I cant start my motorcycle

If you change the exhaust pipes, you have to sync the carbs (if you cant sync them, you have to change the carb jets), usually it is backfiring because the carbs are not in balance.

Replace the starter solenoid.

Have you checked your fuses?

F-I is fuel injection system telling you to clean air-filter,fuel-filter and clean the fuel injector system. This is a good start.

have you checked all the fuses? and make sure you're terminals are clean and tight.

It sounds to me like you have a faulty ignition ciol If you are able to borrow one off a mates bike of the same model & try it if you find your machine starting with the borrowed coil get the to a dealership not a wrecker in my expierience( somthirty odd years of it 0 second hand electrical parts will only give you trouble all the best .Geoff

any battery that has been completely flat can often get whats called sulphated plates if this happens the battery may never recharge and if it did take some charge it wont be much good after, the battery has had it realy the only this you could try is a very slow long charge but even this may not work,,,as a last dich try putting an asprin into each sell,,, yes thats right an asprin it dose work some times but for the life of me i dont know why, it just dose! as for whats the best battery,,,its all down to price at the end of the day, if its a cheapy type battery it wont last very long but il give you a good tip,,,,buy your self a 12 volt solar charger of say 2.5 watts a 1.5watt will just about do for a small battery,, when your going to lay the bike up the next time hook up the solar charger to the battery and forget it,,, the solar charger only needs daylight to work but sun light is better, and it will keep the battery toped up all winter i use them on my bikes (BMW 750cc 35amhr battery fitted) put on at the begining of winter took off in spring and they start first time every time,,,free power,,good huh!

The problem will be gummed up carbs or injectors which ever your bikes have.

Clean the carbs!

Start by checking the battery. Turning on yer bike and letting it idle is gonna drain the battery over time. Check the charge with a voltmeter. Should be at 12.5 Amps at least. If it is, I'd check the battery cables next for good tight clean connections ( if u dont have one - get a charger)
If that dont do it - get back with me - I got more