Topic: pamco and timing mark? any help would be great.

[mario medeiros]

Have a 72 cb750 that I did a major rebuild on and installed a pamco ign on it (basic unit) and the bike would not start.Revesd the coil wires and she started right up and ran well.put the timing gun on it on #4 wire and at idel got it to the f mark no problem,then tried to time it to the advance mark and it was way off,and now the f mark at idel is off.At idel the marks seem to be near the advance marks.Bike run's great and I even took it for a short ride,no flat spots or back fires just runs great.Any idea on why I can not get my marks right?Could it be because I swapped the wires going from the pamco to the coils? Could it be a old #$%*ting timing gun?I did remove the advance before installing the pamco and took it all apart to clean and lube and also to grind down the pin.Thanks

[AJK]

I would say that assuming your advancer travel is working correctly. I.e. It can correctly advance between the 'F' mark and the || marks as you rev the bike up, then that will verify that your advancer is operating correctly.

Then after checking that, just keep the bike reved to say about 4000 rpms, and set the timing to the || mark. Then when you allow it to idle, it will land somewhere around the 'F'. Just let it land where it wants to and you will be right.

Some other threads that may interest you are:
http://forums.sohc4.net/index.php?topic=113480.0;all

and

http://forums.sohc4.net/index.php?topic=122946.0

[pamcopete]

Mario,

The ignition system is a wasted spark system, and one of each coil wires is a positive voltage while the other is negative. The timing light works best on the negative wire, but there is no easy way to determine which one that is, so just try connecting your timing light to the other wire. IE: Try using #1 cylinder instead of #4.

Also, if you are using a timing light that has built in advance settings, they do now always work reliably with a four cylinder motorcycle engine, so just set the timing light advance to zero.

Also, make sure that the PAMCO rotor returns to its resting position if you rotate it and release it so the springs will pull it back to its resting position.

[mario medeiros]

Thanks guys,i will try that out (move over to #1) it just bugs me that at 1st i was able to dial in the f mark no problem but the advance was off and once i turned it off i restarted the bike again and tried to time it and now i can not even see the f mark at idel? but i must say the bike runs real nice,lots of nuts ,no back fire ect.

[pamcopete]

Thanks guys,i will try that out (move over to #1) it just bugs me that at 1st i was able to dial in the f mark no problem but the advance was off and once i turned it off i restarted the bike again and tried to time it and now i can not even see the f mark at idel? but i must say the bike runs real nice,lots of nuts ,no back fire ect.

You could also try a different timing light. Maybe borrow one from a friend or rent one or buy a new one for about $40.

[PeWe]

Advancer unit springs probably too sloppy. Full advance will be reached way too soon, spittting carbs, right?
I had that problem solved by tightening both springs. Cut each 1/2 turn and reshape them.
http://forums.sohc4.net/index.php?topic=131339.0

My theory about it is that the points have a counter force against the cam that the advancer unit move. This is removed when using an electronic system. The rotor spins freely reaching full advance too easy with no points acting as extra springs. The advancer springs must be tightened to compensate.

Dyna ignition instruction just do it simple by setting the timing OK for full advance marks ' ' at 2500rpm. Idle setting not important here. This is one way of avoid the ignition setting at idle.
Tightened springs will allow OK timing at idle AND full advance at 2500-2900 rpm.

I made this setting for Pamco ignition, changed later to Dyna when the Ultimate coil had bad wire attachment that were loose causing difficult carb jetting and finally blew the ignition.

Now Dyna S system in and finally possible to drive the bike for fine tuning. Play in the advancer unit, make everything more complicated. I have tightened the unit at max clockwise position delaying everything and marks not to be trusted.
I'll set the timing until I hear pinging when twisting the throttle at 100-120km/h on 5:th gear. Then retard a little.
- Finding exact TDC and update the marks is the correct procedure -