1984 Yamaha XJ 650 wont stay running

Yes i ned it

Sounds like a badly bent shift fork. Parts will be hard to find. Finding a dealer willing to work on a 30 year old bike will be even harder. The cost to repair would be around $1250. That is more than the bike is worth. I don't advise you to attempt the repair yourself. Some special tools are needed and you would be doing major surgery on the transmission.

What you are saying is the engine runs when there is a good supply of petrol by top feeding the carbs but not when fed from the tank.
That suggests the supply from the tank is restricted in some way.

The cv carb slides wont lift until there is air flow flowing through the carb ie engine running.

2 things need to be done first start your bike get a can of wd40 after your bike is warm and running spray around the carb jointsall 4 of them if your engine changes rpms up or down you have a intake leak ether your carb joint gaskets or o-rings need replacing or your carb joints are old and need replacing. at this point wont hurt to have you carbs cleaned also

Your regulator/rectifier is shot, replace with new one also new battery as that will most likely be shot to.

not enough to go on, but these were not slow bikes. try plugs, mucky carbs, carb jets, air filter.... take out plugs, any dirty black while others are clean or white? start bike from cold, run very short while and turn off. carefully feel exhaust pipes at top, are thay all same temp? one or two not getting warm? watch you don't burn your hands....will tell you if all cyliders firing ok.

you will never have gas coming from the shifter, gas only goes from the tank to the carbs then as a vapor into the cylinder for combustion. if it is gas on your shifter then it is dripping from somewhere or maybe your carb overflow tube which will exit under the bike at rear of engine. if this is the case then you have a sticky float in the carbs. turn off fuel tap and it should stop. but if you are in the USA get some Berrymans B12 fuel additive and double the dosage and run bike til hot then leave to stand overnight. this should break down any gum/varnish which is making the floats stick. if it don't then run it again and do the same. if all else fails you will have to remove carbs and take off the float chamber bowls and clean them with carb cleaner

I have the same bike. The shocks on the rear have adjustable preload which can lower the bike for you. Or you may even be able to find shorter shocks. Check this site for great info on these bikes. www.xjbikes.com