After less than a year riding my Kawasaki Ninja 400 (EX400 2018 model), I noticed that the rear turn signal bases where becoming soft then eventually failed. They are made out of semi-hard rubber that eventually softens and turns into this gooey-like substance and eventually makes your signal light fall off. The turn signal light itself won't fall while riding because it will dangle by it's wiring. Keeping your bike in long-term storage also does this. So off I went to the local dealer and bought replacements (the whole signal light assemblies).. a few months later it happened again, it became this gummy mess and broke off again. Whatever rubber material Kawasaki used for that part was definitely not well-thought of. Even my riding pals had the same problem with theirs.

So I decided to design this "replacement" because I don't like spending money on parts that keep failing. Worse was there are no after-market replacments (that or I change the whole tail light assembly which is more expensive). I did this modification back in 2018 and so far it has held very well for 6 years now, my bike has gone 30 thousand kilometers since then without any problem. I used PETG material printed with 100% infill and 0.12mm layer height using my trusty Ender 3 V2.

This one is a direct replacement for the rubber boot only (base) of the original turn signal. You will still need to have the original turn signal light itself as you will re-use it's undamaged plastic parts.

1. Print 1 each of the Left and Right Bases, then print 2 pcs. of the Lock Plate. Clean out the prints, remove strings and run a 3mm drill bit thru the holes. Ensure to remove all internal supports.
2. Run to you local screw shop, get (4) M3x15 scket head screws, (4) M3 Nuts, (4) 3mm x 9mm x 1mm flat washers.
3. Insert 2 M3 nuts inside the recess of the bases, this is where the 2 M3x15 socket head screws will lock on to.
4. Remove the damaged signal light, since it has failed already, just remove it's wiring from under the pillion seat of the motorcycle and unwork it to be able to pull it out. There will be metal clamps that hold the original rubber base, remove them now also.
5. There will be a large philips-head screw securing an almond-shaped mounting plate retainer - take this out and set aside as you will be re-using this.
6. CUT the terminal plug as it will not permit the mounting plate to come free. Once cut set it aside together with the mounting plate.
7. Pull out whats left of the old rubber base and discard. Clean whatever gooey matter it has left from the other parts.
8. Insert the wiring thru the new 3D-Printed part and insert the outer end to the stem of the signal light. If your printer prints to within the usual tolerances, this should be a nice and snug fit.
9. Inser the metal mounting plate and secure it using the large philips-head screw removed earlier.
10. Put some threadlocker into the M3 nuts you installed earlier (through the holes), then install/push the on the original mounts on the motorcycle. The lock plate goes underneath and you use the M3x15 screws and washers to hold and lock the new signal liight bases in place.
11. The contour of the base will match what is on the motorcycle. Make sure to identify the LEFT against the RIGHT hand signal lights.
12. There are ARROWS on the 3D-printed locking plates, ensure they point FORWARD of the motorcycle as their overlap matches with the shape of the inserts of the base.
13. Re-connect the terminal plug you cut, put some insulation and re-rout the wiring back under the pillion seat.
14. Test for function, RIDE your motorcycle, enjoy it and forget that you ever did this modification because you will never have to worry about your turn signal lights falling off again..

• Print the parts using the original orientation of the STL as this gives it it's maximum mechanical strength - I used PETG and it held very well all these years as it is good at resisting the elements but you can also try Nylon. Whatever you do don't use PLA or ABS.