idle issues cont

[Guest]

hi guys so after taking your advice i changed orings cleaned carbs throughly,as per tutorial, synced butterflys,REINSTALLED started with choke fine pushed choke in abit after a minute blipped throttle revs snapped back to idle no hanging revs great.pushed choke in when warmed up it struggled to idle so adjusted idle to idle at 1000rpm now when i blip throttle revs abit slower returning to idle but not hanging thou,so adjusted idle screw back to initial position so now struggling to idle againl so i screwed out mixture screws from 2.5 to 3 turns to increase revs but no change tryed 3.5 turns still no change im thinking i should see a change!or should i screw them in to lean it out to increase revs ! it seems if i open up butterflys to increase idle my revs returning to idle gets slower.should the engine be able to idle with the butterflys shut! should the valve be infront of th 3 little pilot ports when throttle is closed.the bike gs550l 1982 came with a 4 into 1 exhaust jetting is standard. cheers paul.

 

[Big T]

Ok, cleaned carbs thoroughly,?
Did you follow the carb cleaning tutorial?

Idle issues generally stem from:
Dirty idle circuits in carbs
Bad O rings
Tight valves
Air leaks

Since you give us no idea what bike you're talking about, or what you've done to date, a precise answer is impossible

And, please use some paragraphs and punctuation

 

[Guest]

Ok, cleaned carbs thoroughly,?
Did you follow the carb cleaning tutorial?

Idle issues generally stem from:
Dirty idle circuits in carbs
Bad O rings
Tight valves
Air leaks

Since you give us no idea what bike you're talking about, or what you've done to date, a precise answer is impossible

And, please use some paragraphs and punctuation

dont assume big t that everybody has equal ability to put there thoughts into words on paper regards paul.

 

[steve murdoch]

I think i am seeing that it idled well at one point when warm and you had the idle set at 1000 rpm but that it was slightly slow to return to that idle?
I wouldn't be using the mixture screws to try and adjust the idle.

Big T mentioned a number of causes of erratic idle. I lean towards air leaks.
You have a 4-1 with stock jetting? What airbox/filter are you using?

 

[tom203]

?...should the engine be able to idle with the butterflys shut??

yes, they are just open a sliver.....the little holes in carb throat supply enough mixture to sustain a steady idle.
go back to mixture screws at 2.5 to 3 turns out....with bike fully warmed up (and choke fully turned off) set idle stop screw to give a 1200 rpm idle. Make sure the ?choke? plungers are fully off or you will get an erratic idle when warmed up.

 

[bobtail84]

Can I suggest using a colour tune to set up the idle.

I found that just adjusting the idle screws is pointless unless you are a carburetor jedi, with the colour tune you can see the burn as you adjust the screws and it works a treat. If you do have an air leak the mixture will show you it's lean by the white-ish colour of the spark.

I messed around setting up my 33mm smoothbores for weeks, riding and changing but could not get the idle right, gave up and went to the local motor factors and purchased a Gunson colour tune and no more than an hour later the bike idles fine.

Of course I am hoping you have at least 11v at the coils, the plug gaps are correct, even with a rough idle you have sprayed WD40 or easystart around the carb boots to see if the revs rise, the slides are all at the same hight and the carbs are balanced if that's all done then use the colour tune and away you go, hopefully.

 

[Guest]

I think i am seeing that it idled well at one point when warm and you had the idle set at 1000 rpm but that it was slightly slow to return to that idle?
I wouldn't be using the mixture screws to try and adjust the idle.

