You don't need the tappet tool. Find yourself a deck screw that requires a square drive to install it, this meaning it has a small square socket in the head of the screw. Now take a 2" piece of vacuume or fuel line and screw the screw into it, this is now the handle. The square socket on the head of the screw fits perfect on the top of the tappet.
You do not need to remove the front fenders to do this. Just remove the front rack and hood then from up there you can get a long extension with a 10mm (guessing size) socked down thru a hole to remove the two front gas tank mounting bolts. They have a sleeve on each of the two front bolts, so keep an eye out for them.
You will have to remove the fuel shut off control and the fuel line. You may want to have some extra fuel line because I had to cut it off the first time. I also installed a small fuel filter.
There is a wire attached to the bottom of the fuel tank that will need to be removed.
Once you get to the white barrier between the tank and engine be careful removing it. The crankcase vent tube runs thru it and I ended up with a slice in the tube when removing it from the white plastic.
Be careful removing the bolts that hold both the black side cover on and expecially the pull starter cover. Yamaha bolts break very easily, do not overtighten them and I use anitseize on all of my bolts now.
Allocate half a day for this job.
As starky said pay attention to what stroke you are on and run thru it a couple of times until you are pretty certain you are on the right stroke. I also use a McDonalds straw inserted into the cylinder, lightly, to help me visualize what the piston is doing.
Good Luck