Borbin the 🐱

The original 4th gear is 26/20, while the new one is 24/22. The input shaft side of the 4th is 2 teeth more, and collides with the reverse shifter.

The reverse shifter needs to be adjusted to make room for the wider 4th gear.

Check the clearance with grease.

The new 3rd and 4th gear for the output shaft are slightly thinner as the original gears.
To compensate for this, spacers need to be added to have the new gears aligned.

Fabricating spacers with an exact thickness and inner diameter can be difficult. For my new gear set, I cut them from 12L14 round stock.

The exact thickness is machined while keeping a small ridge to hold the part.

The final inner diameter is set and cut. This separates the part.

The new spacers are cut.

The position at the input shaft for the 3rd gear is usually not oversized so the 3rd gear could be easily pushed through and rotated to fit the 4th gear.
But I don't like any not-fixed part on the input shaft. It will just loosen over time and start wearing out. So thats why the input shaft is at a constant 3/100 oversize.
But twisting the 3rd gear was actually more difficult than I thought. Once the 3rd gear was pushed a bit on the shaft, I tried to make a small angular adjustment. I used a larger wrench made out of a high quality plastic to not scratch the gears. The wrench broke, and I had to come up with a different approach.
I fabricated two square holders that are connected with a 3/4" acme threaded rod to twist the gears. I made sure there would no breaking this time, and as it turned out, the aligning of the gears using the screw was easy.

The parts:
The square frames were cut out from a saw blade for additional strength using a plasma cutter.

The inside of the square holder were cut on the saw to match the gear pattern, and then filled with JB-Weld, and then pressed on the gear while still wet for a perfect fit.

The Mega-Twister is ready.

I used axial bearings to take the load sitting on small curved stainless steel rails. Slightly over-engineered, but it worked so smoothly.

Used a piece of plastic to keep the distance between 3rd and 4th during the angular adjustment.

The input shaft should have a 0.2mm clearance.
First start with the measurement from the bearing to the housing.

Take the measurement of the depth of the bearing reception.

The gasket is available in two different thicknesses, so make sure to measure it.

Now adjust the position of the bearing. Moving the bearing to the measured length can be challenging as the bearing does not slide but rather jump in steps. To solve this, place a gauge block with a feeler gauge of matching thickness between the bearing and the gear as a stop block. Adjust the gauge size for each measurement cycle to achieve precise positioning.

Check the measurement again and verify the play with the cover and gasket (dry) on.

The same for the output shaft to make sure the smaller back cover does not push against the bearing and also has a 0.2mm clearance.

The oil catch disc is located between the 1st gear and the bearing on the input shaft.
Needs to be fabricated because there would be too much damage to the old one when pulling off.

The disc gets fabricated from a piece of sheet metal on the lathe: