have you done the shake test?
hold the air filter in 1 hand, try to wiggle it
if it moves without the engine moving, your carb bolts are loose (which will mess up all manner of things to do with smooth running) and need tightening
if you put your foot down hard, is there occasionally like a jolt, like you get no power for the first ~1/2 second?
carb bolts are loose then, sort that and the idle will fix itself
tighten up the carb bolts and you get more power, better response and more economy
reason not to do it? uhhhr, none?
how to tighten carb bolts -> take off air filter cover. you'll see 3 nuts (probably) or screw heads (less likely). undo whatever is there, and remove lower air filter housing, be careful not to damaget the rubber tubing and the funky metal spaceage lookin stuff (both just pull off, or you can leave the space age stuff off and just move the housing away, but be careful, cos its fragile (But it can be swapped with some off a 700)
you'll see another host of nuts or bolts below the housing - 4 or 5 maybe. tighten them all up to a reasonable level, like pretty tight, but not super tight
then try to undo, if its easy, your threads are knackered and you need a newer carb, or you can simply drop a shitload of superglue down the holes and try again (cheaper, will last a while). if not, re-tighten (to be on the safe side)
Replace the air filter lower housing, making sure you put the little rubber pipe back on (cos the fricken thing is alwasy forgotten) and the silvery stuff then replace the lid and treat the thing to a new filter, it probably hasn't been changed since the dark ages
You may well want to do a tune up, as you've now fixed the air leaks, if you've adjusted the screws to try and make it run properly you'll have screwed up the tuning, but DO make sure the engine is completely warmed up, ie: first time the fan comes on cos the oil heats up slower than the water, and the engine aint fully warm till all the oil is warm. The oil won't be fully hot even when the fan comes on, but its certainly well warm enough for us to do our adjustments.
The best way to do this is using a gas analyser, and you'll want to set the CO to about 2.0%. If you haven't got one of those, there's a way round it. Screw the mixture out until the idle speed is at its highest and smoothest. Readjust idle to about 950 RPM or so. Then screw the mixture in until the engine revs JUST slow down about 50RPM or so. This should bring you to under the 3.5% needed to pass an MOT. It can always be checked or corrected later.
tadaaa! your problems are fixed, and you dont need to be a postwhore to do it (thats my job)
( should be bolts but not nearly as funny LOL )
