hi all,

i have a 93 r100r and am having some troubles with the choke on start up.

if i try to start the bike with full or half choke when it is stone cold in any conditions it just won't start. it feels like it is getting choked too much.

the bike starts fine with no choke and a bit of throttle, but i have to hold the throttle on to stop it from stalling till the bike warms up.

when the bike is running but still cold and i put any choke on it stalls straight away.

i have checked that the choke is closing properly and have lubed the cables. i also experimented by manually applying the choke on each carby one side at a time, the same thing happened.

does anyone know what the problem could be?

cheers,

chris

You could open and clean the choke assembly (four screws towards the engine). Be sure to not mix up the parts between the carbs.

Before you do that you should check the gasket on your float housing, if it’s not sealing the einrichtner will not be able to suck petrol but it will suck air and make the mix leaner. You should also check that passage to the circular hole is open (in the float housing)

i have now rebuilt the carbs replacing the gaskets, o-rings and diaphrams and cleaning with carby cleaner. however i am still getting the same problem on start up.

anyone got any ideas?

I would leave well enough alone and be thankful that it starts and that you know the knack. If it ain't broke don't fix it.

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The electric monk always has faith.

What happens if you apply choke when the engine is hot?

There are two ways of putting the choke assemblies on the carbs. Needless to say only one way is correct. Also it is possible someone mixed up the two choke assemblies. This is easy to do. as a final note, probably not needed, the lever pulls the chokes on. lever closed equals chokes off ( but only if they are fitted correctly.)

You need to physically clear the little jet that feeds the choke assembly. compressed air is not enough.

It would help, possibly, to know where you are .. if it is over say 30C then the choke may not be needed ...

It should be possible to apply say 1/10 choke and see if the idle is ok when cold ... if even that kills the enging I'd be very carefully checking the chokes have not been swapped from one side to teh otehr .. or simply put back together wrong .. possibly by the previous owner..

We're all assumeing the thing is standard..

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Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S

the bike is standard apart from having a k and n air filter, and the problem existed before i changed the filter.

i bought the bike with 15000ks in close to perfect condition about 6 months ago, it has now travelled 40000ks.

it appears the problem is worst when it is very cold, when it is below 10 deg C i sometimes have to roll start the bike.

i have changed the battery and plugs.

OK - so we have
Standard bike (with K&N air filter - but was doing teh same before fitment)
New battery
New plugs

Reluctant to start with choke - worse below 10C
Dies if either left or right choke (or both) activated when cold

Easy to start with a little throttle ..

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Did it always do this (under your ownership)?
Are you getting reasonable fuel economy? (bike is not running rich - thus choke can flood engine)

I think it is the choke circuit .. wrong assembly of components ..

__________________
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Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S

it starts easy with throttle at average temperatures, say around 20, but below that it is even hard to start with throttle.

my fuel economy is around 6L/100kms, but goes to about 7 in heavy traffic. do you think that is about right?

Your mpg is in the ball park.. I still think you need to sort out th chokes, What worries me ii if both are wrong, then the most likely cause is they have been swapped over. Why the change to K&N filter ???

One of our R65s pulled a choke cable through the lever on the handle bar. This meant that one choke was not closing at all, took quite a lot of hunting to find as the choke cables appeared to be ok.

Try and work through the logic of why it wont start.

Choke closed means fuel should be rich - too rich and it wont start as there is too much fuel and not enough air. Is there a strong smell of fuel coming from the exhausts when the chokes are closed? Yes = chokes are working, No = chokes are not closing.

What about the carb jets? They do wear, but 40000kms - maybe need to rejet the carbs with new needles, jets and seals.

Have you fiddled with the electronic ignition timing module? What about the sensor for the timing? I'm not sure if there are any DIY tests for the electronic ignition, maybe someone else can help on that.

The Bing carburettor does not in fact have a choke!
A choke does exactly what the name says, it chokes the air and in the process enriches the mixture but the amount of fuel flowing through is still the same.
What is fitted to the Bing carbs is in fact an enrichner and it allows more fuel through the carb but the airflow stays the same in this way enriching the mixture for starting and idling of a cold engine. This have only one major drawback, as soon as you open the throttle you allow more air trough the carb leaning out the mixture again.
The secret of starting the Bing carb with the choke on is that the throttle should stay closed till the motor start, as both carbs start firing you can add a little throttle for some seconds after which the bike should idle with the choke on.

I must add that Bing carbs are very temperamental when it comes to cold starting and it always vary from one bike to the next, but it takes only about half a mile till you can switch of the choke and if they are well maintained and balanced they will run like a dream.

There will be a L for Left and R for right stamped inside both the enrichners so it will be easy to identify which should go where.
If you took them apart to fit new O-rings and are not sure that they are assembled the correct way around I can post some pics here to illustrate what it should look like.

Right, forget the choke problem, we're now looking for something completely different, an enrichner problem

Reminds more of a song from WW2 .. about making a thing-a-ma-bob that turns the whatchamacallit?etc ..

BMW operators manuals calls it a choke - so the average user calles it a 'choke' ..

It is better to be nearly right and understandable
than to be academically accurate and incomprenhensible.
Author unknown

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Think we are all agreed something is worng with the assembly of it .. left to right swap or whatever .. need close examination and comparision with diagrams/photos of a good one..

__________________
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Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S