Forum > How To

Bridgestone 350 (175/200's too) Electronic Ignition Conversion

(1/4) > >>

OldSwartout:
Bridgestone 350 Electronic Ignition Conversion adapting a Dyna S ignition to a Bridgestone 350.  The same basic process can be used on a 175 or 200.

The Dyna S ignition adaptation to a Bridgestone 350 is relatively easy to do, but requires a minimum amount of machining with a lathe.

In addition to basic hand tools, you will need the following:
1.   Dyna S ignition that uses two pickups and a single magnet rotor. This can be one of many models, new or used.  I have made two conversions using the KZ1000 unit which seems to be plentiful used on Ebay for less than $100.
2.   4-40 tap and #44 drill bit
3.   3/16 -24 x 3/16 long set screw
4.   Access to a small lathe or a friend with one (or machine shop)
5.   Heat sink compound available at Radio Shack and electronics stores


This is what I bought:

Dyna S DS2-1 unit for a KZ1000 (used):

OldSwartout:
Remove the pickups from the backing plate and carefully cut the shield off the wiring. The screws are 4-40 socket head screws.

Remove the points and point backing plate from your 350 alternator. Clean up the backing plate as needed, and use the Dyna S plate to mark the screw holes for your BS backing plate. Drill and tap the BS backing plate with 4-40 holes at the marked locations.

OldSwartout:
Now, there is a decision.  The Dyna S system needs one more wire than the BS points needed. The points used one wire each from the coils. The Dyna S system uses one wire to each of the coils, but also a single 12V wire feeding the pair of pickups. There are two options:
1.   Add a wire to the wiring harness from the alternator to the frame. This option requires removing and disassembling the alternator.
2.   Repurpose the existing ground wire in the alternator harness and add another ground wire externally to the alternator. This will leave your bike not quite original looking.

 Your choice depends on your concern for “originality”.  The second choice is by far easier.

For choice #1, remove the alternator per the service manual:
1.   Disassemble the alternator by removing the two long screws on the outside diameter.
2.   Tap the drive end housing loose from the steel center laminations/copper windings.  The armature will come out with it.
3.   You are left with the points end housing and center section. Tap those apart slowly. You must feed the wiring harness back through the external housing as it comes apart. 
4.   Once apart, cut the shield off the harness, cut a 16 ga wire with a little extra length, place it with the original wires and then re-wrap the harness. ½“  heat shrink tubing will let you pass the harness connectors through if you stagger them. Since the new wire will connect to the blue circuit in the main harness, use blue wire if you have it.
5.   Carefully reassemble the alternator and reinstall. You may actually want to install the Dyna S pickups, complete the wiring in the end of the alternator and install the rotor while it is out on the workbench.

For choice #2, add a separate ground from the engine to the frame
1.   The existing ground for the alternator is a black/white wire fastened to the alternator inside near the condensers and connected to the base of the rectifier where it mounts to the frame.
2.   This wire can be disconnected from the frame and alternator, connected to the red wires on the pickups and the blue main harness wires under the seat. My bike actually had a spare opening in the 4 way junction connector.  I’d suggest marking the wire on both ends with some blue heat shrink or tape to avoid future confusion.
3.   You must replace the ground with a new wire. There are a number of possibilities, but I’d suggest using an eyelet connector under the 8mm case bolt at the rear of the engine next to the frame backbone, then run the wire up along the backbone and ground it like the original wire. This will keep it nearly out of sight.

You will need to modify the point cam and the Dyna S rotor so you can mount the rotor to the alternator shaft. Depending on the model of Dyna S you get, the rotor will vary. The KZ1000 rotor is .600 in. ID, so the point cam can be turned down to that diameter, leaving a thin wall to hold the rotor. The point cam can’t be turned much smaller, so it may be necessary to bore the rotor you have larger.  For the KZ1000 rotor, it was also necessary to cut part of it off.

Original and reworked point cam and rotor:

OldSwartout:
Mark the rotor magnet position on the end of the rotor with an easily visible mark to make alignment for timing easier. Tap the rotor for a setscrew 90deg either direction from the magnet. The rotor will be mounted to the point cam and held in place with the set screw. Mount the rotor back from the outer end of the point cam approx. .050/.070 in.  The setback is necessary because the magnet must be located axially about the middle of the raised bump on the ID of the pickups, otherwise the triggering will be erratic.

OldSwartout:
Mount the point plate to the alternator approximately in the center of its adjustment. Don’t forget the heat transfer grease before you mount the pickups. Mount the pickups to the points plate approximately in the middle of their adjustment range. Be certain the pickup mounting screws don’t extend much beyond the back of the plate when tightened.

Navigation

[0] Message Index

[#] Next page