Topic: 1975 cb750F no power to starter - neutral switch?

[macvit7906]

Hi All,

This question is for the wiring experts and/or anyone who owns a 1975 CB750F. I searched around the forum and cant find a specific answer.

I'm getting around to doing a first start on a complete restoration of this bike. Motor has been completely rebuild.

New battery, wiring harness, and starter solenoid. Start button has been rebuilt and bench tested good.

When I turn the key on power, i get no neutral light, even though the bike is in neutral - the bulbs in the dash all work and have been tested. I get an oil pressure light as expected.

When I hit the start button, there is no power to engage the starter solenoid. the 75' F1 does not have the safety unit in the electrical tray. It has the diode (tested for current one way not the other).

I had reused the old neutral switch - it's possible its broken?
Would a broken neutral switch not allow power to the solenoid?
I do not have the clutch safety switch (waiting on it from 4into1) - but figured I could still start the bike in neutral

 

[kerryb]

From the wiring diagram on this site, it appears you could ground the wire going to the neutral switch (be sure it is in neutral ) to see if there is power to the solenoid.
Is it possible to put the diode in backwards?
You could also put a jumper wire on the clutch switch leads to simulate the clutch being pulled in.

[macvit7906]

From the wiring diagram on this site, it appears you could ground the wire going to the neutral switch (be sure it is in neutral ) to see if there is power to the solenoid.
Is it possible to put the diode in backwards?
You could also put a jumper wire on the clutch switch leads to simulate the clutch being pulled in.

Thanks Kerry. So essentially it is possible that a fault neutral switch would not allow power to the starter.

It's not possible to install the diode backwards because there is a horizontal pin and a vertical pin, can only be installed one way

[bryanj]

There should be a switch operated by the clutch lever so the engine will start EITHER with the light on OR the clutch lever pulled in

[scottly]

New battery, wiring harness, and starter solenoid. Start button has been rebuilt and bench tested good.

When I turn the key on power, i get no neutral light, even though the bike is in neutral - the bulbs in the dash all work and have been tested. I get an oil pressure light as expected.

When I hit the start button, there is no power to engage the starter solenoid. the 75' F1 does not have the safety unit in the electrical tray. It has the diode (tested for current one way not the other).

I had reused the old neutral switch - it's possible its broken?

Use a jumper wire with alligator clips to connect the green wire where it connects to the neutral switch, to ground. If the switch is at fault, the neutral lamp should now light up. If it doesn't light, you have a wiring problem, and can rule out the switch.

[macvit7906]

Thanks All,

It was the neutral switch.  I now get power to the starter and a neutral light!