Topic: carb problems

[Bandit18]

Well I've had the carbs off two times. The first time replaced all the o rings and cleaned all jets, the bike is a 1978 cb550k that was setting in my father inlaws shop for over 20 years but only has 5200 miles on it . I got in a hurry and wanted to hear it run  and the tank wasn't clean as it needed to be so the carbs were removed again and cleaned...this time I replaced the needles and new throttles cables. I started it today and the no.4 pipe is not heating up and when the throttle is worked the revs wont go down unless I twist the idle screw manually . I ran some seafoam and non ethonal gas and tapped on the side of the bowl with back of screw driver but it doesn't seem to be helping any help would be appreciated.
Thanks

[Bandit18]

Thanks I'll try to find the vacuum leak as you suggested.

[DaveBarbier]

I've read a few times people say they cleaned their carbs and then later on say something like, "My problem is still there so I'll remove the carbs and clean them again. I might have missed something or not spent as much time as I should have." Remove them, and clean them so you know they're clean so you won't second guess yourself.

The PD46C carbs have pressed in pilot jets. Did you remove them? Did you remove the emulsion tubes and main jets? Carb cleaner, small gauge wire and compressed air...works like a charm.

Apparently a hanging idle can also be caused by the carbs not being in sync. When you replace the needles, you'll have to re-sync the carbs. Start with a bench sync using a drill bit so you're close, then finish with a vacuum sync on a warmed up motor.

And yeah, the tank and fuel going to the carbs has to be free of debris, but that's probably obvious

[Bandit18]

Yes I removed the pressed in jet..I. used carb cleaner and compressed air. I believe I did a though cleaning and used a drill bit on slides to bench sync. I'm using a temp gas tank while I try to get it running correctly I don't know if that makes a difference or not. Thanks for your help.

[harisuluv]

1)So by what means did you verify the jets were clean?  I got a whole drawer full of jets I can spray with carb cleaner and compressed air and it won't do ANYTHING, it will be worthless as it's still 100% clogged. 

2)  Define "thorough cleaning." 

3)  Why would a gas tank matter?  A gas tank is just a vessel--a receptacle to hold fuel.  If you turn the petcock on and clean fuel comes out, that's all we need.

4)  "this time I replaced the needles" why and with what?  What exactly was the replacement (manufacturer, part number, aftermarket, oem, anything)

5)  "throttle is worked the revs wont go down unless I twist the idle screw manually" Sign of but not limited to a lean condition

6)  "and tapped on the side of the bowl with back of screw driver but it doesn't seem to be helping" - Usually this is done to help seat a float valve.  Are you having issues with fuel coming out the bottom?  (overflow drain)

[Bandit18]

As I said before the bike had been stored for more than 20 years with gas in tank and carbs. When I received it I removed tank and carbs originally I cleaned the tank with white vinegar but a part of the top wall was week so I found one on ebay mostly rust free, I've had it painted and its ready when I get carbs sorted out. The bank of carbs were soaked in pinesol for 24 hours then all jets and floats and needles removed. I scrubed whith small wire brushes and blew compressed air thru all openings till I was confident that they were clean. I soaked jets in carb cleaner over night and then used wires and compressed air to clean them, the slow jet was blocked and had to heat and spray carb cleaner and repeat till I could hold up to light and see pin hole. I replaced all o rings at first clean, on second cleaning I replaced needles because I noticed at least 2 0f them would not spring back. There is some gas coming out of overflow tubes so I did tap bowls while running. I will try to find a vacuum leak as suggested but was looking for tips to make sure I tried everything before I had to remove them again. Thanks again for your time.

[Scott S]

 I think he's talking about the fuel valves.....float needles.

[Bandit18]

Yes I do mean the float needles... Sorry not specific.

[harisuluv]

For #4 pipe you begin troubleshotting with:

1)  Fuel
2)  Spark
3)  Compression

Remember, Fuel doesn't mean check for gas coming out the tank, gas in carb bowl.  It means we need to figure out if fuel is making it TO THE CYLINDER.  Like, does #4 come to life suddenly with starter fluid?  If so you're not getting fuel from the tank to the cylinder, which is usually carb related.

If you want to make progress, this is how you will approach it with these three points of verification.  Otherwise, you are most likely just grasping at random straws.

[Bandit18]

I ran it twice today for about 10 to 15 minutes and it seemed that no 4 pipe did finally heat up. I sprayed wd40 on carb boots and at exhaust while idling and it didn't seem to make any difference in the high revs. It seems like each time I run it for a while it runs a little better. I was going to run it once more before it got dark but it would not turn over. Guess I'll do some more research on the forum and try again. Thanks for all your help.