I generally have good results with NGK plugs, I'll have to check the plug numbers on my bike. I will strongly recommend that you
NOT use Champion sparkplugs in your bike, however - never had any good experiences with them in any motorcycle or car I owned.
There are lots of sources of info on airhead carb adjusting, some of which is at least a little bit contradictory. In the end, it isn't all as "black magic" as it may sound, but there is some trial and error, and it can take a while to develop the right "ear" for it, as even when adjusting multi-carb engines with a set of mercury gauges or rotameters it still helps greatly to have have a sense, or "ear" for how the engine is running.
Some useful (and even more wordy than me, and wiser) info can be found on snowbum's website at this link:
http://bmwmotorcycletech.info/techindex.htmThe Bing manual (can be ordered in the U.S.A for around $10, I think) from the Bing agency's website has some useful tuning info, though I have found that the procedure which they describe is not the best written process, it is technically accurate. Bing website is:
http://www.bingcarburetor.com/Have you had the carbs apart for cleaning or adjustment before ? I *think* that you have type 64 Bing carbs on your bike ... IF the carbs are clean and otherwise properly adjusted for balance with some sort of gauge set, one would turn the mixture screw (bottom/underside of carb near the center and toward the "front"(mouth going into the head) clockwise (as viewed from the screw head/lying on the ground) to allow more air/less fuel (lean mixture). First, make sure the bike is warmed up by going for a 10 minute ride around the neighborhood before returning to your garage - don't ever try to adjust carbs with a less-than-fully-warmed engine or you'll get unsatisfactory results. Don't turn these mixture screws by very much at a time, and try to do both sides by the same amount. I use the "width" or thickness of the screwdriver blade as an increment of rotation. For starters, I would try turning it SLOWLY by maybe 1/8 or not more than 1/4 turn, while the engine is running, and listening for changes to idle speed. You want both sides to be running equally strong, and the smoothness of the idle - judging by a trained ear- can be almost as effective as a set of gauges, and in some ways, more useful. One might have to readjust the idle speed after this, and likely the gauges will have to be reconnected to recheck/rebalance the carbs. since many of us don't have exhaust gas analyzers or the sometimes helpful "colortune" spark plug thingie it is very helpful to put in a fresh/new set of sparkplugs so you can "read" them to help
judge if you've made an improvement in the mixture. After making some adjustments and checking carb balance, one takes the bike out for a road test to check throttle response, noticing any "flat spots" in power delivery, pinging, etc. IF these occur then one might have gone slightly too lean, for example, and have to richen the mixture back by tweaking the screw one or two "increments" back anti-clockwise.
If you haven't had the valve clearances checked/adjusted it would be best to do that first before messing with the carbs, as valve clearances affect the mixture flow rate through the carbs, and thus the balancing of the carbs. However, valve clearance doesn't have any impact on how rich the mixture is. Your fuel mileage is probably significantly lower than what it could be, with a better, leaner mixture, without going excessively lean.
What do you have for airhead manuals available ?
