you can either get replacement stantions (disco volante)or have them hard chromed and re-ground (philots in UK)
lowers just need stripping and rebuilding, wirth do pregressive upgrade springs
you can bend them a bit at the tips.
I always set them to the smallest gap and feel a slight drag.
BTW the things are noisy anyway so don't expect quiet, these are an aircooled 30 year old bike pre noise restrictions so don't be too hard on yourself.
mine do make a clatter and that was after full rebuild with new parts!
it all adds character to the bike
the valve gaps are for timing not noise prevention
firstly, your not a moron, its probably stuck in the socket.
i reckon a little wd40 up the inner cable to the tach and a bit of time to seep in should do it.
next time you put it back, put a little dab of coppaslip on it!
the only 2 stroke i can get is my bro's 49cc mobylette
nothing planned that weekend, so may give it a go.
looks like I'm not working the day of Lotherton, so weather permitting, I'm going to that
there is no air screw, that is metred by the air jet situated inside the intake mouth of the carb.
the pilot screw on the body near the engine regulates the fuel.
the idle screw just generally raises or lowers the revs like a throttle!
try here
http://www.reproductiondecals.com/default_frameset.html?content.html~main
http://www.sunrisegraphics.co.uk/sunrise/index.php?option=com_content&view=article&id=22&Itemid=18
thinking out of the box;
if you can get a wide thread holed oil filter, could you not make a mushroom shaped adaptor with the correct internal thread for the bike, with the external correct for the filter?
all xs400's use a mikuni bs34 carbs, but there are differencs due to emmisions legislation over time. you can get a set of carbs from another 400 to fit yours, I have fitted soem dohc carbs to my tracker with a little modding (the dohc's are narrower)
twin means 2 cyl engine
i posted a pikkies of a virago which had a rear wheel for the front.
if you have wire wheels, then lacing a different rim should present no probs except for any clearance issues you may have!!