Topic: How open should slides be on idle (PD46A)?

[michtag]

Hi all,
I have been chasing gremlins on my 1977 CB550K3 and now, after a deep carb clean where I unplugged a couple of bowl breather holes and an overflow tube, the bike starts well (always has) but within 30 seconds from stone cold idles between 4.5 and 5k. When warm, just shoots up there straight away. No binding cables, the idle screw is fully off and the shaft rotates all the way to the "fast idle" screw (which I have not touched). Slides are not getting stuck anywhere.
3K miles tune up done and all the rest as suggested by this and other forums (or is it fora?), so I know it could be a series or a combination of factors that I have on a big list and will get to (it is mostly stock, but has paper air filter and 4 into 1 Delkevic exhaust, so some fine tuning will be needed), however, proceeding by elimination I wanted to check with the experts here that my slides are actually in the right position for idling. To be honest I thought they would much closer than this, but before I take the carbs off again I wanted to ask a wider audience.
The carbs have only been bench synced for now as I don't want to perform a proper vacuum sync at 4k RPM...

Are this simply too wide open for idling, meaning I must have messed up something when reassembling the throttle shaft? I have not taken the slides off their linking arms, so there is no chance that I put those back incorrectly (back to front, that is)

Apologies for the mini images...my usb camera is not the best, but it should give you an idea anyway. This is carb #2 viewed from the air box.
Many thanks for checking this out!!
Michele

[bryanj]

They do look a bit far open, try disconnecting the throttle cables and see what happens, also the choke cable as there is a cam in the mechanism to give you a "fast idle"

[michtag]

They do look a bit far open, try disconnecting the throttle cables and see what happens, also the choke cable as there is a cam in the mechanism to give you a "fast idle"

Thank you bryanj, the cables are loose and the the shaft is fully rotated. The fast idle cam is not engaged (id does come into play only if I pull the choke cable fully)
I am starting to think I may have connected the throttle shaft incorrectly to the bellcrank (if that is the correct word for it) but I really don't know how I could have done that....there is only one way to fasten it, as I see it....

[gtmdriver]

It's very difficult to tell as you're looking at it from the airbox side which is where the throttle slide has a semi-circular cutaway so it looks high.

Looking from the engine side the throttle slide should be barely open on idle.

[michtag]

OK, finally some progress.
I realised that even if I had not touched the "fast idle" screw the PO or indeed the mechanic who attempted to settle this bike a few months ago (attempting, failing and blaming worn-out carb's bushings) could have done that. After my latest deep clean, the carbs breathe much better to the slides can be closed more.
To cut a long story short, I unscrewed the fast idle completely and that pretty much did it.
Now I can use the main idle screw to change idling speed and after warm-up it settles nicely around 1000-1200 rpm (on the tach).
So, this problem solved, I am getting closer, I hope to smoothing out everything else that is either wrong or inconsistent about it (slow return to idle, mostly). I won't bore you with it now, I have plenty of suggestions gathered from reading the forum and a list of things to do and to try, but i will probably post a detailed report at some point to serve as a reference for anybody who found themselves facing the same problems.
For those of you not familiar with PD46A carbs, here's what the "fast idle" screw looks like, viewed from below (bottom of pic is airbox side, top is engine side). It should barely touch a cam on the choke shaft, where the 2 halves meet with the spring mechanism. For now I have retrieved it almost completely, but once I have synced the carbs and settled them properly I will reset this as suggested in the manual.
Thank you for your help!