Choke question

[Guest]

The choke on my ’81 GS850 is acting funny – didn’t realize it was abnormal till I made an offhand newb comment in another thread. My comment hinted that I was tweaking the throttle to get the bike started in the morning, and I was told that shouldn’t be necessary.

Fair enough, so here’s what’s going on...

1.)I’m in Arizona, but this time of year it’s probably in the high 40’s/low 50’s at 5:30am when I leave for work. I know some of you will be jealous, and I can’t blame you. I lived in New England and upstate New York for 29 years, and my hat’s off to those of you who are still riding. I couldn’t do that. My blood thinned right out after the first year living in the desert, so I can ride in stop and go traffic in a black leather jacket at 110°F. Not fun, but I can do it.
2.)The choke action is stiff. I think it’s the cable, since there don’t seem to be any parts binding on the carb itself, but I mention it for sake of completeness.
3.)Full choke doesn’t help with starting at all. It seems to want to be somewhere between ¼ and ¾ to get going, and even then, when I started it with no throttle, it’d idle at about 1000 rpm for a few seconds before heading up to around 3000 and staying there.
4.)If I pull the choke out the rest of the way to full while it’s running at 3000 rpm it sputters and dies.
5.)Not sure if this is important either, but one of the times I did that I think it backfired. I say “I think” because it was a pop, not a duck-inducing gunshot-like crack.

I’ll be honest, I’m very new at wrenching, haven’t rebuilt the carbs yet, and don’t fully understand how they work. I understand that there’s two different “circuits” at work when the throttle’s open vs. closed, and since I’m not supposed to have the throttle open when starting I assume the choke works as part of the “idle circuit”. Even if my assumption is right, beyond that I’m lost. I’ll bite the bullet and read that part of the shop manual now. Any thoughts on a troubleshooting scheme or is it already obvious what’s going on?

BTW, my bike has the CV carbs. All stock, as far as I know.

[TheCafeKid]

The choke on my ’81 GS850 is acting funny – didn’t realize it was abnormal till I made an offhand newb comment in another thread. My comment hinted that I was tweaking the throttle to get the bike started in the morning, and I was told that shouldn’t be necessary.

Fair enough, so here’s what’s going on...

1.)I’m in Arizona, but this time of year it’s probably in the high 40’s/low 50’s at 5:30am when I leave for work. I know some of you will be jealous, and I can’t blame you. I lived in New England and upstate New York for 29 years, and my hat’s off to those of you who are still riding. I couldn’t do that. My blood thinned right out after the first year living in the desert, so I can ride in stop and go traffic in a black leather jacket at 110°F. Not fun, but I can do it.
2.)The choke action is stiff. I think it’s the cable, since there don’t seem to be any parts binding on the carb itself, but I mention it for sake of completeness.
3.)Full choke doesn’t help with starting at all. It seems to want to be somewhere between ¼ and ¾ to get going, and even then, when I started it with no throttle, it’d idle at about 1000 rpm for a few seconds before heading up to around 3000 and staying there.
4.)If I pull the choke out the rest of the way to full while it’s running at 3000 rpm it sputters and dies.
5.)Not sure if this is important either, but one of the times I did that I think it backfired. I say “I think” because it was a pop, not a duck-inducing gunshot-like crack.

I’ll be honest, I’m very new at wrenching, haven’t rebuilt the carbs yet, and don’t fully understand how they work. I understand that there’s two different “circuits” at work when the throttle’s open vs. closed, and since I’m not supposed to have the throttle open when starting I assume the choke works as part of the “idle circuit”. Even if my assumption is right, beyond that I’m lost. I’ll bite the bullet and read that part of the shop manual now. Any thoughts on a troubleshooting scheme or is it already obvious what’s going on?

BTW, my bike has the CV carbs. All stock, as far as I know.

Well, while i cant say as i know exactly what is going on with your carbs/choke..it does sound like they need cleaning, and id also advise taking a look at your intake boot Orings. If you're sucking air there, its not going to help, and you'll die trying to figure it out. Most of these bikes, as ive found with mine, and from what ive read on here, seem to have a choke sweet spot. Mine doesnt like full choke either, and as a matter of fact will near refuse to start on full choke. However, i also have found that i have had a float level issue, as well as an intake leak and poor jetting this entire time, so that may be of no consequence. The "pop" you heard, if coming thru the pipe and not the carbs, is for sure a sign of lean-ness as ive learned by reading on here, so you may very well have an intake leak...a good way to find out if you do is to get the bike running, wait till she's warm and off choke, and spray some carb cleaner around the boots where they bolt to the head, and if one or more cause the bike to bog down when you do so, they are leaking and the orings need replaced. Just a suggestion, but maybe try some lithium grease or something of the like down your choke cable sheath as well, to losen up that tightness. Hope some of this helps!

