Bridgestone Motorcycle Parts Discussion Board

Moonpup, my question as well, though 3yrs later.  What went wrong?  I think this would be very interesting to have.  I might have originated from Rushville IN, but now want to show as Brisbane, Aus.
Cheers, Mike.

Hi Joe,

13/16" AF (Across the Flats) is the size socket you need to remove or refit standard spark plugs in your HS175.
This is a very common spark plug hex size used in older engines. Use a proper Spark Plug Socket which has a a rubber insert inside to stop you breaking the porcelain insulator of the plugs which is hard, brittle & easily cracked.

Thanks to the long history of engine and spark plug development the sizes & threads used for plugs are confusing.
The thread of the spark plugs is Metric (14mm x 1.25) as is the terminal for the HT lead (M4 = 4mm x 0.7) but the hex for the socket is Imperial (13/16").

Best Regards,
Mike Munday (also HS175 owner),
Australia

        Sounds like a plan, it relatively simple.
      I disconnected the white wire from the rectifier, then separated the bullet connector on the brown wire coming up from the alternator.  Then made up a short connecting wire from the alternator brown to the white terminal on the rectifier.
      I taped together (but not electricaly connected) the now redundant white and brown wires running back from the ignition switch and tucked then safely out of the way.
      Apologies if the above is obvious to you, it may help others.

Hi Marcus
       Sounds like your GTR has been fitted with a 5 wire ignition switch from the 175/200 models (these are more readily available and cheaper).
         As far as I can tell, the 350 has an extra circuit, which swiches in the 3rd phase of the alternator when the lights are in use for extra power. This uses the brown wire from the alternator which the switch connects to the white wire to the rectifier.
          Your horn should be connected to the battery using blue wire as shown in the GTR wiring diagram. It needs battery power to work properly. There may be a spare blue socket on the switched live coming from your switch, if not splice it in.
    Unfortunately the wiring diagram for the 175 in the manual on this site is not colour coded so it is difficult to compare the 175/350 circuits.
         Try this - connect horn as above. Connect the brown and white wires together (near the rectifier where they meet). This effectively bypasses the ignition switch and gives a useful battery charge boost.     
          Alternatively, buy a 6wire GTR switch.  Richard shows 1 in stock but Kerry Pagenkopf (facebook site) may have also have a new or good used one. I bought one from him recently.
            Brian.

Edit.      From a colour coded 175 wiring digram that Mike Dunham sent me (Thanks mike), the 175 switch shown does have a brown wire and shows 7 connections from the switch. So I,m not sure now what switch you have. Mikes wiring diagram also varies from the one shown in the on-site manual and may be a later 175 wiring update which does include brown/white wires for switching in the 3rd alternator phase.  However, I believe the suggestions I made above should still work if you have previously run the bike with the fitted 5wire switch.

Yes, found them. Thanks!