Topic: 77 750a trans/fuel electrics

[shortbloke]

hi all,
just posted some info to Fran Fitzpatrick. I have much the same problem with high revs and stalling. carbs and ignition were ok . I`ve got 12v at the battery(new) but 10.5v at the changing relay.this seems to be a permanent  live feed which I don`t think should be there until the gear lever is operated.  there is a volt drop of 1.5v so I`ve a bit of resistance somewhere (10.5v should operate a solenoid) however when a direct feed from the battery is used the solenoid works ok. Is there a schematic drawing out there somewhere that shows how and when these relays and solenoids work. As with most wiring diagrams they are simply that....just spaghetti with no real info. Any ideas?

[raymond10078]

See some of the links at the top of the "A" page.

The 77/78 use a speed sensing device in the speedo - which operates the solenoid via a small circuit board (that is under the tank - but looks like a turn signal flasher).  There are instructions how to change the wiring of the 77/78 bikes to match the 76 bikes.  The 76 bikes did not use the speed sensor and circuit card - the solenoid was fed from the change switch itself.

http://forums.sohc4.net/index.php?topic=112231.0

And yes - I test solenoids using a 9V battery - it will operate at 9V.

[shortbloke]

many thanks for that. I looked at the speed sensor it seems to be the last port of call. Are they the same as a gl1000 they are more readily available and a whole lot cheaper.

[raymond10078]

I am not aware that the GL1000 has a speed sensor.  When I say speed sensor, I'm talking about a device inside the A speedometer.  I just reviewed the GL1000 schematic, and it differs from the A speedo.

Maybe it will help to understand what the speed sensor does.  As you know - when you at a stand still, and put the bike in gear, the solenoid is energized, and the carb throttle is opened slightly so that the idle speed doesn't drop.  For the 76 A bikes, the throttle is held open this slight amount anytime the bike is in gear - at all speeds.  For the 77/78 A bikes, Honda changed the design so that the idle control shuts off at a certain speed (17 MPH, I think).

The reason for this change in design - no one knows (or if they do know, they haven't fessed up).  I thought that maybe it could be for "engine braking" - or it could be for emissions.  Either way, the 77/78 A function - we certainly don't NEED it - but we may want the bike to operate the way it was designed.

I only share all of this as justification for reverting back to the 76 design.