

Insert a thickness gauge between the bevel gear and the gearbox to measure the gap and determine the appropriate shim size.

The other gears are adjusted so that their meshing is maximized.

For the bevel and pinion gears, find the position where all the pinion gears mesh together and fix them in place.

Now that the Sims are decided, I'll write them down on a piece of paper so I know where each Sim goes.

My personal method for adjusting shims is described here.

Cylinder, piston, spring

The cylinder and spring were of unknown origin, so I got permission from the owner and replaced them with aftermarket parts that I selected myself.

For the cylinder, I chose the Laylax Stainless Hard Cylinder Type F (barrel length 110mm-200mm), and for the spring, I selected Airsoft97's original unequal pitch spring M90.

LAYLAX Stainless Steel Cylinder Type F  
This is a standard cylinder part.

Airsoft97 Unequal Pitch Spring M90
I think these are good springs for the price.

The cylinder was clean with no burrs on the acceleration port. The spring was also of good quality with neatly finished ends.

assembly

Now that the preparations are done, let's quickly assemble it.

This time, I didn't use any parts that I was unsure about the compatibility of, so I assembled it with just the bare minimum of checks. For the grease, I used Tokyo Marui's genuine high-viscosity grease and silicone grease.

Assembled gearbox

Securely attach the SBD to the motor.

Eagle Model SSB Super Sparkster
The SBD is a bit overkill for the EG30000HC motor, but it gives me peace of mind.

By the way, I've included an explanation of the operating principle of SBDs, so please take a look if you're interested.

All that's left is to assemble it into the receiver and you're done.

Inner barrel

While I have it disassembled, I'll replace the hop-up packing with a new, genuine Tokyo Marui one.

While I had it disassembled, I lightly tapered the tip of the barrel using a rotary tool and a rubber grinding wheel.

Apply Tokyo Marui high-viscosity grease to the barrel's packing mounting area (do not apply it near the hop-up window).

Install the hop-up packing, apply a little grease to the outer circumference of the hop-up packing, and then assemble it.

Later on this blog, I will share my own method for assembling a chamber that produces good performance.

Tokyo Marui Genuine Hop-Up Packing Set
It's a classic

Complete

All that's left is to assemble the remaining parts and check the initial velocity and rate of fire (the conditions are the same as before: 2g bio BBs, slight hop-up).

Before maintenance, the muzzle velocity with 0.2g BBs was in the 62m/s range, so it increased by about 7m/s.

Hop 0 under the above conditions

The muzzle velocity wasn't as high as expected due to the short barrel, but the owner was happy with it, so the job was successfully completed.

The initial velocity has increased, but the rate of fire hasn't changed much, so it's a great success.

If you're interested, please also check out my review of the chronograph.

The owner also requested a suppressor attachment, so I installed a suppressor attachment from Laylax.

- Suppressor attachment
I think this is probably the only option.

Then I attached some supplements I had at home, took some pictures, and that was it.

I think it's pretty cool.

Tokyo Marui High Cycle Electric Gun MP5K

I have now successfully completed my work.

I'm glad to hear that the owner later took it to an airsoft game and it worked well.

That concludes the maintenance guide for the Tokyo Marui MP5K HC.