Topic: Electronic ignition advance.

[cafehonda]

Any idea on how far one can adjust an electronic ignition plate to advance spark with out doing damage. I have a Martek 440 on my '73 cb750. I have advanced spark @ 2 degrees (rotating plate counterclockwise) without any signs of detonation. I do burn 100 octane low lead exclusively. Also, on the same topic, has anyone tried any of the adjustable ignition systems such as Dyna 2000? I would assume one would need a dyno with an exhaust gas analyzer to determine appropriate curves.

[Bodi]

Check the timing at full advance only, the "F" mark only tells you the idle timing. If you advance it too far you'll get preignition and knock but this is really hard to hear on an aircooled bike with highway wind in your ears, and it only happens at high throttle and mid-high RPM. Unfortunately it can melt your piston crowns fairly quickly though.
Two degrees is a mild advance. Using high octane gas you should be able to go further safely, it's just hard to know when you've gone too far.

[TwoTired]

Bodi's response is spot on as usual, and saved me a lot of typing, Thanks Bodi!

The only thing I might add is that there is some interaction between mixture ratios and preignition/detonation.  A rich mixture has a cooling effect, delaying onset of preignition, as will higher octane fuel.

Do a plug chop to see how your mixture is now under power and engine load.  The darker the insulators are, the more tolerant of timing advance experiments the engine will be.

Another factor would be the heat range of the spark plug.  A colder plug will wick heat away from the chamber, also delaying preignition/ detonation.

Finally, if you are going run on the raggedy edge near preignition, don't ignore temperature and barometric pressure changes from weather or altitude.  Ma Nature will change your mixture ratios for you on any given day/place.

Cheers,

[doug_id]

Doing the search thing and came across this thread.

Trying to nail down the timing on my newly installed dyna-s.  Seems when I have idle set correctly the advance marks are too far forward of the mark.   How can you adjust the advance without affecting idle.....or should I just ignore the idle and get the advance nailed down?

Thx,
Doug

[TwoTired]

Doug,
You set the timimg to where it is supposed to be.  F mark near idle.   And then use the big knob on the carbs to adjust idle when fully warmed up.

Cheers,

[crazypj]

Have you checked advancer mechanism for wear? the bobweights and stop plates both allow excess advance over time as they wear away.
 Its not usually more than a couple of degrees but I have had to weld up plates to prevent over advancing on modified motors ( a lazer welder would be overkill for that, but really really neat ) As you can tell, I'm impressed with that machine
PJ

[MRieck]

 The newest Dyna 2000's are programable which allows you to build your own advance curve. Nice

[doug_id]

Doug,
You set the timimg to where it is supposed to be.  F mark near idle.   And then use the big knob on the carbs to adjust idle when fully warmed up.

Cheers,

Hi TT,

Here is my process for setting the timing with the dyna S.   

1.  set idle to between 1000 - 1250 rpm
2.  Attach timing light to #4 plug wire
3.  Shine light in peephole and verify that mark above the F is line up with reference mark.  (initially it was to the left of mark so rotated dyna s to the right until it lined up)
4.  Do the same with plug #3 wire (it was ok at idle so no adjustment)
5.  Using idle adjustment screw raise idle to 2500rpm
6.  Attach timing light to plug wire #4 and inspect advance marks.   The advance marks a fair amount to the right of the reference mark.

So, not seeing how I can get both the F mark at idle and the advance marks at higher rpm to be correct.  If I set for one the other will be off and vice versa.  Been reading old posts and it sounds like getting the advance marks aligned correctly is more important?

With the original points plate all the settings for idle and advance were spot on so not sure why the difference with the dyna s 

Thx,
Doug

[doug_id]

Have you checked advancer mechanism for wear? the bobweights and stop plates both allow excess advance over time as they wear away.
 Its not usually more than a couple of degrees but I have had to weld up plates to prevent over advancing on modified motors ( a lazer welder would be overkill for that, but really really neat ) As you can tell, I'm impressed with that machine
PJ

hmmm not sure.  With original plate both idle and advance marks were right on.   

I will get out my laser welder and take care of it.   

[doug_id]

The newest Dyna 2000's are programable which allows you to build your own advance curve. Nice

Yea, I have seen those on Z1.......I could really screw things up good with that capability.....doh!   

Doug

[mlinder]

Hey Doug,

I just installed a dyna s. You did set static timing to the advance mark, yes?

[doug_id]

Hi ML,

No, I didn't do the static method.  I had a timing light so went that route.  The instructions said either should work?

I didn't have to much time to play with it last night....it was getting late and the bike is loud so didn't want to piss of the neighbors to much 

Will give it another try this afternoon.

Doug

[mlinder]

Set static timing on the advance mark. See if it helps.

[doug_id]

Have you checked advancer mechanism for wear? the bobweights and stop plates both allow excess advance over time as they wear away.
 Its not usually more than a couple of degrees but I have had to weld up plates to prevent over advancing on modified motors ( a lazer welder would be overkill for that, but really really neat ) As you can tell, I'm impressed with that machine
PJ

Got to reading more on troubleshooting the dyna s.  Says to twist the dyna s rotor to open the springs on the advancer mechanism then says to let go and the springs/rotor should snap back into closed(?) position.  Mine do close but I wouldn't call it a snap motion......seems kind of slow to me but I don't know how fast they should close.   Could that be the issue?   When I have the timing set correctly for the advance marks at 2500 rpm.  The F mark at idle is a ways to the left of the reference mark.

Thx,
Doug