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                      USPD Pinion Sprocket Change 


1) Use a 6mm Allen wrench to remove the three bolts holding the motor to the gear
housing of the drive system. Pull the motor straight out from the housing. Note the flat
spot on the motor shaft. When re-installing the motor, be sure this flat spot is aligned 
with the flat spot in the gear at the center of the drive. Remove the aluminum "gasket" 
from between the motor and housing. (see below)

NOTE: The aluminum "gasket" is ONLY required when installing the "silver can"
motor shown in the picture below. All other motors (BMC, MAC, Kollmorgen)
must be installed WITHOUT this "gasket".


2) Remove the four screws holding the planetary gear set in place. (below)


3) Lift out the planetary gear and set aside. (below)


4) Locate and remove retaining clip on the chain master link. Remove chain. (below)


5) Turn the housing over and remove the sprocket assembly being very careful to note
the position of all spacers. Draw a diagram to help you remember the order in which
these parts are assembled on the splined shaft!  

NOTE! The are two types of pinion sprocket assemblies used in Currie USPD drives.
 1)  Picture A is the .500" or 1/2" older type
Picture B is the 12mm newer type

                  *There is only one type for a
Lashout bike,  picture A.
                  *Rayos and Electrec use the 18mm type not shown here.


A ( Order of parts L to R = Nylon, sprocket, Nylon, steel, snap ring, steel)

 B         (Order of parts L to R = Nylon, sprocket, steel)

6) Remove the Nylon spacers, sprocket, and steel spacer(s) from the drive shaft. Install the
new pinion sprocket with the Nylon and steel spacers in the same order as removed. (see 
below) Be sure the splined (grooved) end of the shaft, Nylon spacer, sprocket, and steel
spacer are in the exact order shown above! NOTE that the pinion sprocket "teeth" are 
offset to the right. (away from the splined portion)


7) Insert the new pinion sprocket assembly back into the housing making sure the steel 
spacer remains on the drive shaft! (it can fall of and lodge under the pinion if you're
 not careful)


8) Do NOT install the chain yet, since it will installed last. Re-assemble the rest of the 
drive unit in the same order it was disassembled. 

***All custom sprocket combinations vs. chain length (click)

9) The chain may need to be lengthened or shortened depending on whether you installed
a larger or smaller pinion sprocket. If you're unfamiliar with this process, refer to "Changing
the Length of a Chain" in the kit index for assistance. When replacing a stock 19T sprocket
with a 21T or 22T sprocket it will be necessary to add a "half link" to your chain. Here's
how to do that:

9a) To increase the length of the chain, it is first necessary to remove a link. Do this by carefully tapping out the appropriate chain pin with a small punch and hammer. The picture below shows the original length chain, (top) and the resulting chain length. (bottom) NOTE: A "link" consists of 2 segments. (holes) The picture below shows exactly which pin to drive out in order to remove a single link. NOTE: Try using a vise as an "anvil" to aid in removing the pin. Place the chain on top of the closed vise jaws, then open the jaws just wide enough to allow the pin to be driven down between them.

9b) Replace the chain around the rear sprocket. Using two master links and a "1/2 link", as illustrated below, connect the chain ends. When the chain ends are linked, the resulting chain will be longer than the original chain by 1/2 link! (one hole) This additional length is necessary to accommodate the increased pinion size.

9c) If you are unable to achieve the correct chain length you may need a chain block which provides a greater degree of adjustment than the stock part allows. See below:


EVDeals Delrin Chain Block Installation 

                             ChainGuideDelrin.jpg (51764 bytes) 

Your adjusting block can be installed in any one of four 
orientations. i.e., there is no "right" way to position the 
block. Select the positioning that best suits the condition 
and tension of your chain. The object is to remove all but 
a small portion of the chain slack without causing binding.
Place the adjusting block into position and determine the 
best orientation. Install the chain block using the original 
washers and bolt. If necessary, you can place one or two
washers under the block to provide proper clearance. 
Before tightening, rotate the wheel and be certain that the 
chain moves smoothly over the block. 

The picture below shows how the Delrin block is positioned
to guide the chain smoothly between sprockets of a Currie 
USPD bike drive unit. The same positioning applies to
all Currie scooter drives. 



HINT: The chain can be fed through the opening on the side of the drive assembly 
AFTER the drive unit is fully assembled. Feed one end of the chain into the opening 
adjacent to the pinion gear. By turning the gear with your finger, the chain will be dragged
around the gear and return out the same opening. 

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