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Using the choke when starting up a motorcycle Using the choke when starting up a motorcycle
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  #1  
Old 22 Jul 2010
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Using the choke when starting up a motorcycle
Hey guys,

Any advice or tips on the best way to use the choke on a motorcycle? Turns out my bike has got one and the mechanic recommended I use it each time I start the bike up from cold.

But how much choke should I use? How long should I keep it open? Should I use it every time I start up the bike? And can mis-use/over-use of the choke wreck the bike??

:confused1:

All tips gratefully received, as ever!

Jeanie
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  #2  
Old 22 Jul 2010
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It's one of those things you get to know.....depends on the bike, temp. how long since it was last running, which way the winds blowing....from cold when its cold I use full choke/no throttle, if you ride off with the choke on its another thing to remember as you're riding. I've had bikes that didn't like full choke, some like a whiff of throttle, some have tested my patience and endurance trying to start them. One bloke I knew pushed a bike up and down a very big hill trying to start it, he failed, and on the last run down the hill let it free wheel and jumped of as it launched into the river!!!!! Patience and understanding.
If you leave the choke on too long the bike will stutter and hold back.
If you knock it off too soon the bike will die as you open the throttle, you'll get to know the spot on the road where the motor is warm and happy with no choke and knock it off at that spot automatically.
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Old 22 Jul 2010
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Your mechanic is right. When the engine is cold some of the fuel it gets from the carburettor condenses on the walls of the combustion chamber, so the mixture becomes too lean. The choke compensates for that. It will also open the throttle slightly, compensating for the fact that the engine needs more force to turn, because the oil is cold.

How much to use depends on your bike and the ambient temperature. Start off by putting it to full on. Once the engine is running smoothly you should ride off, don't warm up the engine standing still. You should be able to put the choke back fairly quickly. Experiment, you will soon find out what works best for you.

Yes, you can do damage if you leave the choke on for a very long time: too much petrol gets into the engine and washes off the oil film, so the piston will have insufficient lubrication. On many bikes you will notice that it won't run right, but on some you don't. You will have to remember it, just like you must remember to retract the side stand before riding off.

Don't use the choke if the engine is warm.
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Old 22 Jul 2010
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[quote=don't warm up the engine standing still. .[/quote]

Should I do star jumps while the bike warms up? Seriously though, Why not? Is there a mechanical reason for this...just curious.

I always use the choke (if engine is cold) and let the bike warm up to operating temperature before closing the choke and riding away. Only takes 3-4 minutes and it feels more sympathetic to the bike (it has feelings!)
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Old 22 Jul 2010
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I think it's because you're using fuel and going nowhere:- bad for the environment. However pulling out onto a main road and stalling could be very bad for your environment!
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Old 22 Jul 2010
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Quote:
Originally Posted by garmei View Post
I always use the choke (if engine is cold) and let the bike warm up to operating temperature before closing the choke and riding away. Only takes 3-4 minutes and it feels more sympathetic to the bike (it has feelings!)
No, bikes are machines, so they don't have feelings. But you do and you can feel, or rather hear, when the engine is running right (i.e. happily). After 4 mins. the engine is getting warm, but it's nowhere near "operating temperature". For that to happen the oil in the crankcase needs to be hot. Until that is the case, the engine is considered cold, although cylinder and piston are already hot. Now, running cold causes most of the engine wear. So, you want to run your engine cold for as little as possible. When you let the engine idle cold it takes the longest possible time to warm up, so you are maximising the wear on the engine. The recommended method is to let the engine idle until it runs "round", then ride away quietly and push the choke in as soon as possible. That way the engine warms up the quickest way possible.

Of course, if you were to use the maximum power when it's cold it would warm up even quicker, but then you will damage it, because the oil is cold and doesn't lubricate the parts very well.

Does this all make sense?
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Old 22 Jul 2010
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Good point, well made, I've obviously been sat idling too long!
Hi Ho Silver......
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Old 22 Jul 2010
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Most intersesting Beddhist. I getcha.

OK, 3-4 minutes was an understatement. I usually have a smoke/lock up shed/put hlmet on etc. Basically, the bike is pretty close to operating temp before I leave as it dles smoothly and revs right (feels right). Anyways...

What interests me is the idea that the best way to warm the engine up is to ride it (gently), this being the most efficient and quickest way, thereby minimising the amount of time the engine runs cold. I've never considered this before and it does make sense.

I always thought (maybe wrongly) that it was less damaging on the engine to let it warm up on the choke (@ ~3k rpm) and then at idle before starting off. My thinking is that the higher revs used when riding would be more damamging to a cold-ish engine even though the warm up period is a lot shorter than it would be if warming up stationary.

I use the choke to 'artificially' raise the rpm's to mimic actually running the bike to warm up, so maybe it's much of a muchness. Interesting tho..
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Old 22 Jul 2010
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RTFM.......every bike is different.
I have 2 BMW's (i'm not bragging, they're both old), one has a regular choke which alters the fuel air mix, the other does not alter this mix but instead is a fast idle. Both have the same lever that says CHOKE on it.
You have to know the machine that you're riding.
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