Idle / carb issues

[MilesDad]

I just THOROUGHLY cleaned my carbs and added a stage 1 dynojet kit.
It is starting fine, and runs fine for the most part (haven't driven it yet).

Here are the issues I have.
It will idle around 2k RPM, but if I adjust the idle knob to try to make it idle near 1k RPM, it "conks out" as my wife says.

I put a manometer on it and adjusted a bit to get them synced when running at about 2k RPM.

The idle issue paired with the jumpy manometer readings lead me to believe I may have a vacuum leak. My boots are in good condition, though not new.

See videos here: http://www.youtube.com/user/MYOOTOOBabc123?feature=mhee

Your input is appreciated. I can't wait to get this thing running better so I can ride it. This rebuild has been a long and enjoyable process.

 

[Guest]

I just THOROUGHLY cleaned my carbs and added a stage 1 dynojet kit.
It is starting fine, and runs fine for the most part (haven't driven it yet).

Here are the issues I have.
It will idle around 2k RPM, but if I adjust the idle knob to try to make it idle near 1k RPM, it "conks out" as my wife says.

I put a manometer on it and adjusted a bit to get them synced when running at about 2k RPM.

The idle issue paired with the jumpy manometer readings lead me to believe I may have a vacuum leak. My boots are in good condition, though are not new.

I have never been able to dial my idle in either. I can set it at 2000 rpm but can't lock in it at 1000rpm, just dies out. I have new boot & rings and complete carb cleaning. I am at a loss. Hope others chime in...good luck

 

[hampshirehog]

It's running very weak. So you need to check for an air leak - intake rubbers, airbox rubbers, airbox lid, vacuum hose etc. If they're ok you need to make sure that your mixture screws are out about 2 - 3 turns and set the idle using the highest revs procedure.

Why have you put on a Dyno kit by the way and was it running ok beforehand?

 

[MilesDad]

It was running worse before I worked on it - it had to have constant choke to stay running. I put the stage 1 dynojet because I put Vance and Hines 4-1 pipes on it. The original ones were rusted out.
I'll re-set my mixture screws, as they are at about 1-1/4 turns out as of now.

I didn't think it mattered, but maybe you have found an issue. I have the stock air box setup. The air box with the filter in it is not sealed. The lid has big gaps in it.
The box between the filter box and the carbs seems to be well sealed.

I sprayed WD-40 on my intake boots, and my engine revs did not change a bit. They seem to be fine.
Your note that it is running weak makes sense, but once at 2000 RPMs and higher, it is strong and responsive.

Is the filter box (housing) needing to be sealed? I wouldn't have guessed it. Any other thoughts?

It's running very weak. So you need to check for an air leak - intake rubbers, airbox rubbers, airbox lid, vacuum hose etc. If they're ok you need to make sure that your mixture screws are out about 2 - 3 turns and set the idle using the highest revs procedure.

Why have you put on a Dyno kit by the way and was it running ok beforehand?

 

[Gonzo]

It was running worse before I worked on it - it had to have constant choke to stay running. I put the stage 1 dynojet because I put Vance and Hines 4-1 pipes on it. The original ones were rusted out.
I'll re-set my mixture screws, as they are at about 1-1/4 turns out as of now.

I didn't think it mattered, but maybe you have found an issue. I have the stock air box setup. The air box with the filter in it is not sealed. The lid has big gaps in it.
The box between the filter box and the carbs seems to be well sealed.

I sprayed WD-40 on my intake boots, and my engine revs did not change a bit. They seem to be fine.
Your note that it is running weak makes sense, but once at 2000 RPMs and higher, it is strong and responsive.

Is the filter box (housing) needing to be sealed? I wouldn't have guessed it. Any other thoughts?

I'd seal that box if only to rule that out. It's simple and quick enough to do, and hey, it just might solve the issue.

 

[Guest]

Let me know what happens with it. I am about ready to pull my carb bank off again and inspect the idle screw and see if maybe the spring is weak or something. I may also order a new throttle cable just to eliminate that too although mine appears to work fine.

 

[almarconi]

You don't say what bike you are working on. If it has CV carbs, 1-1/4 turns on the mixture screws is too lean. I've got mine (BS32's) at 3 turns out with stock exhaust and airbox. Typically you should bench sync the carbs first. Then set the idle on each carb using the highest idle method or a colortune. Finally sync the carbs with a manometer. If you put your bike in your signature it will be easier to help you out.

 

[elrico]

Mr.MilesDad,hi.Did your DJ Stg.1 kit have maybe (happens) missing info. sheets? even w/all info,sheets etc.wordages/and instructions at times conflict abit.I have Stg. 1 kit still in package/Box,am warming up to maybe do spare/back up carb set in future.Sorry (Off point). Q:was 'Troubleshooting Guide"found with your kit/box?If misplaced/missing,is most important to have,of course again ,all pertinent sheets.for certain. Dynojet 1 800 992 4993 or dotcom.

 

[koolaid_kid]

The bike (who knows what it is?) has an 85 mph speedo. That means it has CV carbs. An air box lid that does not seal is considered an air leak. You must seal it or it will not idle w/o the choke. Don't ask me how I know.

 

[MilesDad]

Okay friends, in my haste I did not mention what bike I have. I apologize for that. I have a 1981 GS750E.

I think I have this thing solved.
Steps I took included:
-I replaced the vacuum tube from the petcock to the carbs. I don't think that had anything to do with it, but I had tubing, so I changed it.

-I did have an air leak where the filter box connects to the air box, as evidenced by RPM surging after spraying wd40 on it. That may have had some effect, but after I got it idling fine, it'd even idle fine without the filter box connected. That said, sealing the cover of the filter box seemed to have no impact on my particular idling issue.

The two biggest factors, based on my tuning today were:
1. Turning the mixture screws out 2.5 turns. That made a substantial difference. I just couldn't find a setting online, so I wasn't sure how to set them. Thanks for the suggestion.
2. Re-adjusting the throttle cable so the idle knob actually controlled the idle. My cable seems to have been a tad tight, and I mean just a little. I think my idle getting down to 1000 RPM and then dying was the result of poor fuel mixture, not true idle adjustment.

That's that, I think. It seems to be running like a champ, though I still need to get it out on the road. RPMs don't hang when I blip or rev up the engine, and throttle seems quite responsive, as I had hoped it'd be.

Thanks to everyone who offered assistance. Let me know if you have any questions that will clarify something or help someone. I'll sure try.

 

[hampshirehog]

The 2.5 turns out will get you close to a decent setting but you can easily set it spot on. All you have to do is turn the mixture screws in or out and listen to the engine note - you'll hear the revs pick up / fall away (turn the screw slowly). When you have the highest idle you have set the mixture screw right for that carb - move on and do the other 3.

 

[MilesDad]

Yep, the highest idle method is what I'll use to get it as right as I can.
I appreciate your help.

The 2.5 turns out will get you close to a decent setting but you can easily set it spot on. All you have to do is turn the mixture screws in or out and listen to the engine note - you'll hear the revs pick up / fall away (turn the screw slowly). When you have the highest idle you have set the mixture screw right for that carb - move on and do the other 3.