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 :mchappy:

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.

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.

[quote=don't warm up the engine standing still. .[/quote]

Should I do star jumps while the bike warms up? :biggrin3: 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!)

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!

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?

Good point, well made, I've obviously been sat idling too long!
Hi Ho Silver......

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..

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.

Engine warm-up and tackling slopes at the outset
 

Well I think I've got the hang of the choke now - it's all about listening to the bike, simple! More by trial and error than anything, I've got used to the different happy and sad sounds the bike makes with less or more choke (!) and adjusted my approach accordingly.

Still not sure how long to leave the engine running at a standstill before taking off though. In order to get out of my underground garage, I have to tackle two quite steep slopes right from the outset, which seems to demand a lot up front from the engine when it's still not fully warmed up. I gave it a lot of throttle this morning to get up the slopes (then stalled near the top of the second, which wasn't funny as I had the full weight of the bike to hold while I re-started the ignition!). So I'm thinking maybe I need to let the engine warm up for longer than if I was just taking off down a horizontal road...??

Jeanie :mchappy:

choke use depends on the bike. every ones different.
my XT600E needs full choke to start anytime unless its already warmed up, start and then immediately put on half choke till it'll idle without. you can ride with the choke out ok but idling will be very high. being aircooled you can ride straight from starting no problems, in fact you shouldnt leave an aircooled bike idling for too long because theres no cooling. i have been stood chatting with the choke out before and turned round to see the downpipes glowing red hot!

a watercooled bike is the other way, it takes longer to get up to temperature and you should let them warm up a little even if its only for a couple of minutes while you get your helmet and gloves on.

neither style of bike should have its neck wrung till its warmed up properly of course, but gentle normal riding is fine.

even my varadero has a "choke" (its not a proper choke, being fuel injected it doesnt need one, its just an air valve in the inlet) for a little help on really cold days. otherwise the ECU sorts the fueling out for you.

If you want a really dumbed down expanation for a choke:

Your engine burns a mixture of air and petrol..

When the engine is cold, the engine likes more petrol in the mixture than usual.

The choke usually "chokes" the air supply into the engine so it gets more petrol than usual. Hence it's name.


You should start the bike from cold with half or full choke depending on how cold it is. After 30 seconds is usually enough for most bikes. Especially a small thumper.

Just reduce the choke slowly. If it wont idle smoothly (sounds like an asthmatic pensioner) then it probably wants the choke on a bit longer.


NEVER run the choke longer than you need to. It will soot up your spark plug and all that extra petrol will increase wear on the engine (it thins the oil in the combustion chamber)

Thanks for your advice guys. :thumbup1:

Still experimenting with the choke, as I don't think I've quite sussed it yet. The Marauder seems to need a LOT longer than 30 seconds of choke - the engine just splutters and dies if I try and reduce it even after a few minutes. I usually start it with half choke as opposed to full choke - at full choke, it very quickly revs far too high, prompting me to reduce it to halfway where it then sits and idles nicely as it warms up. After about five minutes, though, still unable to get the engine to idle in neutral without any choke at all, I've been riding off with the choke still partially applied, then shutting it off after a few minutes on the road. Not sure if this is good for the bike :confused1: but it seems to work...

Jeanie :mchappy:

IMHO don't get too tied up in this. The choke/enricher/increased idle device* is just there to get the thing moving. If the bike is warm enough to go where you need with the cold start device on, then go. If it stalled, chances are it would have been fine with a bite more throttle or waiting 30-seconds, it doesn't really matter which. The internet theorists are going to howl about wearing the engine out faster, but in the scheme of things you'll be knocking tens of miles off the life of components that should be lasting hundreds of thousands. I wouldn't idle a bike in an eclosed garage for long, think of all the soot and rubbish you are breathing in.

