I have Koga model Supermetro 2021 version bicycle. This is city bike made in Holland.
It is propelled via toothed belt instead of chain. 
Eight gears derailleur Shimano Nexus working on basis of planetary gear is bulildt-up in rear hub.
There is a dynamo in the front hub.
Front light of Koga Supermetro 2021 is directly built into handlebar pipe. This is solution made by company Light Skin. 
Similarly, the rear lighting is built into the seat post.
Koga Supermetro 2021 fenders are minimalistic.
Saddle Selle Royal Vivo Ergo
Ring Kong OI 
Bicycle specs:
Until 2016, Koga company used monoshock central shock absorber in Supermetro models, calling it in their bicycles Feather Shock. The last Koga Sumermetro model equipped with such a shock absorber is the 2015 version.
Feather Shock is a shock absorber with a small stroke of 3 cm for use in city or trekking bikes. Koga is constantly installing Fether Shock shock absorbers on other bikes of its brand, for example in the Koga F3 line, which is built on the same frame as the Supermetro.
Shock absorber from Koga F3 2021 is Feather Shock 2.0 version. The shock absorber is located just above the fork and is protected by rubber cover.
I decided to put shock absorber from Koga F3 to Koga Supermetro 2021. The Koga Supermetro 2021 bike should change as follows:
Before fork swap
After fork swap.
I bought used Koga F3 shock absorber. 
I shortened the steering tube so that it was the same length as on my bike. Just in case with saw I cut pipe 2mm longer than needed and filed it down to the final length in case the saw cut didn’t come out straight.
Fork with Koga shock absorber is heavier by almost 800 grams. 
I disasembed shock absorber to have bear fork for powder painting.
Fork after sandblasting.
Powder coated black (RAL9005) + glossy clear coat.
I changed the fork to Feather Shock absorber fork.
Koga Supermetro 2021 before and after fork swap.
I was missing plugs for the holes in fork for front rack mounting. I made model for 3D printer, but in the end I eventually got red plugs and painted them orange.
Ready bike
It is possible to by kit for Koga Supermetro 2021 consisting of fenders, rear rack, rear light and bike stand.
In Koga F3 and Supermetro bicycles rack connection to frame is hidden under mudguard, making the connection invisible. At the same time, rack is a support for the fender. Thanks to that rear fender does not need supporting bracket wire.
The front mudguard is connected to fork via dedicated front light holder. You need to screw lamp folder to the fork first and then you can screw the mudguard to holder. Therefore, a special adapter is added to the Koga Supermetro extension kit to replace this holder.
In the F3 series, Koga uses Eurofender Tempo mudguards with a standard spoiler (mud flap) and with widened version of the front mudguard bracket wire (Oversize Snello system). Additionaly, holes in the fender fit mounting with a rack connected to the frame with a profile under the fender. The front fender does not have a standard hook to connect to the fork, and the clip of the fender bracket has a Koga sticker instead of the Eurofender logo. These are lightweight composite fenders.
Instead of using fender support “Oversized Snello system” I bent the wire to look like „Normal Snello System” that was sufficient.
Front fork has special holes for inserting bracket supporting mudguard and a screw from the inside of the fork to block it. No adapters or holders are needed to attach mudguard bracket to the fork. It is a refined and nice solution.
Rear rack of Koga Supermetro and F3 models is a Tubus model dedicated to Koga. It has pre-drilled holes that allow to lead wires tof the rear lamp in them invisibly through the rack tubes. Rack tubes end so that the wires can go further in the rear fork tube, which has holes for cables specially prepared for this purpose.
In addition, the trunk is compatible with the Racktime system, which allows latching various types of containers and baskets from this system to the rack. You can put a spring or expander/rubber on the rack.
I like that rack is connected to frame under the fender, but I don’t like how much space is left in between fender and the wheel. Definitely it is possible to mount mudguard closer to the wheel without any risk that tire will rubb on fender. At least as close as it is between front wheel and fender on these bikes.
I decided to mount rear fender closer to the tire. For this purpose, I used rubber spacers to move the fender further from the mounts on the frame, replaced the screws with semicircular heads for screws with conical heads, and widened the upper part of the mounting holes so that the screw head could be hidden deeper and stick out less inside fender. I moved rack mounting holes where it connects with rear fork, so the entire rack could sit lower above the wheel.
very nice!
Hello. I am thrilled with your conversion. The photos of the disassembly of the Feathershock fork were particularly interesting to me. I would also like to disassemble my FeatherShock fork or change the setting, but I’m cautious. The yellow screw says not to open it yourself. How do you see that? Can you do that? What happens when you open the screw? Is that dangerous? How did you adjust the spring tension afterwards? Can this be done using the yellow screw or do I have to adjust the screws on the inside?
Screw does nothing particularity dangerous by itself – it must be in place and well placed for shock absorber not to fall into pieces while you ride. It is probably also used as regulation for setting up absorption strength as you can shorten space that springs have with it. Nothing shell burst on you suddenly if you remove it as it will be close to its maximum extension point if you start unscrewing the nut without putting load on absorber. But some people did reported me that they had difficulty putting it back in place. Maybe because you need to push down spring to set nut back in place.
There is yet another absorber nut at the other end inside fork tube. This one is not for regulation but for assembly.