Having some issues with the choke on my GS. Its current behaviour from cold goes a bit like

• clutch in, choke to about a half, no throttle hit starter. fires immediately sits unhappily at 2krpm. will burble there for a few seconds then typically die. touching the throttle here usually kills it too. letting the clutch out in neutral also kills it
• starter again, bit of cranking (a few turns, slightly slow if anything but the battery is fairly old) starts then burbles again maybe go up to 2500rpm.
• blip the throttle even slightly. revs up like mad.
• back the choke off to bring the idle down to 2000rpm or so. choke is barely on (last either of its travel at most) now. the choke is incredibly sensitive at this point - a tiny change will either add 1500rpm or drop the revs to ~800rpm.
• ride off, once its got a little heat in the engine it steadies out then gets lumpywhen its warmed up enough to turn off the choke completely, idles at 1100rpm or so until hot then its around 1300.

once warmed up its running even, pulls well past 10k, spark plug colour is a light tan (very slightly lean at idle).

carbs sync'd, intake boots fairly recent, air filter 3000 miles old, newish oil and filter. I'm fairly sure the float heights are dry measured to 14mm each. Wet testing doesn't show them particularly off the gasket level.

any thoughts? Its had some ignition timing issues of late and was running with more advance than it should (this made it rev *really* well but was terrible off the mark). but thats since resolved. all valves in spec.

the choke gubbins looks like this - neither carbs seemed too chewed up but the plungers are very slightly scored. The needles are ok though.

occasionally smells of a bit petrol just sitting there. Oil doesn't smell of petrol.

It doesn't sound to me like your bike is doing anything too unusual.  Why are you starting it on half choke?

The usual startup procedure is to put the choke on full, start it up, and back the choke off slowly as it warms.  Use the time to get your gear on and by the time you're ready it should be rideable though you'll still probably have a bit of choke on it.  I like to keep the revs between 2-3K.  Higher is fine but I have some whiny neighbors so I like to keep it calm.  Work the choke down to around normal idle before putting in gear.  Just enough to keep it from dying at a stop light and after a few blocks or miles you'll be able to run with the choke fully off.

All engines run like crap when they're cold.

I do feel a bit of a duck with it revving at 5krpm if I leave early or have to go out late at night - i'm a bit against the idea of a cold engine spinning that fast from cold anyway.

It might be the norm - I have no idea - its only ever needed half choke before but then again its running 'right' at the moment (Which its not done so before) so maybe I just need to relearn the choke

Quote from: tobyd on April 16, 2019, 02:25:40 PM
It might be the norm - I have no idea - its only ever needed half choke before but then again its running 'right' at the moment (Which its not done so before) so maybe I just need to relearn the choke

Yes.


It's the same with my Ducati.  If I'm trying to be polite and only half-choke it, it'll often start up just fine but will idle unhappily and occasionally sputter and stall.
It's proper to start a cold engine with the choke fully on and, as Kilted1 explained, back it off as engine temperature rises.


You don't have to worry about the engine spinning "that fast" when cold.
Revving it to 10K right on start up?  Not recommended.
Revving it to 3-4K when the redline is, what is it, 14K?  Nah, not a problem.

+1 for sounds normal. If you try to start it at half choke instead of full choke it will require more babysitting. I do the same thing when I feel like it's too early or late to be blasting my neighbors with 5,000 rpm for 5 minutes. Often it will die a few times through the process as it's hard to gauge exactly what the bike needs. Full choke for 3 - 5 minutes is the fool proof method but I agree it is loud, especially if you have the Vance and Hines full system like I do!

I start on full choke put my helmet and gloves on. Sit on the bike and reduce to half choke and ride off. Two miles later reduce to 1/4 choke and by the time I get on the faster roads I can turn it off.

Sounds normal. I currently have a similar issue (in terms of stalling) however when I first start her up on full choke it only reaches around 2K RPMs without me touching the throttle. Trying to fix with gas overflow in the left carb I think.

Its seems to respond fine to what sounds like normal operation. Full choke, sort of burbles at 2 or 3k for a bit then revs up to 5 or so and I back it off to 2k and ride off and after a few miles (or it gets lumpy) back it off completely.

I'd like to report more but the head bearings eventually gave up (they've been doing well considering the adjustment was upside down and only finger tight) and its un-ridable until I replace those....

Quote from: roxxer69 on April 21, 2019, 09:08:01 PM
Sounds normal. I currently have a similar issue (in terms of stalling) however when I first start her up on full choke it only reaches around 2K RPMs without me touching the throttle. Trying to fix with gas overflow in the left carb I think.

sounds like a burnt valve.  I had the same, burbling and low choke rpm start, turned out it was an exhaust valve burnt and chipped valve guide. 

Quote from: tobyd on April 22, 2019, 01:11:51 PM
Its seems to respond fine to what sounds like normal operation. Full choke, sort of burbles at 2 or 3k for a bit then revs up to 5 or so and I back it off to 2k and ride off and after a few miles (or it gets lumpy) back it off completely.

I'd like to report more but the head bearings eventually gave up (they've been doing well considering the adjustment was upside down and only finger tight) and its un-ridable until I replace those....

Sounds normal to me. As said, don't worry about revving it to 5k when cold, as long as you're using good oil of the right viscosity your engine will still be protected. It'll wear a little faster than when perfectly warm no doubt, but it's not going to be anywhere near metal on metal or anything like that.