Author Topic: Bridgestone 350 (175/200's too) Electronic Ignition Conversion  (Read 10947 times)

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Offline OldSwartout

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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):
« Last Edit: August 23, 2014, 08:23:41 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #1 on: August 23, 2014, 07:11:21 PM »
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.

Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #2 on: August 23, 2014, 07:13:38 PM »
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:
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #3 on: August 23, 2014, 07:23:21 PM »
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.

Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #4 on: August 23, 2014, 07:26:26 PM »
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.
« Last Edit: August 23, 2014, 07:40:28 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #5 on: August 23, 2014, 07:30:01 PM »
Mount the pickups and point cam/rotor and connect the pickup wires to the harness wires in the alternator. Connect the new power wire (blue) to both red wires to the pickups. Connect the other wire from the right pickup to the black harness wire and the left pickup to the white harness wire. The color of the wires from the pickups varies, depending upon the model of Dyna S purchased. (Ignore the Black and White color wiring connections in my photos, they are reversed. Oops).  Attach the harness ground wire (if still using the internal ground wire). 

« Last Edit: August 23, 2014, 07:42:56 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #6 on: August 23, 2014, 07:33:04 PM »
Preliminary timing adjustment:
Set the engine to one cylinder firing position using the timing pin or dial indicator (.135 in./3.44mm BTC). Then with the set screw loosened slightly, rotate the rotor until the magnet visibly lines up with the bump on the ID of the pickup, then tighten the setscrew to lock it in place. Note: I suggest you pull the rotor out at this stage and apply Loctite to the ID and to the setscrew. You will have time to make adjustments before the Loctite sets.

Reconnect any remaining disconnected wiring back to the 350 wiring harness under the seat. The blue power wire (or re-purposed black/white wire) will connect into the harness blue power wire. Mine had an extra open spot in the 4-way connector under the seat, but you may need to just splice it in with a crimp connector.  Reconnect the white & black ignition wires, the brown alternator wire, and bluegreen and yellow to the rectifier. Don’t forget the ground, either the original black/white or your new ground from the engine case must be connected back to the battery ground or frame.

Final timing is similar to points except you can’t use a test light. Instead, watch for a spark. It is easiest with one of the ignition test gap tools available at auto parts stores for less than $10, or open the side electrode on a spark plug straight out because you can easily see and hear the spark. Set the engine crankshaft to the correct timing location using the timing pin, then with the transmission in gear (5th or 6th  ) and the ignition on, rotate backwards, then back forward slowly. It should spark just as the pin drops into the crankshaft notch or the piston reaches the correct distance BTC. Adjustment can be made by loosening the setscrew on the rotor and moving it, or rotating the alternator. Once one side is done, adjust the other side by moving the pickup as necessary. This may be a little more tedious than adjusting points, but once it is done, it should not require maintenance unless you move the alternator (no more point gap filing or adjustments).
« Last Edit: August 23, 2014, 07:59:59 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #7 on: August 23, 2014, 07:35:20 PM »
To double check your timing you can use an automotive strobe timing light. Due to the small diameter of the rotor, it’s difficult to get an accurate visual mark alignment across the gap to the pickup, so I made a crude pointer and placed timing marks on the OD of the alternator using the timing pin notches.
« Last Edit: August 23, 2014, 07:49:39 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #8 on: August 23, 2014, 07:37:02 PM »
Nice Spark:
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline OldSwartout

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Re: Bridgestone 350 Electronic Ignition Conversion
« Reply #9 on: August 23, 2014, 07:57:06 PM »
Additional notes:
  
If your spark is erratic, be certain the rotor is set deep enough on the old point cam to align the magnet with the axial center of the bump on the pickups. I didn't realize this at first, so most of my photos show the rotor located at the end of the point cam in error.

The Dyna web site has a brief troubleshooting document.

Dyna requires 3 Ohm or higher resistance coils.  The BS350 coils are roughly 5 Ohms, so they should be fine. Aftermarket coils, Dyna or others, could be used for an even hotter spark.

There is a photo in the gallery section of a conversion I did to a 175 with a 1/2 speed alternator, which requires a 2 magnet rotor and a special shortened pickup. http://bridgestonemotorcycleparts.com/index.php?action=gallery;sa=view;id=291  I modified a KZ1000 system, but it would be much easier if you purchased a Dyna S system for the Honda GL1000, which comes with the 2 magnet rotor and short pickup.  For a 175 or 200 with the engine speed alternator, the conversion is similar to the 350.
« Last Edit: August 23, 2014, 08:10:52 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline slawsonb

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Re: Bridgestone 350 (175/200's too) Electronic Ignition Conversion
« Reply #10 on: August 24, 2014, 01:22:36 AM »
Nice. You've been a busy boy! Will take a while to digest all of this, but looks very interesting and doable. Thanks for the very thorough description/instruction.
...bert
« Last Edit: August 24, 2014, 03:30:56 PM by slawsonb »

Offline mybridgestones

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Re: Bridgestone 350 (175/200's too) Electronic Ignition Conversion
« Reply #11 on: September 19, 2014, 09:49:48 AM »
Hi,

Great information. I had a Dyna conversion on my HS 175 years ago and it worked perfectly.

At the moment, I'm trying to get another one done, but the bloke that did it before isn't available, so I can use this information for when I ask someone else.

Well done!

Stu

 


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