i often read/hear about starter issues its a simple fix in most cases the cables are too thin with corroded connections and crimped not soldered also some models like my st2 have the solenoid next to hole in the fairing just right to get wet 
if you replace the battery positive and negative leads with thicker stuff from the car world solder the crimps move the solenoid to next to the battery and replace the starter lead too lots of terminal grease hey presto no more starter issues no need to buy one of those super expensive high energy battery,s ive done this as a cure for the prob on my 900ss–and both st2,s 
Hi yes most people have done this with improvements but the standard batteries Yuasa still let you down. Fitting a motobatt battery from ‘mad 4 bikes’ makes a massive discount and Paul has even got us discount now for members
+1 on what Cheshire Cat’s said, I carried out everything that you’ve suggested and fitted a Hawker Odyssey (Motobatts are a cheaper copy of these) however seven years down the line the battery was on it’s last legs, so I’ve recently fitted a Balistic $$$'s.
But the bike still struggled on the button?
It turns out that the starter motor was F’kd, the magnets had all but completely lost their magnetic flux, I dug out a spare 2nd hand starter, rebuilt it with a £15 kit I found on the net and everything is as it should be once again.
20 odd year old starters and 7 year old batteries don’t last forever even if you fit them with heavier cables.
My bike (mentioned above) is a '92 851/916cc with just under 48,000 miles on the clock, it had a professionally rebuilt starter motor 11 years ago (around £100) and it’s on it’s 3rd or 4th sprag clutch now.
Steve R