Throttle does not snap back [Urgent :/]

I recently replaced the airbox to carb boots on my 1981 kz550 ltd. After replacing them and reinstalling the carbs I noticed that the throttle did not snap shut. As in when i let go of the throttle it does not snap back and it sticks in whatever position i put it in. I thought that it would be okay to ride without the throttle snapping shut, however even when the bike is running and I close the throttle, it takes maybe around 5 seconds for the revs to even begin coming back down. Maybe this is an entire problem on it's own? I'm not sure.

I correctly adjusted them and i did lubricate them. There are no kinks and they both operate smoothly. I then started guessing that this could be a bad return spring, however looking back to when I had the carbs on the bench, it was quite hard to remove the spring because of how strong it was, so i'm really not sure on that front either.

I'm really really stuck and i've already spent around 10 hours working on the thing today and i spent the other 2 looking online trying to find a solution. I've been thinking about if its possible to somehow bypass the return cable at all? I know it's a safety measure but i need the bike soon for work, and I'm wondering if that's a legitimate temporary solution. Any and all help is appreciated, thank you guys and stay safe

sorry if this is in the wrong discussion category.

Interesting problem...

You might check for air leaks as they will cause a hanging throttle.

Are you able to confirm the carbs snap shut? You said they were smooth moving so I think thats a yes.

The cable might be getting caught up if you accidently got it pinched somewhere when putting it back together.

Does the hand throttle snap back? If the cable is getting pinched the hand throttle might still return, but the cable would stay in the open position.

I haven't had this problem, but just what comes to mind first.

The carbs are closing fully, i calibrated and set them all to factory specs via the manual before i re-installed them. I was having air leaks before which is why i installed new boots, no leaks that i could tell. And the hand throttle doesn't close at all I'm wondering if maybe the air adjustment screw might change something? Not sure yet

I think you have to have your return spring connected and functional . As it returns your carbs to being fully closed after release of the throttle. If you have a push-pull cable set up. That set up must be adjusted correctly, or it could effect the function of that return spring. Have patients and happy wrenching to all.

If the hand throttle is not closing at all, and the carb slides are closing, then there is a problem with cable adjustment, or with how the cables are hooked up.

Are you sure that the cable ends are fully seated in the fhrottle housing and on the carbs?

Are you sure that the cable outer sheath is fully seated at both ends? It is easy for the sheath to get a bit cocked as it goes into the holder on the carbs. That can prevent the slides from closing.

i thought the same but they are, when i took them apart on the handlebar stem (if that makes sense) to lubricate them they were seated and i made sure they were when i closed them back up. They're visible on the carbs and they're connected too. I was twisting the throttle with them not connected to make sure there was no kinks etc and they were very very smooth.

If you twist the throttle and let go the slides should close with a resounding clunk. If your's are doing that then it sounds like you have a hanging idle due to an air leak. I'd replace the rubber carb boots first and then do a carb sync.

I think i might have worded my question poorly. When i said that the throttle was not snaping closed i meant that the hand throttle is not returning back (ie snapping shut) when I let go of the throttle. Sorry for any confusion.

There are quite a few things that can cause the symptom you describe. My first guess would be cable adjustments or routing, or cable ends not seating where they should.

First thing is to disconnect the cables from the carbs and see if the throttle bellcrank snaps back after opening it by hand.

I run the 550's without the return cable as it always seemed to be sluggish on return. So you could try running just the opening cable.

Pretty sure your cables are too tight. Loosen them up at the carb and it should snap back.

Check that the clamps on the carb boots aren't catching on the throttle linkage. Had that problem once when I had the clamp screws turned up too far (for easier access).

I understand from your description above that your throttle control works when you open the throttle but that you have to manually twist it closed. To me this suggests the problem is with the spring that closes the carb slides. It may be sticking on something or it may not be correctly attached, and the slides may be slow to close, which is indicated by the lag in response time that you mentioned.

However the lag in response time may also be due to air getting into the engine around the carb boots on the intake manifold. If your clamps are not tight you will have air getting into the engine this way. You can check by idling the engine and spraying a little WD40 around the connection between the carbs and the manifold. If the engine revs drop it is a sign that air is getting into the engine but the WD40 made a temporary seal.

You should check your spring action first. Then, if the response time is still poor you should check your intake boots.