Headlight flickering, engine stuttering at speed

[FreddieF]

Hi all,
I've had my 84 Heritage Special for a couple of months and it had been running OK until last weekend when it suddenly started hesitating at highway speed during a long ride. Now it does it after a few minutes of riding. Low speed and idling don't show the problem.

The carbs have been out a few times and everything cleaned - everything is stock. Compression test is OK, cam chain adjusted, valve clearances are good, carbs are synced, no air leaks (unlit propane torch tested). Still no joy. The stuttering seems to get a bit better switching to PRI - but not much better - vacuum? Unrelated?

Last night I went for another test ride and noticed the headlight flickering a bit now and then - aha, inconsistent spark or something. Brushes are just at the point of replacement 7mm - would that cause the problems listed above??

And just how do you reinstall the brushes? Seems you have to turn the brackets upside down and have the wire go around it??? That's strange or I'm doing it wrong.
Thanks for the help!

[Chuckwagon]

Have you checked that the battery ground is in good condition and bolts are tight?

[xsleo]

Yes, the symptoms you list sound like a weak charging system.
The brushes can be a bit of a PIA. The wire and the fiber piece get wrapped around the metal to fit in the holder. Be sure the fiber piece fits into the holder right before you tighten the screw fully.
Leo

[FreddieF]

The battery is only a month old as is the coil, wires, plug caps and plugs. It is securely fastened to the frame. The battery reads 12.5 when bike is off, 13 or better when idling and 14 or so when revved to 2500. These numbers fall into the spec - don't they?
The headlight flickering maybe a bit of a misnomer - it dimmed slightly for a second, them back up to full intensity while the engine coughed. That was a few nights ago. When I had the brushes out just to see what's what, one of them was angled a wee bit so I lightly sanded both and reinserted them. Last night I did not notice any dimming or stuttering at all, nor today???
All I did besides the brushes was to put in a spacer to let some air inside the little cover (a la xsjohn). New brushes are coming tomorrow. Can the brushes being at the limit of wear have caused this? I can't wait to see tomorrow!
Thanks for your help!

[xsleo]

The book says the brushes can wear to 1/4 inch long. They can start giving trouble at 3/8 inch. New brushes won't hurt. The sanding you did cleaned off the brush and allowed better contact between the brush and rotors slip rings. This improved the the alternator output a bit. If you want, pulling the stator and cleaning the slip rings is a good idea. It can be done with the stator in place, just easier with it out of the way. I ue 400 or 600 grit sand paper then spray down with electrical contact cleaner to remove any traces of the sandpaper.
Going through the wiring and cleaning all the connectors, squeezing the female parts a bit tighter, adding a bit of dialectric grease helps keep them clean. the switches can be cleaned too if you feel brave.
Leo
The spacers will keep the rotor and stator cooler. Cooler is better.