Mechanical Ignition Advance

[tobaccorancher]

Hi, I have a 1979 GS750, and am still running on breaker points. I was experiencing some back-firing during acceleration and decided to look at the ignition system to see what might be wrong.

I put in new points, set them, and did the static timing without issue. The bike starts better now than it did before. But, I am still getting the backfiring on higher rpm. So, I put a timing light on it. The timing is perfect at idle, but when I bump the throttle it essentially does not advance at all.

So, I took the plate off to get the the timing advance thingy. Not sure what it is called, but I it has the two springs, and looks good. I am able to push either arm to simulate centrifugal force and the arms move and the timing cam advances.

Has anybody run into this before? Could it have been an installation issue, something binding that I have released by taking it apart? Or, are my springs so weak that they are "advanced" all the time? I do note that I can push the arms of the advance mechanism out with very little force.

I guess I could go all electronic, but I really want to keep this bike period correct if I can.

Thanks,
Andy

[Nessism]

Can you grab the cam and twist it? Then release, and it springs back?

[tobaccorancher]

Yes, thanks for responding. When I took the plate off I was able to move the arms with a screwdriver and the cam advanced. I took it apart today and cleaned and lubricated it. When I had it out I thought that maybe the timing cam was installed backwards so when I put it back together I put it in the opposite way. Then, this evening I could no longer get the bike to start, so now I know that it was installed correctly before I took it out. So, put it back the right way but ran out of daylight. I'm not sure why I was not getting any advance....the advance mechanism seems to be fine, but when it was installed for some reason it was not giving me any advance.