Bad Condenser??

Okay...
So 1977 R100S, last week it started coughing and sputtering at speed..
Naturally I assumed it was time for a spring-time carb clean-out..
But squeaky clean carbs didn't correct the problem.. checked the air filter, valves.. nothing.

Then I remembered the adage I've seen posted here about the majority of carb problems being electrical.....

So popped off the front cover to check the points- when I run the motor watching the points, at about 3500-4000 rpm's the small spark you see on the points grew to what looked like a spiderweb of electricity covering the whole points area...... and (shocker!) when the arcing grew to that degree is when the motor would sputter....

So, bad condenser??

You replace condensor every time you replace points, right? And now these points are ruined by the arcing. So, you'll be able to observe with the new parts and determine if you've solved the problem.

Well actually the points and the condenser I've got now are *pretty* new... under two years old....
Will the arcing destroy the points? (Even if I've only driven ~15 miles since the issue cropped up.....)

Could be a bad condenser, but also just the advance weights hitting the lead to the points as they spin out for advancement. I have seen it more than once and the symptoms are the same as yours, sparks fly as they hit the wire. Check the clearance as the weights are moved out, it is usually the end where the lead attaches to the points that hits the advance lead. On a separate note, most condensers that I have seen fail usually fail to the "shorted" condition, meaning they actually ground the voltage and the engine does not run at all. If it would fail "open", the points would still work, but as you noted, have a short life. An inspection to see if they are badly pitted is the only way to tell if they are any good. You will be surprised at how badly pitted they can be and the engine still run ok.

Better answer;

DYNA3 if they are still around. Mine '78 R100 has been without points for decades and SOOOOO much better for it. Points are OK if you're into suffering. Burned myself too many times working on points, finally learned about 5 years into this bike around 1983 or so, threw them points away. Yep, they(points) are easier to fix in a roadside emergency, as OLD answer always pops up in this. Never had a electronic ignition fail, going back to points for an answer. Randy

toooldtocare said:

sparks fly as they hit the wire.

Click to expand...

Now do you mean sparks as in just "metal hitting metal" sparks? Or electrical sparks?
What was going on was it electricity arcing all over the place-- I would see just the small arcing/sparks around the points, and then as the throttle increased, the arcing would spread to all over the points...

As the weights spin they touch the wire shorting out the points creating electrical sparks. Looks just like you described. Check the routing of the wire, push it down and ensure the end does not touch the weights. Just barely touching will create a lot of electrical sparks at 3k rpm. This problem is common. Edit: Also make sure the advance unit is tight.

Wayne

Nice call Wayne- that's what was going on.. the wire was in the way of the weights...

But, I'm thinking I must of shifted the wire when I removed the cover... doh!
So my gremlin is still on the loose somewhere else in the bike... back at it....!

Glad one problem is fixed, but before you start tearing into it more, ride the bike and see what happens. I have seen this happen as the bike gets warm with new points, the jacket on the wire gets soft as it gets hot and allows the wire to take a new position, sometimes hitting the weights. If it is not this, well there are lots of things to check.

I sold my Motorsport last year, but it had a gremlin in it that I never could find. It had a Dyna III, dual plugs, and a bunch of other hop up goodies like a hotter cam, lightened wrist pins, etc. Everything had been gone through several times, but every once in awhile it would cut out at round 3k on one side, just like it was running out of gas. A second later, it would light off just fine and may run for hundreds of miles before it would do it again. I never could find the bug and replaced a bunch of parts looking for it, including rewiring the Dyna system, new plug wires, plugs, rebuilding the carbs, etc.

Good luck.

Wayne

toooldtocare said:

It had a Dyna III, dual plugs, and a bunch of other hop up goodies like a hotter cam, lightened wrist pins, etc. Everything had been gone through several times, but every once in awhile it would cut out at round 3k on one side, just like it was running out of gas. A second later, it would light off just fine and may run for hundreds of miles before it would do it again. I never could find the bug and replaced a bunch of parts looking for it, including rewiring the Dyna system, new plug wires, plugs, rebuilding the carbs, etc.

Click to expand...

I had a similar "annoyance" with my /7, also with a Dyna III. My cutouts never lasted a second, but more like momentary hiccups. Never could figure it out, but I didn't pursue it all that much. A few years later, I had a temporary failure of one side while on a trip...used the Anonymous to get me going again. A few more years down the road, the one side failed again. I replaced the Dyna III and have been trouble free since. My thinking is/was that some corrosion was getting behind the sensor plate and occasionally, the loss of ground caused the system to run poorly.