G1 spark problems

[lady bug]

HI I just purchased a 1980 yamaha g1. For some reason it runs fine in foward but will not fire in reverse. I pulled the plug and fires fine in foward but will not fire in reverse?

[Prowlerguy1]

I would suspect that some contacts in the key switch are the problem.

See the attached drawing.

When the key is turned to the REV position, the connections highlighted in yellow in the chart above the key switch are "connected."

In the REV direction, you can see that power is sent to all of the wires that are highlighted in red.

I would be most suspect of the W/R wire going to the CDI Magneto and CDI Unit.

With the key in the FWD direction, power is sent to the CDI Magneto and CDI Unit on the W/G wire - so we know that works. But, in the REV position, power is not getting to those items....somehow.

Check the W/R wire with a voltmeter with the key on and see if you're getting 12V. If not, it's probably the key switch that is the problem.

If you do get 12V on the W/R wire, next check all the connectors between the key switch and the CDI components.

Good Luck,
Todd

[lady bug]

Thanks much for the reply. It was very helpful found that the culprit was a brocken green white wire in the harness

[Prowlerguy1]

Looks like I was almost right!

In the original wiring diagram from Cunningham site, there are actually 2 columns labeled with the W/G wire. I took a shot and figured that the one on the same connector with the Red wire was the W/R wire and that it was for the REV function. I had a 50/50 shot!

I will re-label the columns correctly. The W/G apparently powers the REV and the W/R powers the FWD system.

Glad you found the problem.

R/Todd

[lady bug]

Thanks very much for taking the time to look into it and help me out.