can I use a 12V car battery to start/idle bike ?

[suzukiSam]

I acquired a 1980 GS1100, but it didn't have a battery - I want to see if the
bike even starts, but I don't really want to drop $75 for a bike battery only to find out it doesn't run.

Can I "safely" (safe to me, safe to the battery, safe to the bike's electrical components) use a car battery to start, and idle the bike ?

If and when the bike starts and idles, can I disconnect the battery or will it stall out ?

[Nicholaschase29]

Yep.......... just dont start the car while its battery is connected to your bike

[bonanzadave]

Just having the battery sitting beside the bike (not hooked up in a car) with some jumper wires should be ok.

When was the last time this bike ran ? Does it turn over ?

[suzukiSam]

the sticker on the plates indicate 1999, so it might not have been run since the year 2000 (8 years)..

I've sprayed some light grade oil into each cylinder, and drained/replaced the engine oil that was in it, and I'm going to manually try to turn the crank before I try to start it 'electrically' (with plugs removed). Anything else I should do ?

And I'm not sure I've found 'neutral' yet as the rear wheel doesn't turn freely until I pull the clutch lever in.. 5+ kicks down, and half up on the gear changer should be neutral ?

[gpans]

And I'm not sure I've found 'neutral' yet as the rear wheel doesn't turn freely until I pull the clutch lever in.. 5+ kicks down, and half up on the gear changer should be neutral ?

I think you have got it right, but don't get frustrated if you can't find neutral right way. Shift as much as you can downward then when you can't click down anymore, tap your foot upward until it feels like it has settled slightly but it hasn't clicked. When you try kickstarting it (slowly at first), you have found neutral if they rear wheel doesn't move along with it. While testing this it might be wise to have someone nearby holding the bike in case you have accidentally engaged your gears-your bike could jump off its stand and tip.

[doctorgonzo]

Others have answered on the car battery. I'll just throw in you can get a bike battery at Walmart for more like 45 bucks not 75.

[JayH]

Dont' keep cranking the engine if it doesn't start right away. The car battery will put out enough juice to crank the starter but the starter gets HOT very quickly.

[nisom512]

Dont' keep cranking the engine if it doesn't start right away. The car battery will put out enough juice to crank the starter but the starter gets HOT very quickly.

well wish I would have known that.....

[spyug]

Welcome fellow Ontarian.

If you're doing the testing with the bike on its centerstand, run a stout rope or tie down around and through the stand and tie through the front wheel. It ensures the bike stays up if it is in gear and the back wheel grabs. Its also a very good idea to have a helper steady things and put a bit of weight on the front end.

Do everything you mention especially turning over by hand.

Trying to get the bike to fire can be a royal pain and you might need a bit of joy juice to encourage it. I'd also invest in fresh plugs. If you can take off the airbox you can access the carb throats and spray in a little bit of gas.......never ether or Crappy Tire starter fluid as too much and you can blow off the head. Use an old spray bottle ( Windex or the like)These bikes don't like to run lean so you might find it coughs and farts but won't run until the filter and airbox are back on. If there is signs of life button things back up and try again.
As mentioned just don't crank it continually, let it rest for 5 or 10 minutes after each attempt.

Keep us updated and send pics.

Cheers and good luck,
Spyug.