I had a few questions when i got mine too. But it's really simple. Just rig all of them up just as tho you'll be using them all. Why, i dunno, but thats what i was told and thats what i did. It may have to do with getting the proper vaccum or something, but in any case just rig them all and only use 2. But theres also a reason why it's good to put them all on. You will find that they may not all be accuratly the same as each other. so it's good to try them and find the 2 that are closest to each other. What i did is try each one seperatly on one carb till i found the 2 that both registered close to the same. Turn your idle setting up to about 1500 then attach one of the tubes to either carb. Rev the bike slightly (not too much because if you go too high you can suck mercury into the carbs, tho it takes quite a bit b4 that will happen)a few times and note where the mercury tend to always settle as it goes back down to idle. Remove the tube and attach the next one to the SAME carb and note where that one settles. Do this to all 4 and note which 2 are closest and always use those 2.
To assemble it, push the little restrictors (those lil plastic cups with the tiny hole in them) into each tube so it's near the end you attach to the tubes of the gauge. Also note that after you put the mercury in the gauge it will take a while before it works right because before it has time to settle there will be air in it that will cause the mercury to have bubbles in it. You'll see what i mean when you 1st try it. That will go away after messing with it for a while.
And finally, if you cannot find 2 of them that are very close as i described earlier, you can take a pin a slightly enlarge the hole in one of the restrictors that is registering LOWER on the gauge that another one in order to get it to register higher and match one of the other ones.
It all sounds like a pain but it really isn't, and as for enlarging one of those holes to get 2 gauges to match, i didn't have to do that and you probably won't either. But i mentioned it just in case. And once i found 2 that matched i took the 2 i don't use and rubber banded them to the back of the gauge to keep them out of the way and so i'd know which 2 to use.