Big T mentioned a number of causes of erratic idle. I lean towards air leaks.
You have a 4-1 with stock jetting? What airbox/filter are you using?

hi steve thanks for reply yes it idled with choke slighty on and revs returned sharply back to idle.when i turned choke off it struggled to idle so i adjusted idle to 1000 rpm and yes when throttle was blipped revs were slower to return. IT seemed to me the more i opened up the butterflys the worse the return to idle got. i synced the the carbs on the bench to my to haynes manual which said to set them till you cant see light past them so basically shut!should it be able to idle at this position. yes it has stock air box i will double check for air leaks but havent found one so far thanks for your help and big t i do take on board all advice cheers paul

 

[Guest]

hi tom thanks for reply,if you open up the buttrflys to increase revs, does it not increase chance of hanging revs as you will be allowing the fuel from the 3 little fuel ports to contiue to supply fuel when throttle is shut as butterflys will not be completly closed.!hope you can clear me up on this its just what i got in my head!cheers paul

 

[Guest]

Can I suggest using a colour tune to set up the idle.

I found that just adjusting the idle screws is pointless unless you are a carburetor jedi, with the colour tune you can see the burn as you adjust the screws and it works a treat. If you do have an air leak the mixture will show you it's lean by the white-ish colour of the spark.

I messed around setting up my 33mm smoothbores for weeks, riding and changing but could not get the idle right, gave up and went to the local motor factors and purchased a Gunson colour tune and no more than an hour later the bike idles fine.

Of course I am hoping you have at least 11v at the coils, the plug gaps are correct, even with a rough idle you have sprayed WD40 or easystart around the carb boots to see if the revs rise, the slides are all at the same hight and the carbs are balanced if that's all done then use the colour tune and away you go, hopefully.

i will check these pionts bob, im almost there compared to what it was rev s were hanging bad a week ago but not to much now. thanks for info cheers paul.

 

[Guest]

hi guys so went round to dads today started bike up with choke on and butterflys closed idled fine pushed choke in bike wont idle but revs out good,good throttle response and revs come down nice but just wont idle.i turned idle screw to get it to idle at 1000rpm sprayed carb cleaner all around jionts boots etc no change in engine tone i cant find air, leak,blip throttle now and revs hang. if there was a air leak wouldnt it effect the revs when butterflys are closed and i rev it!.if it should idle with butterflys closed then is this pointing to a pilot circuit issue cheers paul.

 

[gustovh]

You might want to try this. Starting with the #1 carb, slowly turn in the pilot screw, one of two things will happen, the revs will either fall or climb. If they climb continue turning the screw in until the revs fall then back it out about 1/4 turn. You may have to reset the idle down, then move on to the #2 carb and repeat until all carbs have been adjusted. It may take a couple goes to get them right.

You may have to set the idle up to start. Have you performed a vacuum sync first to match carbs first. The above process is called lean best idle adjustment. Hope this helps.

V

 

[Guest]

hi gustov no i havent done a vacuum sync yet im assumming it should run somewhere near before hand, ive done a bench sync, am i wrong in thinking this!. i will do as you suggest with the mixture screws tomorrow and let you know results. Can you confirm if the engine should idle with butterflys closed without choke on!because if it should im thinking have a problem with fuel supply in pilot circuit, what do you think!, cheers paul

 

[zed1015]

Can you confirm if the engine should idle with butterflys closed without choke on!because if it should im thinking have a problem with fuel supply in pilot circuit, what do you think!, cheers paul

The throttle butterflies on CV carbs control the air flow through the venturi leading to fuel pick up and hence the throttle and idle.
The bike cannot idle with them fully closed as there would be no flow of air.

 

[gustovh]

hi gustov no i havent done a vacuum sync yet im assumming it should run somewhere near before hand, ive done a bench sync, am i wrong in thinking this!. i will do as you suggest with the mixture screws tomorrow and let you know results. Can you confirm if the engine should idle with butterflys closed without choke on!because if it should im thinking have a problem with fuel supply in pilot circuit, what do you think!, cheers paul

A bench sync can get you close and running, sometimes plenty good enough. I believe that the pilot circuit is too fat in your case and that the butterflies are not your problem. If the lean best does not do it for you...time to pull and go through the carbs again. Do not forget to use a big fan on the engine while running it and making adjustment.

