Topic: 77 550k carbs - assembled wrong?

[Surly]

I've had a little trouble with the running of my bike. I think I may have assembled the carb linkage wrong. The bike ran all last summer but not as good as it should have. Here's the symptom. I can push the throttle (grip) forward and actually close the slides a little more than the "at rest position". If I screw the idle stop all the way out to where it is obviously not touching I can still close the slides some. The cables seem to be adjusted properly as well, so I don't think I'm stretching the open cable. The bike did not run before the rebuild so I have no point of reference. Is this a common newbie problem?
As you can imagine the bike is a bit hard to start in this condition.

[TwoTired]

Assuming you still have the PD carbs on the bike...
Check your choke cable/linkage and adjustment.
Not only does this actuate the choke butterflies, but it also is coupled to a fast idle cam that blocks the throttle return during actuation.  There is also a separate fast idle adjust screw that works in conjunction with the fast idle cam.

Verify that you can not only fully actuate the choke, but that you can fully disengage the choke as well.

Cheers,

[Surly]

I do believe the carbs are the correct stock items. I should have some time tonight to sheck things out. I will definitely look into the choke cabe and its adjustments. Something I should have mentioned before...the choke knob tends to fall down during warm up. I assumed this was due to a worn detent but perhaps there is another issue. Thanks and I'll check back after I fiddle with it.

[TwoTired]

...the choke knob tends to fall down during warm up. I assumed this was due to a worn detent but perhaps there is another issue.

The base of the choke knob mount is also a friction adjust.  But, if you've already tightened that down, replace the whole choke cable.

Cheers,

[Surly]

First, I tightened down the choke lever and it stays up. Thanks, I had no idea that there was a friction adjust. I then adjusted the choke lever per the factory manual and it was pretty close to begin with. Now as for my original "problem", when the choke is off you can turn the throttle forward and close the slides more than the idle position. When you let go it snaps back to the idle position. Is this just the way these work? They are the stock PD's BTW. I noticed after removing the tank, that there was gas (dried, varnish) on top of the float bowls. I think the crossover tubes may be leaking. How would this affect the running of my bike?

[TwoTired]

If you are certain the fast idle cam is not interfering with throttle return, here are some other possibilities.

- Throttle cable adjustment.  The two cables need a bit of slack on both at rest. You should be able to wiggle the twist grip about an 1/8 of a turn before taking up the slack in throttle roll on.
- Cable routing.  If different from the stock routing, can cause cable friction/bind.  Cables work the best and have the least friction when they have no bends.  And, the sharper the bend, the more friction is encountered.
- Cable lubrication is important.  Unlubed cables don't move as freely as well lubricated ones.
- Frayed core.  The multistrand center wire can fray when worn.  And, the protruding wires can impede smooth actuation.

- The carb slides can become gummy and not move in the carbs freely.  If there is some resistance to movement, they don't return to idle position without "Help".

- The symptoms you describe may also be attributable to the carbs being out of synch.  All the slides must have openings equal to the others.  At idle they are not fully closed.  And, if one is slightly more open that another, that cylinder will try to run faster than the others until extra force is applied to throttle return.

- Lastly, have each of the four Idle Mixture Screws been adjusted per manual?

Good Luck!

[Surly]

Sorry for the infrequecy of my replies, been real busy.  I played around with the carbs last night. There was no freeplay in the cables so I need to adjust that. The throtle disc that the cables attach to does not return all the way to the stop cast into the carbs unless it is forced by the close cable. When the bike was running this would obviously shut the carbs down to the point of almost killing the bike. (its not running now only because it's 20 degrees in my garage and the battery is in the house.) If I disconnect the cables entirely, the disc will still not return to the stop. I believe when I assembled the carbs on the bench I may have done something wrong. I will try to take a pic and illustrate my point better. I do have the factory manual but my copy has crap pictures and I couldn't find a procedure for adjusting the disc.