Topic: Why would the choke act in the opposite manner as intended?

[Beastman]

Here are the facts:

1978 cb550k: 4 into 1 yoshi rep pipe. Bigger jets (went from 90 to 95), needle clip moved to center notch.  Cleaned carbs, cleaned gas tank rust.

My bike's choke now works opposite.  If the bike is idling at 1200 or so, and I turn on the choke, it does.  Any idea why this would happen?

I know this is prob not enough info.  Please ask for specifics if this is too vague. 

[mlinder]

Why would you put on the choke when it's already warmed up?

If it's warmed up, you are bogging it down with too much fuel when you use the choke.

[Hannibal Smith]

Sorry, no input..................but where did you get the replica Yoshimura pipe?

[Beastman]

Why would you put on the choke when it's already warmed up?

If it's warmed up, you are bogging it down with too much fuel when you use the choke.

I can't start the bike with the choke.  I have to raise the idle for the bike to start. Then turn the idle back down once it's run for a bit.  The choke used to get my bike up around 3000 rpm, now it just kills it.

[nayto550]

Was air intake modified at all (high-flow filter, pods, etc.) when you did the pipes and jetting?

[phil71]

is this a CV carb?

[Beastman]

No mods to the airbox.  Besides disconnecting and reconnecting at the rubber boots.

The carbs are PD keihin carbs.

[mlinder]

It sounds like you've got it rich enough to not need choke to start, especially now that it is warming up outside in most places.

Choke is just too much fuel now.

[vames]

Sounds like you're trying to use the choke as a sort of fast-idle mechanism, which it isn't (unless later models have a fast idle cam that earlier ones didn't). If the bike is already started, you don't need the choke. Many of our bikes take a few minutes or a few blocks riding to warm-up before they'll idle on their own -- for that, we typically keep a hand on the throttle and keep it running. Soon enough it's warm and idles on its own.

[Beastman]

I was under the impression that the main jet/needle did not effect fuel delivery at idle.  Only when the throttle is opened up.

[333]

I would start over.  What told you to re-jet it and change the needle?  Sometimes a new pipe requires no re-jetting, and if it does, it could go either richer or leaner.

[Beastman]

I was told by some reliable guys here that the PD carbs run lean, and even leaner/hotter with an open exhaust.

Maybe I will start over.

[MasterChief750]

my pds run really rich from the factory. if your choke is killing it on startup and you dont need it to start it your carbs are rich. have you done a plug chop at all?