idle issues

[bean1969]

hi members this is my first post as new to site,my dad bought a gs550l 1982 and has done it up he is pretty good on 4 strokes but mainly worked on older british bikes . the bike starts up fine and idles we have noticed one cylinder 4 not firing correctly, thou there is a spark .when i rev the bike up to 3000rpm approx it hangs there when throttle is shut or sometimes comes back down to idle slowly,would the no4 cylinder not firing correct be the reason the revs not coming down to idle when throttle shut.he is going to take carbs off again and check no4 carb,i have sprayed carb cleaner around boots when idleing to see if there is any air leaks but engine revs didnt alter.compression acoss cylinders is 100psi any advice please would be welcome thanks paul.

[Rich82GS750TZ]

Did you check free movement of the throttle cable and that the throttle linkage snaps back closed at the front of the carbs when the throttle is released?

[Big T]

Bean,

Hanging idle is air leaks
Carbs cleaned per tutorial?
Valve clearances checked and correct?
New O rings behind carb boots?

[zed1015]

Also check choke plunger seats as one or more of these leaking fuel will cause a rich mix on it's associated cylinder and a hanging idle etc.

[bean1969]

idle issues

Did you check free movement of the throttle cable and that the throttle linkage snaps back closed at the front of the carbs when the throttle is released?

hi thanks for reply yes its snapping back good they have a good spring there thats for sure really want to get it right for him he 80 years of age and had a lot of problems with it and he doesnt have the health these days to spend alot of time on it so im trying to help but im more of a 2 stroke man he has had all the top end apart new piston rings reseated valves assures me the clearences are correct, he has had carbs apart a few times to clean, i think he is thinking of taking them off again ,cheers paul.

[bean1969]

idle issues

Bean,

Hanging idle is air leaks
Carbs cleaned per tutorial?
Valve clearances checked and correct?
New O rings behind carb boots?

hi is there carb tutorial on this site! no he hasnt replaced orings he told me they were fine,and he said hes set the valve clearence as per manual when im with him next i will check orings and make sure all boots are snug ,when it starts with no throttle it idles at 1000rpm approx i sprayed carb cleaner round boots but no change in revs,it hangs when i blip the throttle then slowly returns to 1000rpm, but cylinder 4 isnt firing correctly so going to check leads out tomorrow to rule out electrical issue thanks for reply regards paul.

[bean1969]

hi there i will tell my dad to check or i will for this cheers paul

[tom203]

Remove spark plug boots and snip about 10mm off each plug lead....this will ensure fresh copper and good connection.
since you are taking carbs off, change carb boot o-rings ..even if they look ok. Make sure you use viton ones.

[Rich82GS750TZ]

Being an ‘82, can I assume CV carbs? 2 excellent carb cleaning/rebuild tutorials and a lot of other great GS related stuff on BikeCliffs website, link in my Signature. Carb stuff is at the top of the right hand margin on the page.

[bean1969]

yes ok i will do that with leads also going to swap 1 and4 cylinder leads to see if issue moves to cylinder 1 i will tell him top get new orings i might have some viton ones at work ill see thanks for reply ,

[bean1969]

hi yes they are cv carbs just had a quick look at that site and carb cleaning looks good i will show my dad this and assit him with the help of this guide thankd paul.