Triumph Adventurer Problem In Starting

Welcome to the forum! It's best to start with the really simple things since the bike has been sitting for a while. You might want to drain the gas and replace it with fresh gas - or at least put an octane enhancer in it. Also, you say the battery is good, but don't say how you know. Have you checked to see if it has 12.6+ volts? If it doesn't, then try charging it overnight and see if it maintains that voltage. If these suggestions, don't solve your problem, send back as much detail as you can, and I'm sure you'll get some help from the forum members.

 

make sure your battery is in top condition because a low battery can cause a failure of the sprag (starter) clutch which is an expensive job.
apart from that the above advice is good, I would give the ht leads a spray of wd40 in case of damp too. if you have kept trying to fire it up you may have flooded or fouled the plugs. try with or without choke, my Sprint doesnt need much choke in this warmer weather.
I am assuming the bike ran well when last used