Hot and warm pipes

[Cadmandu]

I am in the middle of rebuilding my carbs on a 85 VF700C. When i got it the bike would start with half choke but when i measured the temperature with an infared gun the 2 and 4 cylinder were 160 deg F and the 1 and 3 pipes were 525 deg F So I decided that the carbs needed cleaned and rebuilt. I found that the air filter was very clogged with a mouse nest as well. The coils on the 85 are supposed to read 2 ohms primary I will check that soon. I got a kit from Billy C and a book on carbs from the motorcycle project Mike Nixon. I cooked them in an ultra sonic bath and will be putting them back on the air box this weekend. I read that when you want to check the spark you should remove the one plug from each spark box and ground both if you do one at a time you can damage the electrical components why?