Well, it's definitely cooled down enough in the southern states, and there's lots of new riders experiencing their first winter, so thought a post on the choke would be useful. If you have a fuel injected bike disregard, as your bike does it all for you (ya bastards!). O.K, the theory behind a choke. When starting a cold engine, the incoming air is cold and travelling very slowly, compared to when the engine is running. This makes it more difficult for teh carburettor/s to atomize(mix up in air) the fuel. The choke serves to add extra fuel to the incoming air, ensuring combustion in the engine. A cold engine needs significantly more fuel, even when first started and running, to make up for fuel that is not atomised (usually pools in the intake, passes right through the combustion chanber unburnt etc). There are two type of choke mechanisms on motorcycle engines, one is an enrichener, and the other is a choke plate. The enrichener works by adding extra fuel through a small port in the carburettor wall. It is a simple plunger type setup, more choke you pull on, more the plunger travels, and more fuel can be admitted. The choke plate type works by restricting the amount of air entering the carburettor. It creates a higher vacuum on teh engine side of the choke valve, and this higher vacuum draws extra fuel out of the idle and transition circuits of teh carburettor (adds more fuel). Correct use of choke is to FULLY engage the choke when cold cranking and use no throttle. As soon as the engine catches and starts to run, trickle on some throttle. You will need some judgement with your particular bike with regards how much throttle to add. As soon as the engine is up and running, reduce choke as far as you can without the engine starting to stumble. When the engine is running smoothly on the choke, you should be able to let the throttle return to idle. It is normal for the engine to rev higher on choke, even with no throtle. You can safely leave the engine do it's own thing with some choke on, put your gloves on etc as it warms up. You should slowly keep reducing choke as the engine needs it, some bikes will take a few seconds of needing choke, some more. Again, experience and judgement will work. It is even normal to need a little choke to ride off with on cold mornings. A good test to see if you need choke is to blip the throttle lightly. If the engine stumbles just off idle, you need some more choke. Remember of course, to return the choke to off as soon as reasonable, again, use throttle blip to see if you need it. Smooth blip, no need for choke anymore. Sometimes, rarely, you may flood an engine (flooding is when you allow the engine to draw too much fuel in and the fuel/air mix is either too rich for combustion, or liquid fuel has coated the spark plug, allowing the electric current to run straight to ground with no spark) using too much choke. It is pretty hard to do on a bike with a healthy ignition system, but if you do suspect flooding, you need to know how to identify it and correct it. If you have flooded the bike, you will notice either a strong fuel smell, or liquid fuel running out of the exhaust somewhere. If the engine is turning over, and occasionally firing on one cylinder, it is NOT flooded. Use more choke. If you do flood an engine, the best thing to do is walk away from it for a few minutes, the restart with NO CHOKE and full throttle till the engine catches, and if it doesn't start after catching, reapply choke, but less this time. Probably the very best way to start a badly flooded engine is roll starting down a long hill. A side not to cold starting an engine is engines with vacuum fuel taps. Sometimes, the carburettors may have the fuel evaporate otut of them if left for a couple of weeks, leaving very little fuel in the carburettors. Normal cold crankng of the engine does really not provide enough vacuum for the fuel tap to flow fuel, so you should switch to prime and crank on prime. This allows fuel to run to the carburettors regardless of engine vacuum. An engine not starting is fairly frequently caused by this, and can be misdiagnosed as flooded. Try prime position if the engine has sat for a week or so. So, there is absolutely nothing wrong with using choke, it is not a sign of a badly tuned engine that you need choke for cold starts, nor is it bad to ride off with SOME choke. Remember, the choke is there for a reason, use it, but use it properly. Consult your owner's handbook for any pecularities for your bike. And remember, a well maintained ignition system is your friend on a cold, winter morning, as are well maintained carburettors. Spend the money to aviod much frustration! Regards, Andrew.