Topic: Need help - 77 PD carb Idle Adjustment screw not touching

[dumpster84]

Hey guys, I just replaced all of my internals from a leaky set of 78 cb750 PD carbs into a good set from a 77 (spring clips to intake stays, instead of being coiled around the linkage shaft).

Here is my dilemma and I really need some insight.  On the "new" set, the idle adjustment screw doesn't even touch the arm that it is supposed to on the linkage shaft, even when fully turned in.  As a reference, I took a picture of both sets of carbs side by side to show the problem.

As you can see, I am putting pressure on the arm that the idle adjustment screw is supposed to make contact with, the screw is also fully turned in and still has a gap.




What is going on here, guys?  Please help me out, I'm at a loss.  Do I have to separate the carbs and pull the linkage shaft because it is installed incorrectly or something? 

Note- I did not install the linkage shaft nor separate any of the carb bodies

Thanks

[flybox1]

easy fix.. take off the top caps of the carbs.  reverse out the idle adjustment screw.
loosen the 4 screws (2 are in red below) that link the slide arms to the linkage shaft, then rotate the shaft (as you intended to with finger pressure on the idle adjustment stop ===>  see red arrow in picture) so the idle adjustment stop touches the idle adjustment screw.  the re-secure the 4 screws you loosened.
done.
you'll need to do a good bench and vacuum sync on these...

[dumpster84]

Thanks Flybox,  I thought that might have been the solution, but unfortunately it wasn't.  The #2 carb with the linkage that is not adjustable when synching, will not line up to screw the linkage back into the rod when I have the linkage shaft rotated to where I need it to go.  Does that make sense?  The threaded hole on the shaft will only line up when the shaft is rotated with the big gap between the idle adjustment screw and the arm.  The slides are bottomed out and can't go any lower, which prevents the slide arm linkage from lining up with the hole on the linkage shaft.  Ugh!

Here's a picture:


The #2 slide arm is in the lowest position I could get the slide to go and still get the screw into the linkage shaft.  Can the linkage shaft be installed 180 degrees off or something?  Also, look at this gap between the throttle stop and the cable linkage:



Something isn't right here or I am looking past something that is staring me in the face.

[flybox1]

can you make the adjustment here?  and rotate the throttle bell so it rests on the stop.

[flybox1]

A weird one for sure. 
It almost looks like the PO adjusted the throttle bell on the linkage to take up the throttle cable play at the bars...

[dumpster84]

No, unfortunately, not.  If you back off that nut, you can loosen the allen set screw and then the throttle cable linkage assembly part will rotate on the linkage shaft, but once you try to tighten it down again, then set screw will not line up with the threaded hole that is on the linkage shaft.  So basically, that assembly is stationary on the linkage shaft and cannot be adjusted with that set screw.

I don't know what the deal is.  The problem continues to be the slides are bottomed out and there is no more room to go down in order to rotate the linkage shaft enough that it makes contact with the idle adjustment screw as well as the throttle cable linkage coming in contact with the stops.

Anymore ideas?  I really appreciate the input so far! Thought we had it, but of course, never goes smoothly.

I have never removed the linkage shaft, but can they be installed wrong?  The slide arm linkage all looks new and shiny, so I have a feeling that the previous owner removed the linkage shaft at some point and re-installed it with new arms and what not.  I feel like if it was rotated more, it would line up right.  Can it be backwards or something?  UGHHH!

[flybox1]

you stated you replaced the internals.  Slides too?
If so, were the slides taller by chance, causing everything to stop short?

[dumpster84]

Worth a shot.  I'll go give it a try.  Man, if that's the case, I would be ecstatic.  I'll measure the slides first to see if they're any different.  The ones that came with it are darker than the ones I installed which are chrome.

[dumpster84]

Well Flybox,  looks like you might be on to something!!  Check it out!  Chrome one is the one i swapped in, dark was in originally.





It appears that the slide arms are the same length, BUT the little arm that screws into the slide that holds the needle down, is a different length!!! CRAZY!

You think I'll be good if I just swap the shorter little arm from the dark into the chrome slide and be good?  Or should I put my needles into the dark slides?

[flybox1]

IIWM, id use the original needles and just swap that linkage section. glad it was an easy fix...sorta 

[dumpster84]

Flybox, I owe you a beer, sir.  Thanks for helping me brainstorm that silly problem out.  I was losing my mind.

I ended up using the dark slides and short arms from the ebay set and just swapping my needles in.  The chrome slides were dragging a bit in the carbs, but the dark ones snapped up and down very sharply.

Also, once I installed the carbs, the return spring that just clips onto the front carb stay, SUCKS.  The throttle was soooo sloppy and returned from full throttle to closed in like 3 seconds instead of instantly like my 78 carbs were.  So, I put an additional spring on and now it's much quicker and snaps sharply.

Synched them up real quick and took it out for a rip and damn, it was spot on, felt soooo good, except my front brake needs to be bled a lot more......almost non existent.......ugh.



Anyways, thanks again Flybox!

[flybox1]

your posts and pictures made it easier to work through    i was perplexed for sure....
good sync there. see if you can get them sync'd with idle closer to 1k next time.
1500-1600rpm is a little high

[dumpster84]

your posts and pictures made it easier to work through    i was perplexed for sure....
good sync there. see if you can get them sync'd with idle closer to 1k next time.
1500-1600rpm is a little high

Thanks Flybox, I have definitely become very familiar with these carbs since I got this bike back in August, lots of tuning, synching, cleaning, cleaning, etc, but that issue was blowing my mind.  I seriously had no idea why it was like that, thanks for chiming in. 

As far as the idle speed, you're right, I finished synching them up right around 1100. in the picture, I had the idle turned up because they were all so far off because I barely did a bench synch and had to turn the idle up so it wouldn't die out on me.