HIGH rpm / choke cable install

[LASERTURTLE]

Hello all,  I am new to the forum and I have to say already so thankful I found this place . With that being said I just when down to San Diego and pick up my new baby a 1977 CB750F super sport  after a new battery and a little adjustment of the idle screw starts up every time on the first try , now my problem is , after it gets warm it starts idling SUPER HIGH about 2500-3000 rpm’s now normally I just readjust the idle screw a little lower , yesterday I was looking over the bike and I came to realize the damn this has (in my excitement to get the bike I overlooked it) NO Choke where a choke should be. After all that being said I have never had to install anything like, this my last bike was a 2003 SV 650  (but this is my dream bike ) and I was wondering if anyone had a diagram or steps to be taken list in order to make my life a hellav a lot easier in installing the new choke / choke cable  …….. any advice would be appreciated thx

[LukeM]

Welcome to the forum.  We're glad you're here.

Here's some things to get started.

Download the Factory Service Manual from the home page of our forum.  It's free.  Read it.
If you're looking for older posts about choke cables, use the Search box on the same home page.  Chances are, it's been discussed on here more than once.

As far as the high idle, it's possible that there's some sort of air leak or perhaps a vacuum leak in the carb boots that gets worse when the engine heats up.  You can find it by using some carb cleaner and spraying around the carbs and boots. If the idle changes, you've found the air leak.

Good luck, and keep us in the loop about your bike.
Luke M

[LASERTURTLE]

Thanks for the heads up i will let you know what comes of it

[Hoosier Daddy]

Part of the choke assembly is a fast idle cam that raises the idle speed what the choke is applied. Not knowing exactly how the linkage is oriented on your SOHC carb rack, I wonder if it is holding the idle speed up. I could see it possibly rotating innto that position if your throttle is open and nothing to keep the cam released.

[LASERTURTLE]

I was thinking something along the same lines (that essentuly the choke was in the open position without ever closing due lack choke cable) ,  but i wont know untill i get the new choke installed this weekend i just placed the order yesterday on a rush delivery , so fingers crossed and all that  

[LASERTURTLE]

Here is a few picks of my baby

[Truck]

Nice bike.  Not sure if it's different on the SOHC from the DOHC, but the choke on my 900 is opened by the cable (I know this because my choke cable is currently a zip tie I pop on and off, hurray MMU).  You might want to check for sticking.

[Hoosier Daddy]

Truck wrote

Nice bike.  Not sure if it's different on the SOHC from the DOHC, but the choke on my 900 is opened by the cable (I know this because my choke cable is currently a zip tie I pop on and off, hurray MMU).  You might want to check for sticking.

HUH?
You mean on your 900 the choke defaults to "on" and the butterflies spring closed, but it's pushing in the choke knob in that opens them and the cable is the only thing holding them open?
 OR you pull the choke knob and it OPENS the butterflies?
If either one is the case, something is wrong...

[Truck]

When I pull on the cable (when I install one) It pulls up on the mechanism and activates the choke. Worked the same way on a buddies 79 750.

[Hoosier Daddy]

Ok, that makes sence...your choke plates are closed by the cable. It threw me when you said

 but the choke on my 900 is opened by the cable

[Black 750K8]

Laser wrote
 Hello all,  I am new to the forum and I have to say already so thankful I found this place . With that being said I just when down to San Diego and pick up my new baby a 1977 CB750F super sport  after a new battery and a little adjustment of the idle screw starts up every time on the first try , now my problem is , after it gets warm it starts idling SUPER HIGH about 2500-3000 rpm’s now normally I just readjust the idle screw a little lower , yesterday I was looking over the bike and I came to realize the damn this has (in my excitement to get the bike I overlooked it) NO Choke where a choke should be. After all that being said I have never had to install anything like, this my last bike was a 2003 SV 650  (but this is my dream bike ) and I was wondering if anyone had a diagram or steps to be taken list in order to make my life a hellav a lot easier in installing the new choke / choke cable  …….. any advice would be appreciated thx

 First off I am suprised the bike starts when cold winter time cold. The fast idle cam is the best feature on these pd carbs along with the pump. The Honda service manual describes in great detail how to set it up. But if there is something you don't quite understand just ask away we have all been there and that is why we are here now to help if we can. Keep in mind the manual covers 69-78 750s you need to go to the the back of the book to find the 77-78 part for your carbs. When set up correctly When you pull the choke all the way up this is what should happen first the pump rod activates the pump (so the gap if any is important) just a little giving each carb a little raw fuel this is a good thing no twisting the throttle next it sets the linkages as if you are holding the gas open a little see it is doing everything for you. Instead of a 1100-1200 idle when the choke is all the way up it will now idle at 2700 +/- 750 rpm so within a few seconds you need to start pushing the choke a little at a time this is when you should get out of dodge be dressed ready to go this is not the time to be farting around get the bike going and push the choke all the way down as soon as you can so you don't start fouling the plugs. You will not believe how much better it starts in the winter and firsts starts in the summer. you will never need to mess with that big idle screw again set it when the bike is warm and leave it alone. Now I have just hit on the high spots here so when the time comes to do it fire away