Topic: Choke question. How's it work and how'd I break it? ( :

[Fish]

Hello gang,
My little project is coming along pretty well but I have a question about my choke.  When I first got my bike, the choke functioned like it should ie, when I opened it, it helped start the bike but when the bike was warm I would have to ease it close to prevent the engine from racing.
Since then, I performed a tuneup which included adjusting my valve clearance, my point gap (at about .35mm), and my timing (lined up right on the 'f' mark).  The bike 'seems' to be running good (maybe doesn't start as easy) but now the choke doesn't help at all, and when I open it, it bogs the engine down and will stall it. 
I know that I probably have something out of whack but I'm not sure what I need to adjust or which direction I need to adjust it. 
Thanks for any ideas.

- Chad

[TwoTired]

Near the air inlet of each carb is a butterfly valve.  These are the chokes.  They are linked together and operated by a lever on the far left carb.  When the lever is pulled up, the choke butterfiles should be all closed.  This blocks off much of the inlet air and forces more fuel to be drawn from the fuel metering jets, richening the mixture for cold operation.  When the choke lever is down, the butterflies should be fully open, allowing maximum air to enter the carb throat and for them to operate in the normal run regime.

If you de-racked the carbs for cleaning, then attention must be paid to the interlink mechanism while reassembling the bank to insure all the choke butteflies operate in unison.

Cheers,

P.S. Didn't you have plugged slow jets when you got the bike?    You likely had to operate with choke to draw extra fuel from the mains, just to keep it running.  Hardly normal operation.

[Fish]

Thanks for the crash course.  You're right, I did have a plugged slow jet and I cleaned the jets without having to separate the carbs so the linkage should be ok still.
I just thought it was strange that my choke is completely unnecessary now and will actually stall the bike if I open it.  Don't most people use the choke when they start from cold?  I can't.

- Chad

[TwoTired]

On a hot summer day, I don't need to use choke on the Cb550's (early carbs).
Cool mornings, yes.  Certainly in the winter.
If I had to guess, I'd say above 70 F, no choke needed.  Below that, some, with increasing amounts as the ambient temps gets colder.

I'm confused by your terminology, though.
Here is what I believe is standard:
Lever up = Choke on = butterflies closed = choke closed.
Lever down = Choke off = butterflies open = choke open.

Cheers,

[Fish]

Uhh, ya  my terminology is completely screwed up - sorry.  I meant to say that when I have the lever up, choke on, the bike wont start or the engine stalls; when the lever is down, choke off, the bike will start and idle normally.
It is about 78 degrees here so I guess that it is completely unnecessary to use.  I just thought that if the choke was working properly, even on a warm day, it would speed up the engine with it on (not that I want the engine sped up. just for the sake of testing).  This behavior seems opposite what I expected, and have experienced in the past.  I thought that my ignition or fuel delivery might be off so that when the choke was activated it provided too much or too little fuel to run properly... 

- Chad

[seaweb11]

90 degrees here. choke on for about 4 seconds then off.

[Fish]

Thanks seaweb.
The plot thickens.  I don't expect to have to use mine much if it's nice and warm, but right now the bike won't start at all with the ckoke on.

And my condolences about the 90 degrees  . 
- Chad

[TwoTired]

  I just thought that if the choke was working properly, even on a warm day, it would speed up the engine with it on (not that I want the engine sped up. just for the sake of testing).  This behavior seems opposite what I expected, and have experienced in the past. 

Many choke systems have a coupled fast idle cam, to bump up idle when applied. Only the 77-78 CB550 K model carbs have this device.  The rest of the Cb500/550's rely on the twist grip for fast idle when needed.

Heat wave here in CA.  I'm sitting here, 80 degrees with the A/C on.  Outside; 97 (down from 105 yesterday), Garage; 95.

Cheers,

[mr_jason]

if i have the choke on when it's really hot out (over 85) it just dies for me too, but starts right up without the choke.  in the winter, i have to use the choke to start it up.  i think that it's normal, but two-tired would know much better than me.

[seaweb11]

" Only the 77-78 CB550 K model carbs have this device"

Does that explain why I have been confused over the years reading posts about guys who have the choke on for miles and miles in cooler temps, when my K8 only needs a choke on for a few hundred yards even in the winter?

I read here all the time how hard these 750s can be on cold starts and mine starts with a 1 second push of the button with the choke on full even below zero and as soon as I pass the 5th house I turn it off!

[Fish]

Mr. Jason,
Awesome.  Sounds like I'm not the only one.  Great looking bike by the way!

- Chad

[mrbreeze]

Ditto on the heatwave Lloyd.It's been in the above 105's out here in the valley the past few days.My bike always needs a choke to start (straight 4 into 1,K&N pods, Dyna ignition,138 mains,) but as soon as it kicks ,I turn it down halfway and kind of baby it with the throttle.It will do it's little cold -blooded  BS thing for a bit and then I turn it all the way down.I am usually running smooth on all 4 holes in less than a mile.These bikes are generally touchy when cold and alot of people have different starting techniques.You just have to get used to your particular set-up I guess.