Starting problem - R100 GS with 40mm Bings

cobbster

cobbster

Registered user
Joined
Sep 9, 2010
Messages
169
Reaction score
1
Location
Newark
Hopefully the wealth of knowledge on this site can help or I buy a 1200(lol)

When ever I start the bike from cold, it takes an age to start. (Not cool and really p*** me off)

If I put the Choke on full or half the bike doe'snt seem to fire, with or with a little throttle.

If I continue trying to start with the choke off and no throttle it will try to fire, however if I twist the throttle only slighly the small chance of firing goes away.

I continue to keep the starter going, with no throttle, until its go enough umph to keep going on one cylinder, then gentle throttle either kills it or it eventually picks up on both cylinders and off we go!!!

I'm pretty sure that that I'm not flooding the carbs, I've checked the operation of the chokes and they seem to return OK. I did have to change a choke cable some time ago. I have also have serviced the carbs some time ago and dropped the needles by one notch, as the bike has a Y / T piece, no collector box. This improved the MPH by @10MPG.

Once the bike has been running it starts ok, runs fine and goes well enough.

Economy is OK, plugs look the right colour.

Any idea's?

:beerjug::beerjug:
 
Sounds like your cork gaskets have gone oval around the choke pickup tube. If this happens then putting the choke on allows more air in weakening the mixture. A couple of new cork gaskets should sort you out.

I had the same issue years ago. Took me ages to find.
 
Thanks Rob, do you mean the gasket with the 4 screws that seats the choke carb?

Regards

:beerjug::beerjug:

PS. May not need to get a 1200 then (lol)
 
Thanks Rob, will undo the clips and drop the float bowel, after getting two new gaskets.

Question, how does this effect the choke? trying to get my head around this?

Regards


:beerjug::beerjug:
 
The choke citcuit draws fuel up from the float bowl via the small brass jet in the bottom of the float bowl. To draw the fuel though this jet it needs a seal to be in place around the float bowl to carb gasket surface. The cork gaskets, especially the crap motorworks copies, have a tendency to go oval around the two holes letting air leak in instead of drawing fuel up into the choke circuit.
When you put the choke on you effectively put the air in through thevair side of the choke circuit and even more air, instead of fuel, from the fuel side of the circuit. The mixture is so weak in this situation that your bike will not fire at all. Shutting off the choke restore the mixture to it's normal running mixture and the bike will eventually catch and run.

I spent hours trying to sort the same problem out on my 100/7 years ago. Eventually, after resisting the urge to torch it, I sat down and worked through the fuel circuit. Two new gaskets and it was up and running straight away.

I posted pictures of the fuel circuit on a previous thread when somebody else had the same problem as you're having.
 
Thanks Rob for the feedback, your a star!!

Won't set fire to it now. (lol) or buy a 1200

:beerjug::beerjug:
 
eyup mate sounds like the problem I had, turned out to be a doggey connection on one coil on the HT side

Steve

cobbster said:
Hopefully the wealth of knowledge on this site can help or I buy a 1200(lol)

When ever I start the bike from cold, it takes an age to start. (Not cool and really p*** me off)

If I put the Choke on full or half the bike doe'snt seem to fire, with or with a little throttle.

If I continue trying to start with the choke off and no throttle it will try to fire, however if I twist the throttle only slighly the small chance of firing goes away.

I continue to keep the starter going, with no throttle, until its go enough umph to keep going on one cylinder, then gentle throttle either kills it or it eventually picks up on both cylinders and off we go!!!

I'm pretty sure that that I'm not flooding the carbs, I've checked the operation of the chokes and they seem to return OK. I did have to change a choke cable some time ago. I have also have serviced the carbs some time ago and dropped the needles by one notch, as the bike has a Y / T piece, no collector box. This improved the MPH by @10MPG.

Once the bike has been running it starts ok, runs fine and goes well enough.

Economy is OK, plugs look the right colour.

Any idea's?

