G'day Fellas.
1988 FXST basically stock only 26K on the clock. Newish AGM fully charged.
Before I start pulling it down I thought I'd better ask ???'s here.
After a days riding it was getting dark so turned the headlight on. After 5 or so miles the motor started to miss. Turning the headlight off it came good. Tried again and same result. Still had 30 miles to go so waited for a car and followed him (country back roads).
Today on a short ride even just using the indicators produced a slight miss.
Any ideas where I should start looking. I can rebuild a motor/gearbox in my sleep BUT show me a wire and I run LOL.
Cheers

 

Time to check the charging system.. there's a sticky at the top of this forum.. Start there and get a Factory Service Manual..

 

Try tighten the connections at the battery. Do you have a vote ohm meter?

 

Thanks fellas.
Did a little testing in the shed. At stand still battery at 13.3, ignition on 13.2, on starter button 12.6, at idle 13.5, at revs 14.5. As soon as I turn headlight on the charging rate stays the same but the motor falters. Turn lights off and motor clears.
Discount the short ride today, the carb was flooding!
GMF'd. I'm suspecting the ignition switch.
Cheers

 

Sounds like the switch.. Just a couple of weeks ago another forum member had identical issue.. Said the switch cured it...

 

In addition to checking the connection at the battery, check your battery to frame, and frame to engine ground wires/cables.

Also check (because your there) your voltage regulator to frame ground, some voltage regulators have a dedicated ground wire that goes from voltage regulator to engine/frame mount, others just use the mounting bolts, but it has to have a good ground.

 

Yes, sounds like the charging system is working.

Check the grounds. Also, put the + lead on the coil positive, - lead on the battery negative. Start the bike. What's the voltage? Turn your lights on. What's the voltage?

What you describe could be a bad connection in the ignition switch or possibly a bad main circuit breaker, besides a ground. Those are about the only common points in the 2 circuits (lights and ignition) I can think of.

Note that the bike came with the switch wired: Off, On (all, ignition and lights,) On (all, ignition and lights.) If you can turn the lights off at one position, someone removed the jumper wire. Putting the wire back will probably fix your problem for cheap if it's the switch. Just don't use the "lights" position.

 

Thanks again Fellas.
Will go through all those checks in the morning.
Having a few drinks now, my team just one their semi final. Go South Sydney Rabbitohs.
Cheers

 

That 13.2 at stand is residual from charging. Always after turning of, hit light to kill that. Then check. Should be 12.6 or so. All else looks good. That cranking volts is high compared to a TC. Mine is like 9.9 at most.

 

G'day Fellas.
A little more testing.At rest 12.8, H/L on motor off 12.2, cranking 10.3, at idle 13.5, at revs 14.5, idle H/L on 13.5, at revs H/L on 14.5.
Voltage at coil at rest 12.2, at idle 13.1, at revs 13.1. With H/L on at idle 11.5, at revs 12.0.
I disconnected the lights wire at B on the ignition switch and problem disappeared, touched wire back on B and it faltered!
I also made up an extra earth lead and touching it on the motor or frame made no difference.
Could it be the H/L relay?
Cheers