V

 

[Guest]

idle issues

idle issues

The throttle butterflies on CV carbs control the air flow through the venturi leading to fuel pick up and hence the throttle and idle.
The bike cannot idle with them fully closed as there would be no flow of air.

hi zed thanks for reply im not sure thou because the haynes manuel says to set butterflies till you cant see no light past them this is virtually closed but obviously there not a perfect seal so some air will get through plus you have the suction from the engine pulling fuel !it does seem to idle on choke with butterflies closed but not without choke! i dont know i can see where your coming from too, i im getting really frustrated i appreciate your help thou, today i noticed no4 cylinder not firing checked out plug cap, lead ,coil etc there not the culprits so gonna do comprresion test and pull carbs of again, cheers paul.

 

[Guest]

A bench sync can get you close and running, sometimes plenty good enough. I believe that the pilot circuit is too fat in your case and that the butterflies are not your problem. If the lean best does not do it for you...time to pull and go through the carbs again. Do not forget to use a big fan on the engine while running it and making adjustment.

V

hi gustov didnt get to play with mixture screws to day found another issue cylinder 4 not firing!! checked out leads ,plug cap coil, thjey are good as i swapped them with no 1 cylinder issue didnt move to that cylinder.so yeah gonna pull carbs off again they have been in the bath twice already and i have blown carb cleaner through ports/holes blown it through with comppresed air ,but how do you gauge there completely unblocked and clean unless you have a comparison! im gonna do a compression test on cylinders tommorrow,what is the minimum psi required i think if i remember no 4 was about 100psi not great but ill check tommorow,cheers paul.

 

[gustovh]

hi gustov didnt get to play with mixture screws to day found another issue cylinder 4 not firing!! checked out leads ,plug cap coil, thjey are good as i swapped them with no 1 cylinder issue didnt move to that cylinder.so yeah gonna pull carbs off again they have been in the bath twice already and i have blown carb cleaner through ports/holes blown it through with comppresed air ,but how do you gauge there completely unblocked and clean unless you have a comparison! im gonna do a compression test on cylinders tommorrow,what is the minimum psi required i think if i remember no 4 was about 100psi not great but ill check tommorow,cheers paul.

I believe 100psi is low service limit. So it looks like you need to go through the whole process starting with a valve adjustment, carb clean and don’t forget to change the “0” rings behind the carb mounts. I would also remove the plug caps and cut about 1/4” off the end of the wires and then screw them back on.

#3 carb is not adjustable so the other carbs are adjusted to it. That said, this is how I bench sync my carbs. Using 2 pins of the same dia. I use 1/8” drills I place the end of 1 drill under the butterfly on #3 and make sure that it is centered, you now have a 1/8” gap. Using the end of the other drill I set the gap in the other 3 carbs, there should be just a tiny bit of resistance to the drill. That should get you very close.

V

 

[salty_monk]

You can get leaks at the airbox as well as the intake boots. They would bypass the filter. You need to make sure you have a good seal to the carbs, that the doors on both sides are well sealed, that the foam filter is oiled properly & that the filter cage is sealing to the airbox body properly.... if not then time for new airbox boots & get some foam draught excluder to use as a seal material for the cage & doors.

 

[Guest]

hi gustov so are you saying that after you finish sync that when your throttle is closed with 1/8" gap that is how you leave it set up for idle!yes were gonna check the valves my dad says their fine but i want to check them other wise i just feel like im going round in circles,i have replaced orings ,set floats cleaned carbs, gonna check the plug gaps too to make sure, like i said previous how do you know for sure every little passageway in carb is completly unblocked but i am going to pull them off again. cheers paul.

 

[Guest]

hi salty i will make sure this is the case when i put it back together again! think my dad should of stuck to his old british bikes ,singles and twins twice the issues with four cyl;inders lol,i just want to get it sorted for him hes 80 yrs old, he wanted another project ,oh well hope we get there in the end with it thanks for your help cheers paul.