:beerjug::beerjug:
Click to expand...
 
I have been having exactly the same problem, of late, I too was told to check the choke circuit. I will try replacing the float bowl gaskets, now though.
 
Well I've changed both gaskets on the carb float bowels, this did'nt make any difference????. Both bowels looked clean and had fuel in them???

When I get the bike going from cold eventually, if I put the choke on it chokes the bike and starts spluttering and when I put the choke off it sits there ticking over.

Did @150 mile on it today and it works fine?

I still think there is something wrong on the fuel side, but that could be my error?

If electrical surely this would be present even after starting and running?

Any idea's folks?

:beerjug::beerjug:
 
Could be the float levels, but they have to be a long way out.

Easiest way to check is to put the bike on the centre stand, turn the petrol on and off to fill the bowls, then remove one bowl and measure the depth of fuel in the centre - with 40 mm carbs you want it around 24/25 mm deep.

Replace that bowl and refill the system before removing the other side, this seems to stop the fuel in the hoses draining into the second bowl and upsetting the reading.

Once you have found a level which works for you scribe a line inside the bowl so that checking is easy the next time - in my experience it doesnt take long to change, especially if you gave fitted new components.
 
Beemerboff said:
Could be the float levels, but they have to be a long way out.

Easiest way to check is to put the bike on the centre stand, turn the petrol on and off to fill the bowls, then remove one bowl and measure the depth of fuel in the centre - with 40 mm carbs you want it around 24/25 mm deep.

Replace that bowl and refill the system before removing the other side, this seems to stop the fuel in the hoses draining into the second bowl and upsetting the reading.

Once you have found a level which works for you scribe a line inside the bowl so that checking is easy the next time - in my experience it doesnt take long to change, especially if you gave fitted new components.
Click to expand...


Thank Beemerboff for the advise, I did'nt measure the depth but both bowels seemed pretty full of clean fuel. I do believe its a fuel starvation problem but I could have that completely wrong?

If that was the case would'nt the bike starve of fuel if you were riding it really hard which I have been today?

Will check next weekend when I get chance.

:beerjug::beerjug:
 
I've got 2 ideas
1
because you have a non standard exhaust could it be that there is too easy an airflow and a little back pressure is needed ??
2
If it works when you have poured a kettle of hot water over the carbs to warm up up - could it be the atomisation of the fuel ?? do dah above the main jet is gunged up
Sorry if these are shit ideas but mine starts well and I have never had these problems - but I bet I will soon as I have posted this drivel :D :augie
 
Very interested in this thread as have exactly the same problem with my 92 r80gs.......when starting from cold the bike eventually tries to fire up on one cylinder but if i give it any throttle it dies.Once engine started and warm it runs like a dream and will restart on first press of the button.
Have had carbs rebuilt and ultrasonically cleaned,new HT leads and battery but problem is still here.
 
I think this problem ( and the leaky carb ) are two of the 'black holes' of ownership of an airhead. I've owned a few of these and some do, some don't :confused: All ran perfect:nenau

Also, the boiling/very hot water over the carbs ( my theory ) is that it causes the metal to expand and cons the little bugger into thinking it is summer and the slide etc works better due to the metal expansion.
 
Hi

The problem with diagnosing starting difficulties is that everything has to be absolutely right to get easy starting when the engine is cold.

The most common causes are:

(1) Float bowl gasket (as Rob said)

(2) Coil (as Jaber said) (When starting a cold engine the voltage across the coil is lower than any other time)

(3) Blocked enrichener jet (in the carb bowl)

(4) Air leak on the gasket(s) on the enricheners

(5) Blocked hole(s) in the disks in the enricheners

(6) Enricheners removed and parts replaced on the wrong side carbs

(7) Choke lever not actually moving the enrichener levers on the carbs

Hope this helps


Steve
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
You must log in or register to reply here.

Similar threads

Vulpine2
40mm Bings. Slide wear
Replies
1
Views
642
Smug
Smug


Back
Top Bottom