The Evo two speed transmission is not only a marvel for being the first in the industry. It is also reliable, easy to maintain and relatively easy to understand (in comparison with complicated CVTs found on larger scooters). This guide will show you a few modifications that can be made to both improve the performance of the transmission and lengthen the lifespan of the mechanisms.

No modification will replace preventative maintenance. For suggested preventative maintenance, see Evo two speed transmission maintenance.

Replace the shielded bearings with sealed equivalent Edit

Evo two speed bearings in cam

Sealed bearings pressed into bearing holders of transmission

In order to replace all of the bearings in the transmission, you will need 10 bearings.

  • 4 x 6000 10x26x8 Ends of top shaft and belt guide (C4-5 3COB06000A 10x26 BEARING)
  • 2 x 6001 12x28x8 Inside cams of top shaft (C4-3 3COB06000A BEARING 28x8)
  • 2 x 6002 15x32x9 Inside caps of bottom shaft (C6-2 3COB06002A BEARING 30x15)
  • 1 x 6204 20x47x14 Inside lower 2nd gear (C8-3 3COB06204A BEARING 20x47)
  • 1 x 1910 10x19x6 Inside cover clutch plate (C8-5 3COBL1910A 6x19 BEARING)

Buying a decent set of sealed bearings should run you somewhere around $50. Installing these bearings should be generally straightforward except in the case of a couple press fitted bearings. For tricks on removing press fitted bearings, see the guides to installing and removing pressure fitted parts with heat and removing the Evo clutch plate bearing.

Seized bearing and destroyed shaft

seized bearing next to the shaft it destroyed

Melted nylon cam

nylon cam destroyed by seized bearing

Seized bearing

seized bearing with disintegrated ball bearings and cage

Increase the grip of the 2nd gear clutchEdit

The 2nd gear clutch engages the 2nd gear through the use of pressure and friction. There are a couple problems which you can address that will increase the amount of friction that this clutch can develop with less pressure. By taking these steps you can not only increase the performance of the clutch, but its effective lifespan as well.

Evo transmission clutch with oil

grease slathered clutch plate

The 2nd gear pulley bearing that comes with the transmission is a large 6204 shielded bearing that releases its lubricant all over your clutch plates. This a very serious problem since you want these plates to stay as sticky as possible.

There are two solutions to this problem. You can either replace the bearing with a sealed bearing that doesn't release its grease or you can remove the grease from the bearing that is already there.

Sealed bearing and 2nd gear pulley

sealed bearing ready to be pressed into 2nd gear pulley

Replace with a sealed bearing (recommended). It is quite easy and cheap (about $9) to simply replace this bearing (6204 20x47x14) with a sealed bearing which will not release its grease. Once you have a replacement bearing, the process can be completed in less than an hour using the installing and removing pressure fitted parts with heat to free the old bearing from the gear.

Shielded bearing in gas

2nd gear pulley in gas

Soak the grease out (not recommended). A common solution to this problem is to simply remove the grease from the shielded bearing all together. This can be achieved by leaving the bearing and gear in a container of gas over night. The grease should be release and the bearing will sling no more. Though this approach is unnerving, many have tried it with no reported ill effect.

Annealing clutch plate

clutch plate being heated to soften metal

Anneal and polish the clutch plates. You can effectively make the clutch plates "stickier" by heating them up and making them softer. This can very simply be achieved by heating them up until they are cherry red, letting them cool and reinstalling them in the scooter. A butane torch or gas stove is usually the most effective method of doing this. The weakening should be mild enough to not effect any of the other properties of the plates.

See the guide to annealing clutch plates.

Improve the location/adjustability of the shifter cable Edit

Normally, the shifter cable runs into the transmission and is clamped below the transmission. This location is entirely out of reach for adjustments once the transmission is installed. With a bit of hole widening, the cable clamp can be moved to the more accessible front side of the transmission.

See the guide to relocating the Evo two speed transmission shifter cablewe

Lighten/Strengthen 1st gear pulley Edit

There are several 1st gear pulleys that have popped up. The most common is the solid aluminum gear. In some cases, the solid aluminum gear was traded for a similar gear with a steel sleeve pressed in for the bearing to grab more effectively. Some gears have been custom machined to lighten their rotation, but the newest, lightest and most indestructible gears appear to be heavily machined steel gears. These new steel gears are starting to appear in the new transmissions that are still available from the factory.

If you were intending to lighten the gear yourself, you must use a precision machine in order to maintain the balance of the gear. Otherwise, you could contact Evo's warranty service for information on purchasing newer gears. Unconfirmed accounts suggest that these gears go for around $50.

Evo steel 1st gear

newest steel 1st gear pulley

Evo lightened 1st gear

custom machined 1st gear pulley

Evo strengthened 1st gear

1st gear pulley with steel sleeve