[walt]

sounds like the idle is set a bit rich. have you checked the float levels? does any one carb or more leak after shutdown? also see how many turns out the pilot screws are set at? note each so you can return to those settings. you didn't say if your bike is stock. look at your spark plugs one at a time and note the color for each. does the motor idle really smooth both at start up and warm?

[tkent02]

The choke on my ’81 GS850 is acting funny – didn’t realize it was abnormal till I made an offhand newb comment in another thread. My comment hinted that I was tweaking the throttle to get the bike started in the morning, and I was told that shouldn’t be necessary.

Fair enough, so here’s what’s going on...

1.)I know some of you will be jealous, and I can’t blame you. Not fun, but I can do it.

Not jealous. Couldn't stand the place.

2.)The choke action is stiff. I think it’s the cable, since there don’t seem to be any parts binding on the carb itself, but I mention it for sake of completeness.

Oil the cable, check for kinks.

3.)Full choke doesn’t help with starting at all. It seems to want to be somewhere between ¼ and ¾ to get going, and even then, when I started it with no throttle, it’d idle at about 1000 rpm for a few seconds before heading up to around 3000 and staying there.

Full choke is for cold weather. Use 1/4 to 1/2 and be happy.

4.)If I pull the choke out the rest of the way to full while it’s running at 3000 rpm it sputters and dies.

Don't pull it all the way out.

5.)Not sure if this is important either, but one of the times I did that I think it backfired. I say “I think” because it was a pop, not a duck-inducing gunshot-like crack.

Backfires through the carbs are not that loud. Exhaust pipe fires from rich starts filling the exhaust with some fuel and then igniting are like gunshots.

I’ll be honest, I’m very new at wrenching, haven’t rebuilt the carbs yet, and don’t fully understand how they work. I understand that there’s two different “circuits” at work when the throttle’s open vs. closed, and since I’m not supposed to have the throttle open when starting I assume the choke works as part of the “idle circuit”. Even if my assumption is right, beyond that I’m lost. I’ll bite the bullet and read that part of the shop manual now. Any thoughts on a troubleshooting scheme or is it already obvious what’s going on?

Start reading.

BTW, my bike has the CV carbs. All stock, as far as I know.

Good luck with it.

[spyug]

I'd say you may have a couple or three issues.

1) Your choke cable sounds like it binding. This could be a broken stand of cable in the sheath or just plain grunge. Take it off and shoot it with WD40 or Liquid Wrench or something, it should free up if not you'll need to change it. Not that expensive.


2) It is not mentioned but do you know how long it has been since the valve clearances have been checked? If there are lots of miles on the bike and it has been awhile they should be checked as this will definitely affect starting and running. Check your manual for more info.

3) You haven't said how long its been since carbs were redone either ( if ever) so it could be that you have some split o-rings or crap in the circuits. Its likely time for a cleaning and rebuild. The carb rebuild tutorial is excellent so study up on it. Also get a hold of Robert Barr for his o-ring kit and round up some carb cleaning supplies as per the tutorial. Set a side a weekend and get her done!



While you have the carbs off change your manifold (boots) o-ring s as well since leaking here is a known problem affecting carb operation. Robert has those too. One word of caution. Getting the screws on the boots out is a bear and easy to mess up (broken screw heads) so before you go to it read some of the threads on the subject and get yourself an impact driver if you don't already have one.

The carb cleaning and rebuilding does look intimidating but if you follow the excellent tutorial, you won't get lost and it will all turn out. Just be methodical and keep track of your parts as you go. Valve adjustment also looks like a pain but is relatively straight forward and necessary so don't skip it.

You could try one project at a time and if so do the valves first as it may just be the thing to get things working right again. Check some of the threads on this subject as there is a lot of info there too.

Good luck with your maintenace chores.
Cheers,
Spyug.