550 got some loving today!

[Lifttech81]

Had a productive day with the old girl. Fresh oil and filter change.
Got some shine into a few chrome pieces I could get to. First time I've looked at the rear tire alignment/chain tension since I got it. Spec for chain lash is 20 to 30 mm. Mine was about double that. Tire was also out of alignment. All in all pretty mint. Aligned it and got the correct tension on chain and away we were for a test drive!

Ride went super smooth, she ran great. Parked in my driveway and attempted to duplicate my intermittent no start when hot. Wouldn't fire with the ignition switch. Cranked for days all lights working and fuel getting to carbs. Decided to try and push start it. Pointed downhill popped the clutch in first and fired right up. Getting the meter out tomorrow and going to start testing/inspecting the starter and ignition circuit. Anyway enough of that! Pictures

[Big T]

Time for the Quick Test. Voltage at battery
Key on
Starter button pushed
Running at idle
Running at 4k rpm

[Lifttech81]

I like it, will report back with values

[Steve]

The emphasis on your voltage testing will be when the starter button is pushed and the starter is working.

It <should> remain comfortably over 11 volts with a good battery. If it drops below 10, there is a good chance there isn't enough 'juice' left to fire the plugs.

On larger engines, there is a bit more inertia in the crank assembly. There are times when the battery is just starting to get weak enough to fire the plugs, but when you remove your thumb off the starter button, there is still enough motion in the crank to fire the plugs and away it goes.

.

[Lifttech81]

Makes sense. I did top of the distilled water and let it trickle charge overnight when I first got it. We'll get the fluke on it tomorrow

[Big T]

Common issues are weak battery and starter drawing too much current ad it's gummed up

[Lifttech81]

If I get any low values tomorrow I'll take the battery out and do a bench load test on it. Probably end up going through starter and all connections too. Pictures and info to come !

[Lifttech81]

For some reason I always find bikes with no kick start go figure

[Lifttech81]

Got all my values this morning

Key off battery voltage 13.4
Key on battery voltage 12.9
Key on headlights on 10.6
Key on cranking. <10 volts and dropping fast

Going to grab a new battery today. As soon as I turned the headlights on the voltage dropped too low to fire the coils and wouldn't start. Turned the headlights off and checked and started up fine. Once running voltage hovers around 13.5. Also going to check all grounds and connections for starting system/ignition.

Put the battery on the bench load tester and immediately failed

[rphillips]

You shouldn't be able to turn the headlight on/off on an "81" model. You're not doing something illegal are you??? I'm sure nobody around here would install an illegal headlight switch on a GS.

[Rich82GS750TZ]

You shouldn't be able to turn the headlight on/off on an "81" model. You're not doing something illegal are you??? I'm sure nobody around here would install an illegal headlight switch on a GS.

I wondered the same about the headlight on/off switch on an '81

[Lifttech81]

The biggest switch to on the top right of left handlebar switch is the main lights on off switch. Looks quite factory to me

[Lifttech81]

Looks factory to me. Even has testing procedures in the manual.

[Lifttech81]

Believe it could be touring model specific

[Rich82GS750TZ]

I'm fuzzy on the specifics, but believe that (at least US model) motorcycles were equipped from the factory since ?'78 with a non-operable on/off switch. Meaning you can't turn it off without modifying the innards of the switch mechanism. That's why it seems odd that you would have a functioning factory headlamp on/off switch on a /81. Maybe someone else can either clarify or debunk my statement.