Topic: No spark at plugs when cranked, but spark when snapping points.

[bahia]

Very curious situation. '73 CB500, but with a 550 wiring harness.

At one point I had the bike running with a jumper from a car battery
(positive going directly to black/white lead to coils & hit the starter lead,
ground secured to frame)
Now, I can't even do that.

I don't think anything I've done took the points out of the original timing (nothing rotates when I grab and twist by hand).

When I snap the points with a screwdriver, I see spark at the plug. But when I combine black/white lead, battery pos, and starter, I get nothing.

Any thoughts?

[754]

Try switching coil leads , might be tying to fire 180 degrees  out.

[Spanner 1]

Crappy battery. It's got enough juice to fire the plugs when you slap them open and shut, but the starter takes all the energy and nothing left over to power the coils = no spark when trying to start the bike . Actually, even with a good battery unless the points are shiny clean, the same may result .

[scottly]

Not sure what you mean by "snap the points with a screwdriver"? When the points are closed, the coils charge up, and when the points open is when the spark happens. Are the points actually opening and closing properly when the motor rotates? The point gap at it's maximum should be between .012-.016 inch.

[bahia]

@scottly, I'm manipulating the points with a screwdriver. When I snap one side open, I see spark on the plug (pulled and grounded).
The points are moving, but not sure if the gaps are correct. My next step is to purchase a feeler gauge and set the gaps per static timing.
But even still, pretty sure nothing's changed with the points between the first time I had it running and now.

@Spanner 1, I'm running leads from my truck's battery (bike didn't come with one, and haven't ordered one yet). It's possible I have just under 12v.

@754, Worth a shot at this point.

[PeWe]

Can be as mentioned, points gap too wide, not closing. I have done that too

[754]

 Scotty , I don't use a meter. SO FIRST CHECK for spark Is open a closed set of points, they should spark and fire the plugs...which you may hear plug clicking. .
 Not always good to do indoors, as it can backfire. I had one backfire in a 3 sides open carport, that just about made me fall off the chair

[bahia]

Spanner pretty much got it in this case.
Yesterday I was jumping from my trucks battery (while not running), and it was probably under 12v.
With the Xterra running I had 14v. Tried it this time, and was good to go.

Confirmed I can jump the yellow/red and green/red to start as well.

So now get the correct start switch (the CB500 only had the yellow/red wire), and work on everything else I need to get this thing on the street.

Thanks for the advice!