adding a little choke

[Guest]

hey everyone, I've been trying to tune my 83 gs 750. its been a long road and I'm making progress. if I'm crusing say 4000rpm I feel a slight I guess you would call it surging but real slight, but if I add a little choke I can feel that it clears up. seems like it might run just a bit smoother at all rpms if I crack the choke just a bit. Bike starts perfect idles great and wot pulls strong. Why am I having to apply choke? Any advice is apricated! Thanks Andy

[chuck hahn]

Its lean and adding some choke richens it up and it goes away. Turn the mixture screws ( top rear of the carb throats ) out 1/4 turn more and see how it does then.

And as stated in the other reply..get some ether and start the bike. spray ether on each carb intake manifold and listen for a rise in RPMs. This will indicate a vacuum leak resulting in a lean condition as well.

[tkent02]

It's lean all right, but find out why. Tuning a mixture screw to bandaid fix an air leak will work for a while, but will only get leaner later when the leak gets bigger. Running lean will burn holes in pistons, you don't want to risk that. Take it apart and find out what it needs to fix it right.

[chuck hahn]

Cracked up intakes and leaking intake orings are bad news. Heres a little explanation of the importance of good intake orings.

http://cycleorings.com/intake.html

[gsrick]

Its lean and adding some choke richens it up and it goes away. Turn the mixture screws ( top rear of the carb throats ) out 1/4 turn more and see how it does then.

Chuck he says it idles good, wouldn't raising the jet needle a clip or two provide more fuel needed at 4000 RPM?

[chuck hahn]

I was typing another post as you and Ed chimed in.......and not until he has eliminated intake leaks would he start with any needle raising or jet changes. But i think its probably a leak.

Original poster..how far out from GENTLY seated are the mixture screws right now?? Conventional trial and error wisdom around here says 2 to 2 1/2 out is pretty good.

[helmutholderbenz]

HEY, Thanks guys for the input. Lets start with the air leak issue. I don't think thats the problem. I did buy some second hand boots off ebay but on inspection they were very good and still very plyable, way better than the ones I replaced. I installed new orings as well. I did spray them down with wd40 while the enging was running to check for leaks and noticed no difference in rpm. I also want to say that the bike starts like its supposed to, First start of the day I apply choke, no throttle, boom, starts right up. let it warm up a minute take off choke and a rock solid idle, blip the throttle and it returns right back to its 1100 idle. that part seems perfect.

[chuck hahn]

So you have to richen it up. Where are the mixture screws set at? Whats the air filtering setup...pods or stock?? What groove on the jet needles is the E circlips on? Got any pinholes in any of the diaprams and are they seated in the grooves right..not pinched under a cover?? Are you sure the clamps arent stretched? Stretched clamps will not seal good and cause problems. Just a few things I would be checking if i was working on it.

[helmutholderbenz]

Chuck he says it idles good, wouldn't raising the jet needle a clip or two provide more fuel needed at 4000 RPM?

This is what I'v been thinking!!! my bike has the cv/bs32ss carb set up and they dont have the adjustable needles. just for that reason I want to get the Dynojet 3 jit. But I think I might have fuel level problems.

[helmutholderbenz]

So you have to richen it up. Where are the mixture screws set at? Whats the air filtering setup...pods or stock?? What groove on the jet needles is the E circlips on? Got any pinholes in any of the diaprams and are they seated in the grooves right..not pinched under a cover?? Are you sure the clamps arent stretched? Stretched clamps will not seal good and cause problems. Just a few things I would be checking if i was working on it.

let me answer some of these questions. My clamps are good, when I tighten them there is still room to tighten more. Im running ape pods with kn oil. Ive checked and rechecked for pin holes in diaphrams and they are good and they are plyable, I always take good care to make sure they are in notches when I put them in. I've been fooling with float level and that really makes a difference. I have the mixture screws at 3 out right now and i've been leaving them at that setting for a few adjustments now cos the bike idles so good. when I do adjest them they are very sensitive 1/8 turns make a difference. i'm useing mikuni 130 mains, started with 140s and worked my way down and haye been concidering trying 127s cos I still get a little bog at wot.

[helmutholderbenz]

If my fuel level is too low will my bike run lean?

[helmutholderbenz]

one more thing I feel needs to be mentioned is after a ride my tail pipe is sooted up! how can this be? i feel like I have a lean problem but the tail pipe gets all black!

[tkent02]

If my fuel level is too low will my bike run lean?

Yes.

one more thing I feel needs to be mentioned is after a ride my tail pipe is sooted up! how can this be? i feel like I have a lean problem but the tail pipe gets all black!

Might be so lean it's misfiring, or might be lean on some circuits and rich on others. It really shouldn't be a guessing game, get in there and find out what's happening.

[Steve]

one more thing I feel needs to be mentioned is after a ride my tail pipe is sooted up! how can this be? i feel like I have a lean problem but the tail pipe gets all black!

Seems to me that I remember you mentioning you are using the "choke" while riding?

The "choke" is actually an enrichening circuit, which richens the mixture for STARTING, not for running.

.

[chuck hahn]

You can shim the jet needles by adding thin ( .005 thick ) washers under the circlips. Someone here can tell you more about where they get thiers. By raising the needles your richening it just a tad so a few shims may take care of the stumble.

Ive been lucky in that I havent ran pods and all my bikes have stock airboxes, but i have read many a thread about shimming the needles. Maybe use the search feature and use keywords such as shimming needles for some threads.