* the last bike I saw with a choke (restricted air supply) was a Dnepr, say no more, this is 1930's technology! Most carbed bikes have an enricher circuit. The cable goes to a plunger on the side. Pull the plunger up and there is an extra passageway to let more petrol into the engine. The bike runs richer, so uses more fuel and will eventually foul it's plugs. (If you ever own a Guzzi, the O-rings swell, the dealers tune the bike to run on constant choke and the *****y thing does 15 mpg :( and fouls the plugs every 50 miles :thumbdown:). When you clean the bike, have a feel of the choke cable operation, you should feel it close. FI bikes just have a switch that tells the computer to let it idle faster to avoid stalling. The fact that the Berlin-Munich loons decided to put said switch on the end of a steel cable is beyond me, but we are talking about the blokes who designed an indicator switch set that needs three thumbs!

Andy

True.. But I was trying to put it in a way a novice would understand... The theory is the same.

:innocent:

The Dnepr had one huge advantage, the choke was just a sort of shutter on the air box. Even the bloke who put the thing together after fifteen pints of Vodka couldn't fail to notice if it was working or not. Bings rubber plunger on a cable over the passage into the float chamber thingy on the other hand....

I hate carbs BTW, it's the electrical engineer in me, open loop control, setting by half a turn here, lift the needle a gnats whisker an all that. Give me early 90's Bosch every time :rofl:

Andy

Ahhhh, my 1983 HONDA XL500R uses a "choke plate" :clap:

The fuel mixture needs enrichening (increasing the fuel quota in the mix) when the motor's cold, because the fuel tends to condense on the cold engine surfaces until at normal running temp! which = lean mixture.

The bikes (with carbs) that need choke for extended periods, are most likely running on the lean side :frown:

Later model carb bikes were purposely designed to run a tad lean - this is to help get thru emissions limits.

It's all easy once you learn the requisite voodoo. There's a lot to be said for a toolkit consisting of two screwdrivers and a pointy stick.

Anyway...

My KLR likes full choke first thing in the morning, no extra throttle. Once it's running I let it idle until it reaches 100 degrees F on the temp gauge, then open the choke fully. That's just time enough to put on my helmet and gloves in decent weather. Get on the bike, blip the throttle to be sure it's warm enough not to die when I give it some beans, and away I go.

Yes, I know, it's got an enricher, not a choke. It does the same thing, only backwards.

I'm fascinated to hear what repair functions you use the pointed stick for, Donald! :clap:

General purpose poking and prodding and pushing and rubbing and scraping and things like that. Pointy sticks are also good for absent head scratching while you figure the best way to apply the screwdrivers.

Pointy sticks are go!
 

OK guys, so "one pointy stick" just went to the top of my shopping list of essential items - I'm convinced!

I especially like the idea of it as a head-scratching device, as I think I will be doing a lot of that as I get to know my new bike over the coming weeks and months!! :laugh:

Jeanie :mchappy:

It's for chasing the Demons out of the carb after they've sprinkled the chicken blood in a pentagram and danced naked in the moonlight :rofl:.

The MZ (one tin can full of petrol) I can do, the Bonneville (diaphragms and throttle linkages until the cows come home), I dread anything going wrong worse than the sync, again, again again again. The BMW has something that can be tested with a multimeter so long as you wear wellington boots and don't smoke :biggrin3:

Andy

I've tuned up my XT 600 with K&N filter, dyna-jet stage 2 and a Dep silencer. It requires no choke what-so-ever and idles perfectly from cold, and stays that way all the time. I thought it was running a bit rich, and turned down the mixture screw to a single turn out, so every so often when I'm decelerating with engine braking I hear a little pop (thats lean enough!). I just cant believe how easy it is to start:thumbup1:. My missus has the exact same model, and hers has to be choked all over the neighbourhood! I ride every day though, she rides once a month, that could be the reason:confused1:

If it idles that well from cold then it WILL be running rich on the pilot circuit. If you're happy with the way it picks up though, it's obviously not a problem !!

Fuel consumption and the colour of the plug will contain the answer to if it's running rich, but if it's getting the extra fuel via the idle circuit or enricher you usually end up going back to stock settings to prove it. I could have thumped the Guzzi mechanic who solved the leaking enricher plungers on my dads (then new) bike by turning down the idle and mixture, they tell you the standard settings for a reason.

Andy