It won't idle down?

[arveejay]

This one has got me stumped. My 1980 GS850G does not want to idle down properly. I just took it for a ride. Runs great. Parked it to put away till I go to work, put it in neutral, it idled at 2500 rpm for about 15 seconds then fell to about 1100 rpm and idled smooth. It does this each time I ride it, every stop light. stop sign, always. I bought these carbs off ebay, supposedly for an 850, never verified, don't know how. Have not syncd carbs yet, will do this weekend. I can't imagine it would run better than it does now but will sync them anyway. Anybody able to steer me in the right direction as to what it might be. Carbs have been seperated, tore completely down and all openings and are clear and free. New plugs this morning, NGK B8ES at 30 thousanths. As far as I was told all stock jets, stock exhaust, and stock air filter. Thanks in advance. I wont see answers till later this evening.

[Anonymous]

I have the same problem. While I ride if I pull up to a light or stop sign sh revvs about 2000 and I have to blip the throttle to get her to rev down. I am also stumped. I thought it might be because I only have 1 throttle cable hooked up. But the spring is so strong I don't think that's it.

[chuckycheese]

Plugs?

What do your plugs look like?? I think one possibility is that your air mixture screws are set too lean. Pull a couple of plugs and see if they're really white and look dry and "cooked". If so, back out your air mixture screws until they're tan. (start with a half turn..out) If that's the problem, your idle RPM's will drop just as they should.

[earlfor]

When an engine doesnt idle down promptly, it indicates a lean condition in the idle range settings. This lean condition can be caused by cracked induction "O" ring seals. (the "O" rings on the face of the induction tubes between the cylinder head and carb. It also can be caused by incorrect fuel pilot screw and airscrew settings. Usually, the fuel pilot screw will be set around 1 to 1 3/4ths turn out and the idle airscrew will be between 1 1/2 to 2 turns out.
The effect of the two is opposite relative to their settings. Turning the fuel pilot screw out will increase fuel flow and richen mixture. Turning the idle airscrew out will increase air flow and LEAN the mixture.
I would check to see that the fuel pilot and idle air screws are within the
above ranges, and if not adjust them so that they are. If this has no effect, then its a pretty safe bet you need new induction "O" rings. They can be bought at the local dealer for about $1.50 each. The rubber composition of them is very specific, Do not replace them with common auto supply house "O" rings as they will last for only about a half hour. :-)

Earl

[Hotblack]

I believe you can spray starting fluid on your intakes while it's running to see if they're leaking or not - if it affects the engine speed then you have a leak. I've done it on cars anyway, I'm guessing it would work the same way in this situation.

[arveejay]

Thanks guys, I'll check it out. It does have a dif. set of carbs and I'm just starting to ride with them. I currently have the air screws at 1 1/2 turns out. Where are the fuel pilot screws. I didn't even know they existed. I thought everything was bottomed out except the airscrew. I will check the plug colors today. I just put new plugs in yesterday and rode it to work and back, 8 miles. Thanks again for the help.

[arveejay]

According to the color spark plug chart which was so generously given to me right here in this forum the plugs look like a combination of the pics # 19 21 23.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Looks a little lean, correct? Let me know, thanks.

[arveejay]

According to the color spark plug chart which was so generously given to me right here in this forum the plugs look like a combination of the pics # 19 21 23.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Looks a little lean, correct? Let me know, thanks.

[chuckycheese]

air screws

I, too, am confused by Earl's answer (although he sure sounds like he knows what he's talking about). The screw I was referring to was the pilot air screw....but where in the heck are the air mixture screws. The only adjustment that I know of on my carbs is the pilot air screws...(except, of course, the knob that adjusts idle RPM) :roll:

[lhanscom]

:?

[TheNose]

Re: air screws

I, too, am confused by Earl's answer (although he sure sounds like he knows what he's talking about). The screw I was referring to was the pilot air screw....but where in the heck are the air mixture screws. The only adjustment that I know of on my carbs is the pilot air screws...(except, of course, the knob that adjusts idle RPM) :roll:

The fuel pilot screw is on the bottom of the VM type carbs on older bikes. If you have a CV carb like in the picture, then you don't have that adjustment.

Terry

[chuckycheese]

Thanks

Thank you, Terry. I do have the carbs pictured so you've cleared things up!

[earlfor]

Re: air screws

Sorry guys, I didnt realize until now that you were adjusting CV carbs and not the mechanical slide VM type. Cv's dont have an adjustable fuel pilot screw. In a way, that simplifies the problem. Either the pilot is clogged and restricting fuel flow in idle range, or you have a vacum leak. Most likely, the cause is (trust me :-) )intake vacum leaks.

Earl :-)

I, too, am confused by Earl's answer (although he sure sounds like he knows what he's talking about). The screw I was referring to was the pilot air screw....but where in the heck are the air mixture screws. The only adjustment that I know of on my carbs is the pilot air screws...(except, of course, the knob that adjusts idle RPM) :roll:

[Hotblack]

In my manual they caution never to adjust that bottom screw, it can only be set properly at the factory. Is that some kind of 'emissions scare tactic'?

[skip]

before you get too involved in you carbs ,sync them. My carbs are not cv's but every time they wont idle down I sync them and it goes away. It has happened on four different occassions over the years. always check for a vacum leak first like intake boots but dont rule out the carb sync .........it worked for me