Good luck with that. Make sure it's a good quality tap & I hope you got a spanner or something small enough to fit the end. You can hardly get on it for cylinders 1 & 4. Not the nicest job I got to say.
Ach it's not that difficult, not that difficult at all.
Yes you need to get the radiator out of the way. Can't remember what I used on the end of the tap, either a small spanner (ring spanners are always nice if you can get em on) or a 4 inch shifter.
I might be trying to tell you how to suck eggs, but just in case. As Mike says, start with the taper tap, make sure you get it in square, and once you have it established - turn it in a half or full turn at a time, then back it off and in again, work in gradually, bring it right back out now and again and clean all the crap off the tap.
1 and 4 are tight but it'll go.
Use a good quality tap.
These should be OK;
www.buckandhickman.com/find/keyword-is-m8+tap+taper/product-is-022624Has the bike been Ivanised?