crazy idle

My 78 1000a likes to idle high sometimes its bad when she warms up.I checked for vac leaks found 0 I can let the clutch out out a little and it go's back normal but have to start in first gear after motor is warm.Its hard on the shifting with a problem like this..

I wonder if you may have a tear in the diaphragm (rubber suspension) around the carburetor piston?

bountyhunter wrote:

I wonder if you may have a tear in the diaphragm (rubber suspension) around the carburetor piston?

i thought 78 still had manual slide carbs.

i would check the air screws on the carbs, someone may have tried to sync the carbs and back out the air screws too far out.

I checked screws about 1 whole turn out, the carbs are 29 smoothbores plus my main idle adjustment screw is all the way out should I turn all screws in and main about half and start from there

they dont sound too far backed out. give it a shot i'm not a expert at carbs but when i had issue with my 26mm's i grabbed a manual and made sure my slides were open to spec for "closed" throttle and then backed out the air screws to static sync. then i tinkered with each airscrew and listened to each cylinder with a stethoscope till they all sounded similar. It's not the greatest way to sync them but i couldnt find my vacuum gauge

Air/pilot screw has nothing to do with carb synchronizing!

Synchronizing carbs means that you adjust the amount of vacuum in all carbs to same level (to which level is pretty much insignificant). This is done by adjusting THROTTLE BODY BUTTERFLY VALVES and nothing else.

Click: www.carbtune.co.uk/carboprn.html

I really mean no offence by writing so pluntly here but this is a pretty common misunderstanding and even today I´ve read this same misleading advise about synching twice.

Z1109R Fin wrote:

Air/pilot screw has nothing to do with carb synchronizing!

Synchronizing carbs means that you adjust the amount of vacuum in all carbs to same level (to which level is pretty much insignificant). This is done by adjusting THROTTLE BODY BUTTERFLY VALVES and nothing else.

Click: www.carbtune.co.uk/carboprn.html

I really mean no offence by writing so pluntly here but this is a pretty common misunderstanding and even today I´ve read this same misleading advise about synching twice.

Air/fuel -screw is used to adjust the mixture from idle up to 1/4 throttle.

Idle screw is used to adjust the level of idle and has nothing to do with mixture. It´s just a manual thingy to adjust how far down the throttle linkage can go.

Sorry:blush: I meant to edit not quote my post...

On my 82 GPZ 750 I finally cured it by routing the thottle cable a different way after it driving me nuts

Z1109R Fin wrote, "Air/pilot screw has nothing to do with carb synchronizing!"

Uh oh... we are going to disagree here. If the air fuel mixture is way off, the bike will run so poorly that the carb sync is impossible. I suggest that the idle air/fuel mixture be adjusted prior to synchronizing.

There is no real way to know how to answer this problem due to the lack of info provided... Does the idle HANG and take a while to come back down or is it erratic... shoot up high when you are idling on a random basis?

And folks, there are no throttle butterfly valves or slide diaphragms on these carburetors. The reason that the idle adjust screw isn't touching the stop and the bike idles too high is that a proper bench sync was not done. The bench sync puts the slides in the middle of the adjustment range of the screw... in other words the slides will open and close where they should.

mtkawboy mentioned throttle cable... that is always a possibility with idle issues. If the cables is mis-routed or binding, the idle will be messed up. If the throttle is riding on a bed of old rust up under the right switch gear, binding will occur as well. Taking off your throttle sleeve every now and again and cleaning and geasing the bar end makes a lot of sense.

wiredgeorge wrote:

Z1109R Fin wrote, "Air/pilot screw has nothing to do with carb synchronizing!"

Uh oh... we are going to disagree here. If the air fuel mixture is way off, the bike will run so poorly that the carb sync is impossible. I suggest that the idle air/fuel mixture be adjusted prior to synchronizing.

There is no real way to know how to answer this problem due to the lack of info provided... Does the idle HANG and take a while to come back down or is it erratic... shoot up high when you are idling on a random basis?

And folks, there are no throttle butterfly valves or slide diaphragms on these carburetors. The reason that the idle adjust screw isn't touching the stop and the bike idles too high is that a proper bench sync was not done. The bench sync puts the slides in the middle of the adjustment range of the screw... in other words the slides will open and close where they should.

mtkawboy mentioned throttle cable... that is always a possibility with idle issues. If the cables is mis-routed or binding, the idle will be messed up. If the throttle is riding on a bed of old rust up under the right switch gear, binding will occur as well. Taking off your throttle sleeve every now and again and cleaning and geasing the bar end makes a lot of sense.

WG, I´m no way trying to be a wiseguy or a guru here but...Sychronizing as a term means balancing the vacuum that either butterfly valves or manual slides create inside the carb venturi. Vacuum must be even in order to suck even amount of fuel in to all cylinders. This is why I wanted to make clear what syching means. All other adjustements like air/fuel, needle position, jetting are related to mixture adjustement.

Of course carbs should be on the bal park before you can start adjusting them in any ways. Therefore bench-sync is #1 in work order, then basic jetting to get the bike running and then you should sych them and stert finding best jetting.

My experience in carbs is some what limited. I got (bike is ´83 ELR) my BS34´s running pretty nice after 998->1109cc bore, mild porting, K&N pods, 4-1 open exhaust and so on. Then I bought TM33 flat-slides (off a GSXR), dyna coils and some other bits and pieces and again got them running pretty well. Actually last winter bought a A/F Ratio meter (bolted on all the time) ang Morgans CarbTune. These two gadgets made a world of difference compared to test-ride-bummer-test-ride-oh-crap -method. This summer it really pulls like a maniac.

I´ve been reading post on KZR for a few years now and would like to see some kind of a basic walk-through to settin up carbs. Now people are asking the same question over and over again which means that those (not me) who really know about these things get really tired to writing here all the time.

Please understand that again this is no offence, KZR and some other forums have been a tremendous help for me.

Ok... You bought an EGA and made two sets of carburetors work... now think that the advice I have given over the years is: test-ride-bummer-test-ride-oh-crap -method ???

I have synchronized THOUSANDS of sets of carburetors and made a statement based on that experience and will stand by it. Making the idle mixture right prior to synchronizing any carburetor is necessary and the closer to correct, the easier it is to sync. I also have an EGA and several very professional sets of sync gauges. They DO NOT make all the difference in the world when tuning; experience does.

When we're new to all this and come to this forum we really don't know how to search nor where to start. That's why, I think, the same questions are asked and answered over and over. I thank the members here who are patient enough to go over the same things again and again. Also, there are those who know how to direct us to the archives where we can do some research. There are basic fundamentals to follow, but, like I already said, a newbie doesn't know where to start! Thanks for all the help we can get here.

"Repetition strengthens and confirms".

P.S. I'm "computer illiterate",too, but I'm still learning.