Plugs
I've just checked the BP5 something something something - but cheap - plugs in the Shadow after 200 mile run. The rear plug looked OK, dark brown so maybe a bit rich, and the front plug was white with a covering of soot from the last few hundred yards on the pilot. Both pots have 190 jets. More research needed........ However the bicycle ran like silk.
Note that the plug colour needs to be observed not where I always looked, on the nose, but at the bottom of the annulus between body and core.
My race bike has the advantage of being run full wide open much of the time, so setting the mixture (Gardner carb) consists of leaning it out until 1) it stops vibrating and 2) it pops on the over-run. Then richening it one.
The ideal plug colour is best described as "dirty white". With Cosworth pistons at £250 a pop, be sure I err on the safe side.........
Road bikes are far more difficult, and one really MUST mark the throttle to find out where it is weak and where rich. Or find a good dyno man......
A point worth making is that my race bike runs on Avgas, which never changes. "There are no lay-byes in the sky". Commercial fuel varies day by day, bio-fuel is NOT the same as normal fuel, and while the computers that control normal car engines MAY be able to compensate for fuel variations, much of SE England ground to a halt while Tesco, where they all filled up, claimed "Nothing to do with us, gov". As Mandy Rice-Davies memorably remarked, "well they would do, wouldn't they?".
On jtan Carl Hungeness reported that on bio fuel he got 40 mpg, on hideous non-eco dolphin killing, pure hydrocarbon, no-subsidy-to-farmers who voted for George Bush, nasty fuel he got 45 mpg. Go figure.
Just fitted a pair of these to my well worn rapide (lucas distributer ignition) and can honestly say that i noticed a marked improvement - especially in the bottom end pick-up and tickover - it is certainly the best £12 i've spent on the bike. - haven't had a chance to take them out and look to see colour etc as i got caught in a tropical rainstorm on the way home and had to empty my boots before i drowned - I have never seen so much water falling out of the sky at once !!