Topic: '72 CB500 Choke Question

[AzCb500]

Hey Guys/and Girls! Just picked up my first CB500 this afternoon and just wanted to get acquainted with everyone here on the forum. I traditionally have ridden KZ's but have really loved the CB's and figured I'd give it a shot. I really hope to learn a lot about these CB's and want to thank everyone in advance for any help given.

To start off when I got the bike it would only start/run with the choke in the OPEN position.
I can slowly turn it to the CLOSED postion, but once fully closed the bike bog's down and shuts off.
The previous owner is telling me he has just cleaned and tuned the carbs and that he thinks the choke could be functioning backwards? (Im not sure if he means the butterfly valves work the opposite direction or something?)
Is this even possible and if so whats the easiest way to determine whether it is backwards?

I have a feeling the jets or something in the carbs may be blocked or something but I wanted to double check with you guys first before tearing them off and going through them. Thanks

AzCb500

[DavePhipps]

In normal operating conditions the bike should only be run in the open condition. When the choke is closed the butterfly valves block the air supply leading to a rich condition to aid in starting. During warm weather I don't even need the choke but I have been told by others that they always need the choke for starting the bike. 

[Jimsun]

Hey Guys/and Girls! Just picked up my first CB500 this afternoon and just wanted to get acquainted with everyone here on the forum. I traditionally have ridden KZ's but have really loved the CB's and figured I'd give it a shot. I really hope to learn a lot about these CB's and want to thank everyone in advance for any help given.

To start off when I got the bike it would only start/run with the choke in the OPEN position.
I can slowly turn it to the CLOSED postion, but once fully closed the bike bog's down and shuts off.
The previous owner is telling me he has just cleaned and tuned the carbs and that he thinks the choke could be functioning backwards? (Im not sure if he means the butterfly valves work the opposite direction or something?)
Is this even possible and if so whats the easiest way to determine whether it is backwards?

I have a feeling the jets or something in the carbs may be blocked or something but I wanted to double check with you guys first before tearing them off and going through them. Thanks

AzCb500

I have the first gen cb550 ('74). The bikes starts only with the choke closed. After it has started, i would apply some throttle and close the choke. When you get use to it, it'd take less than 5 seconds. Close choke, kick start/electric starter, applying throttle, open choke and maintain 2k rpm. After about a minute or when it's warm, i can let go of the throttle and it'll be fine.

[Stev-o]

"Choke talk" can be confusing. When starting a cold engine, put the choke in the on position, which blocks off air entering the carb, as Dave stated above. 
If the bike will only run in this scenario, sounds like you have a carb issue, most likely clogged pilot jets.

DONT ever believe what a PO tells you! It this case, he may have cleaned the carbs, but possibly did not do it properly. 

[riverfever]

My 71 starts cold with the choke in the open position just like you describe. I have gone through the carbs and rebuilt them along with adding Dyna coils. Right now I know I have issues with the points and condensers. There's too much resistance and I think this is causing weak spark and a rich condition (plugs 1 and 4 are soaked). I will install Dyna ignition soon and hopefully that will help. The guy I bought mine from also said the carbs didn't need going through. I was amazed the bike even ran at all.

Dave and Steve are correct in how it should operate though.

[DavePhipps]

OK you are referring to having the butterflies closed.
First thing to do is find out which carbs you have what jets are supposed to be there, needle and screw setting. Compare that to what you have.
Check for dirty air filter, check carb rubbers for leaks, check fuel lines and filters, make sure petcock is flowing fuel properly (I chased that for a month before finding out my petcock was clogged).
After all that do a carb sync. That's my methodology at least.

[brooze72]

For a cold start mine works like this..choke on (lever in the up position) start engine, after 30 sec I drop the choke to 1/2 way, couple more minutes at 1500 rpm the choke off & good to go. If it's a very cold day it might still be boggy for a block.  On a warm day, no choke needed for a restart within a few hours, maybe a touch of choke if it's been all day since the last start.

[DavePhipps]

Man.. I haven't ridden my CB for over a year. I can't remember which direction is butterflies closed LOL
I just went outside to check, down is butterflies open so no choke.
So you have a bike that is running well and sounds like it's warmed up and you suddenly cut off it's air supply. They run like crap when you do that. Sometimes in cold weathewr I forget to turn the choke off and about a quarter mile down the road my bike starts sounding like yours does in the video. Choke off and I'm back on the road.

If you are used to CV carbs this will seem backwards as the butterflies on those have a different function.

[Stev-o]

Why are you turning the choke on when the bike is running??

[DavePhipps]

Me or him?
I had mine on because is was 20 degrees Fahrenheit outside, had to get to work fast and forgot to turn the choke off.

[Stev-o]

Me or him?

Him

[AzCb500]

Im just used to the choke on my KZ, it seems like this is backwards compared to that. Just wanted to confirm this is the right position for the choke to be in. Sorry for any confusion and as you can tell I'm definitely new to the CB's haha