Truck6 - ditch the stock battery altogether and replace it with a little sealed 12v lead acid battery. You only need enough juice to run the brake light and turn signals at idle. Any more than that is just extra weight. Plus those sealed batteries cost less than buying a new Yuasa for the bike and last forever.
I ran my XT350 on a little Honda push mower battery doing souble duty starting the lawn mower and being in the bike. It was maybe the size of two packs of cigarettes, about 1/4 the weight of stock, lasted for years and it won't spill while you are crawling out from under the bike. It works 1000x better than stock or using a capacitor type battery eliminator.
And +1 on removing the cams to replace the shims. Mine only needed new shims like two or three times in 17 years. So don't stress over the Yamatool. If you need new shims just pull the cams. Be careful though because the cams run directly on the head casting. And you really, really need a Clymer.
PM me if you can't eBay or Amazon one.
KTM 640 LC4E
KTM 200 MXC