Advice tuning flat slide Mikuni

At 3/4 throttle you are metering off the tapers on the needles. If you raise them one notch, the miss should go away. If it doesnt, the taper on your needles is either too slow or you are winding the throttleon too quickly. Main jets usually don't do much until you use full throttle, and itis normal to have them slightly too rich. For best performance, slow taper needles are better and wind the throttle on in a controlled fashion. Most road bikes probably have quicker taper needles to cope with heavy-handedness.When I tune for racing, that miss you have at 3/4 throttle is important. If you do not get that and then richen very slightly, your motor will be too too slow. I get the miss then raise the needles one, I also use the slowest taper needles.
Lack of throttle response with a Commando motor is bullshit - the problem is the heavy crank combined with quick taper needles - the mixture richens too quickly.
Plug colour is usually only an indication of what is happening when you ride the bike full blast. It is possible to meter off the tip of the needle. So if you fit larger main jets, it should change the plug colour - the black ring on the porcelain shoud widen. It indicates the rate at which the carbon burns off. So use hotter plugs for tuning and cold for racing.
The taper on the needle is there to compensate for loss of vacuum. If you whack the trottle open on a race bike, the motor should gasp. Just feed it on, and the bike will accelerate quicker.
It is one of the things I love about my Seeley 850, I makes me happy just thinking about it.
 
At this time 220 main jet, middle ring on 6DH3 needle, #4 needle jet- jet needle, 1.5 air jet I am also running 2 inch long velocity stacks



Colortune plug? Sorry never heard of these. Where do I get them. Never to old to learn new trick
 
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mean gene said:
At this time 220 main jet, middle ring on 6DH3 needle, #4 needle jet- jet needle, 1.5 air jet I am also running 2 inch long velocity stacks



Colortune plug? Sorry never heard of these. Where do I get them. Never to old to learn new trick
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Colortune kit is an insert plug that lets you inspect visually the color of burn throughout the range . The goal is Bunsen blue .
 
Torontonian said:
Colortune kit is an insert plug that lets you inspect visually the color of burn throughout the range . The goal is Bunsen blue .
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There's a big industrial estate near me where I test my bikes at night
I've used colour tunes in both sides glancing down at different throttle positions to see what colour I was getting in real conditions
But now I use an afr guage
 
I am an industrial chemist . With fuels, we are talking about stochiometry. Theoretically the stochiometric mixture should give the most energy. However in a motor there are other factors at play. When you get the most energy, that might be the point at whch you start burning valves and pistons, and have the most heat build-up in an air cooled engine. Colourtune plugs are probably designed to keep your motor safe,regardless of its design and fuel properties.
 
Schwany said:
I use my butt. It is a very sophisticated high tech tuning device.
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So do I, and I also use my eyes to see if the corners are arriving quicker. In the last two years, I have had the cataracts removed from my eyes. So if I race again, I will probably crash because of the fright.
 
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