Topic: Was balance tube question, now: HELP ME FIX THESE PD CARBS!!

[Scott S]

 Bike is a '78 550K with PD46C carbs.

 If I have a leak at one of the balance tubes between the float bowls, does that mean my fuel level is too high? It doesn't seem like fuel should be that high in the carb bodies.
 This is a new leak that I haven't experienced before. Recently set floats heights per instructions on this site (for about the third or fourth time).

EDIT I now know those aren't the balance tubes but are the fuel line feed tubes. I will be pulling the carbs again to replace o
O-rings. GRRR!!!

 

[flybox1]

if you want to verify gas height without removing your carbs, throw on some clear tubing and check. 
you'll see right away which one it is.
might just be sediment from your gas or tank blocking a float valve.

[Dave Voss]

If you are referring to the horizontal tubes just above the float bowls between adjacent carburetor bodies, those are the fuel supply lines, which are normally filled with fuel.  A leak at the ends of those tubes is not uncommon, as there are o-rings inside the carburetor bodies, which typically need replacement at some point in the life of these old motorcycles.

[Scott S]

If you are referring to the horizontal tubes just above the float bowls between adjacent carburetor bodies, those are the fuel supply lines, which are normally filled with fuel.  A leak at the ends of those tubes is not uncommon, as there are o-rings inside the carburetor bodies, which typically need replacement at some point in the life of these old motorcycles.

 After posting, and going for a drive to clear my head, I realized they were feed tubes.
 I'll start another post probably, but these things are kicking my butt. It acts like it has an air leak, but I CAN NOT find it. Pulling better at high rpm's now, but can't get the idle right.

[flybox1]

vacuum sync done?

[Scott S]

 Yes.
 Carbs cleaned by me three times. Just had a local pro go through the idle and pilot circuits and we confirmed that all of that is open and operating as it should.
 
 Set float heights AGAIN, this time at 12.5 mm measured at the middle of the float to the carb body. This seemed to help the top-end, as did lowering the needle back to stock and a smaller main jet.

 This thing sounds horrible if it idles anything under ~1400. I would just live with that, but now the idle is wanting to move around again. It acts like a vacuum leak, but I can't find one anywhere. O-rings on manifolds were new, but if I pull the carbs I'll replace them again if I can find a set.
 Tried two different mechanical advancers. Just did the 3K mile tune-up less than 20 miles ago.

 One thing: I didn't vacuum synch the carbs after re-installing them this time, but I didn't do anything to that part if the carbs. All we did was clean the idle and pilot jet circuits.

 Either way, they're coming off again to get those O-rings fixed and will have to be re-synched then.

[LesterPiglet]

If the carbs were dirty before the last cleaning then you will need to re-sync them as fuel flow will have been affected.

[flybox1]

check valve lash, and reset timing/advance and cam chain.
then, vacuum sync.

[Dave Voss]

check valve lash, and reset timing/advance and cam chain.
then, vacuum sync.

Follow this very good advice, in the order listed.  In my experience, smooth idle is best achieved when all of the valves are adjusted exactly the same, and the carbs are vacuum synched following all other adjustments.

[Scott S]

If the carbs were dirty before the last cleaning then you will need to re-sync them as fuel flow will have been affected.

 I had cleaned them but was unable to remove the pilot jets (pressed in style). Rick at oldskoolcarbs found two vents on the carb bodies plugged. He said this may or may not have been affecting fuel flow/level in those carbs.
 He pulled the idle mixture screws and cleaned those passages. The pilot jets will NOT come out. Rick has a fixture to hold the slides/butterflies open and he attaches a hose completely around the pilot jet. When spraying cleaner through the pilot jets, it comes out of the orifices in the carb bodies. He also uses a small wire to clean the hole.
 Optimal? No....I'd rather pull and clean/replace the pilots but, I'm telling you, they are NOT coming out. Rick has done hundreds of carbs of all makes and models and knows when to yell "Uncle". He felt we would damage the carbs if we tried any harder.

[Scott S]

check valve lash, and reset timing/advance and cam chain.
then, vacuum sync.

Follow this very good advice, in the order listed.  In my experience, smooth idle is best achieved when all of the valves are adjusted exactly the same, and the carbs are vacuum synched following all other adjustments.

 Just before the last tuning session, I did ALL of those things. I did nothing more than tune in the garage and ride maybe....MAYBE 10 miles around the neighborhood testing.
 The valves and cam chain adjustment have less than 10 miles on them.

 I will double check the timing when the carbs go back on. I will vacuum synch again when the carbs go back on.

 I also pulled the manifolds tonight and changed the O-rings. All manifolds were tight and the O-rings showed no evidence of leaking, but I changed them anyway.
 All manifold to carb rubbers are in good shape and supple enough to squeeze with my fingers. The carbs seat tightly and I always go back after getting heat in the engine and check the band clamps again.