Starting issue in cold weather
 

I noticed lately that my 1990 xt600 is hard starting in the cold weather in the morning around 30 degrees. During the day no problem. It seems like after a revolution as she cranks then she starts to grind. If I leAve it on a battar y maintained over nite she starts ok. This is the first year I leave her outside for now usually I keep her in the garage. Any help would be appreciated thanks

Sounds like a battery getting towards the end of its life to me. How old is it? Cranking 600 singles over is a tough call on batteries and more so in cold weather with thick oil etc.

Tired battery. You could test it--Google will find lots of descriptions of how to do this. You could just replace it without testing, then wonder why you waited so long. You could make a point of plugging it in overnight, night after night, thereby stretching things out until the weather gets really cold. Or you could run through all the possible causes, including various cables and connectors, water levels, voltage and current measurements, etc. etc. etc....and then replace it. Probably.

Just changed the oil to a lighter grade also will change battery. Connections are good What battery are good. I go on Amazon some are ones I never heard of and auto zone are more then a car battery I don't remember how old this one is but it's a Yusca that I bought from the dealer

Yeah I remember somebody saying that here. I would just buy one but...don't want to be just a parts changer. Never had this issue until outside. She is a daily driver until first snow storm then away she goes for 3 months or a little fun just to get her warmed up

Best like for like battery I've ever used in a bike is an Odyssey, but they're expensive (!) and may not be an exact fit (you have to choose the nearest that'll go in the battery box). On the up side though they crank better and more reliably than anything else I've tried and last much longer (I have one that's 10yrs old and going strong).

I know what you mean about being a 'parts changer' so it might be good to check the charging side of the bike is doing its thing. The quick and dirty way to do that is to point the bike headlight at a wall on tickover and slowly raise the revs to around 2500. You should see the headlight get slightly brighter as the revs rise. It won't be much as the reg kicks in to stabiise it but if it does brighten it's likely the bike is charging ok. If it's not obvious then the next step is a multimeter. Having to use a charger overnight though is the clue it's the battery. I had to do the same thing with my Land Rover a few winters ago. A new battery fixed it.

A little helper juice
 

I ran a small plastic tube from the air cleaner to just below the gas tank to flow a shot of WD-40 or carb cleaner into the intake before the carb in cold weather. The engine likes this little shot of helper juice -fires right up. Like OP noted, after the engine is warm the stock battery does the job. No difference was noted when I changed oil viscosity.