plug color and fuel/air screw

[first timer]

I just rebuilt the carbs, synced them, replaced the intake boots, and plugs. The bike works great but the only thing that concerns me is, I'm not able to get the bike to idle below 1800 for any consistent time. It will go to 2k or slowly work its way down to 900 then die out slowly. Other then that I get really good throttle response and power the whole rpm range. I pulled the plugs and they have a little grayish color on the little metal contact but the porcelain is still looking brand new after about 60 miles of ride time. SO my question is: Are my fuel/air screws (the little needles on top you turn about 2.5 times) to open or to closed. I have them turned about 3 to 3.25 times counter clock wise which is suppose to give my more gas right? If so why are the plugs looking to lean? And is this the reason my bike will not idle consistently at 1800 or lower rpms. I've tried the screws at 2.5 turns and there was no difference, unless I needed to run the bike longer at that setting.
Thanks,

 

[Anonymous]

bet you have an air leak

 

[KrazyKarl02]

Might be an air leak, or the worst news is maybe just an old engine . I would also maybe check the cam chain tensioner and all around timing.

 

[first timer]

did that the cam chain is on target and tight, the motor only has 1700 miles on it.

 

[Jay B]

That plug color means its running lean. Also check your air cleaner. If its dirty it will cause the bad idle problem.

 

[Anonymous]

Too much air!

Too much air!

SO my question is: Are my fuel/air screws (the little needles on top you turn about 2.5 times) to open or to closed. I have them turned about 3 to 3.25 times counter clock wise which is suppose to give my more gas right? If so why are the plugs looking to lean?

This seems way too much. On my gs750e it's supposed to be 1+1/2 turns to begin with, not 3. My machine works fine and I have 1+1/4 turns. I had about the same problem with my idle before, and it was solved when I gave the pilots a little more gas (screw the pilot downwards, clockwise) compared to the 2, 2+1/2 turns it was set on when I bought the machine.


/ Henrik

 

[gs650gt]

Re: plug color and fuel/air screw

I just rebuilt the carbs, synced them, replaced the intake boots, and plugs. The bike works great but the only thing that concerns me is, I'm not able to get the bike to idle below 1800 for any consistent time. It will go to 2k or slowly work its way down to 900 then die out slowly. Other then that I get really good throttle response and power the whole rpm range. I pulled the plugs and they have a little grayish color on the little metal contact but the porcelain is still looking brand new after about 60 miles of ride time. SO my question is: Are my fuel/air screws (the little needles on top you turn about 2.5 times) to open or to closed. I have them turned about 3 to 3.25 times counter clock wise which is suppose to give my more gas right? If so why are the plugs looking to lean? And is this the reason my bike will not idle consistently at 1800 or lower rpms. I've tried the screws at 2.5 turns and there was no difference, unless I needed to run the bike longer at that setting.
Thanks,

just checking a couple of things that were't mentioned in Your message:

- do You have sufficient play in the throttle and choke cable?
- does the idle adjusting screw have any influence on RPM?

 

[Anonymous]

3 turns out seems a bit much for the air screws. The norm is about 1.5 turns. That's what the screws on my 650 are set to and it runs and idles fine.

Also make sure there's no air leaks around those intake boots or in the airbox. My bike also ran fine but couldn't idle when I drove off and forgot to tighten up the intake boot clips. :roll:

 

[earlfor]

Re: plug color and fuel/air screw

On my GS750E, the pilot (fuel screw) is set at 1 1/4 turn out. The air screw is set at 2 turns out. It idles just fine at about 900-1000 rpm. It will not idle at all before it is warmed up, but that is normal.

Earl

I just rebuilt the carbs, synced them, replaced the intake boots, and plugs. The bike works great but the only thing that concerns me is, I'm not able to get the bike to idle

 

[first timer]

Yes my throttle and choke cables have enough slack so they should not effect the carb idling, and the idle adjusting screw will either kick it up to 2000 or let it slowly die but can't get it to hit a constant 900 like I want. Also let me get this straight when I turn the pilot clock wise (downward) I increase the amount of gas going in to the carbs, the carb rebuild sez the opposite. So can you please clear that up also?
Thanks,

 

[earlfor]

The pilot is a fuel metering screw, turning it out opens the passageway and flows more fuel (richens). Turning the air screw out increases the air flow which LEANS the mixture.

Earl

Yes my throttle and choke cables have enough slack so they should not effect the carb idling, and the idle adjusting screw will either kick it up to 2000 or let it slowly die but can't get it to hit a constant 900 like I want. Also let me get this straight when I turn the pilot clock wise (downward) I increase the amount of gas going in to the carbs, the carb rebuild sez the opposite. So can you please clear that up also?
Thanks,

 

[first timer]

I re evaluating the carb rebuild article so I get my terminology right. My air screw is turned 3 turns out and my pilot screw (#43 in the carb article) is turned all the way in like it was before i rebuilt it. So my questions are do I need to readjust my pilot screw like earl sez or do I just turn my air screw down to let less air in?

 

[Anonymous]

You have to determine if you have a pilot screw or an air screw. If it's a pilot, also called low speed fuel mixture screw, it will be located in front of the slide, either on top or bottom of the carb. Air mixture screws are located behind the slide, at the carb intake side. Turning the pilot out richens the mixture, turning the air screw out leans the mixture. If we're talking about an '81 GS550 it probably has a pilot screw and not an air screw, but I'm not certain. Also, don't confuse pilot screw with pilot jet. The pilot JET is located inside the float bowl and has no screw adjustment.
Another thing, you rebuilt the carbs, did you replace the jets with exact same numbers?
Axel

 

[first timer]

I have the same carbs as the in the carb rebuild article, the air screw I?m am referring to, is picture #25 of the article. So if I turn this down then i increase my fuel (making the mix richer) I don't know where or what a pilot jet would be if you can refer to one on the carb article it would be helpful to me. I also cleaned and reused the jets in all the carbs, basically followed the article to a t. I appreciate all this help I guess all these different names get confusing after a while. And also how long would it take to cause serious problems to the engine if I continue to run it lean?

 

[first timer]

I have every thing tightened down from the air box to the carbs, I even turn my air screws (guess that?s what they are called) down so they are now only 1.5 turns up. But it still is running lean and will not idle properly, I put about 3 miles on it when it warmed up but the plugs still look like its running lean. All I can still get from it is 2k or slow death idle rpm. I have no more ideas. Should I try and re sync it one last time now that every thing is tight? And still how bad is it to run a motor when it is running lean?