Bultaco Pursang Service Center: Transmission

 

If you have your transmission apart it's best to replace the bearings, replace any worn shifting dogs on the gears, and modify your shift drum to eliminate missed shifts.

Topics:

Bearings

Worn Shift Dogs

Modify Shift Drum

Clutch

 

Bearings

Replace the bearings if you have the transmission apart.

Bearings:

Clutch Hub (1) $32 4205 (Double Row Bearing)
Lf Countershaft (1) 6205
Rt Mainshaft (1) 6303

Rt side Countershaft
Lf side Mainshaft (2)

6202
Crankshaft (3)`0 6205

Seals:

Lf. Countershaft Seal (1) ?30? x 40 x 7
Rt Mainshaft (1) 25 x 35 x 7
Lf Crank Seals (2) 25 x 40 x 7
Rt Crank Seals (2) 32 x 47 x 7
Shift Shaft Seal (1) 14 x 24 x 6

O-rings:

Rt Main Collar (1) ~23mm x2mm
Rt. Crank Collar (1) ~23mm x2mm
Lf. & Rt Crank (2) ~55mm x 2mm
Lf Counshaft Collar (1) ~18mm x 2mm

Worn Shift Dogs

Modify Shift Drum

Hughs Bultaco and Woody's both offer a Modified Shift Drum to reduce missed shifts. (~$125)

or
Use this template to mark the cam on your shift drum. Then grind down the cam to remove the flat areas off of the lobes. Polishing the surface afterwards helps considerably. Definitely purchase the stiff detent spring from Hughs to replace the stocker.
(from C. Otero)

 

                     

Clutch

Tighten pressure plate nuts until they bottom, then back off 2-1/2 turns. Pull clutch lever in and kick over to check pressure plate runout... adjust nuts until the plates run true.