• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

Tuning my CV carbs

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

Guest
Alright, today I got in my brand new carb stix, and some new mixture screws. How much vaccum should my carb stix read, because I am pretty sure its graduated in cm instead of in. Also, where do I start out with the mixture screws on the CV carbs of my '83 GS750E, with pods?
Any help with tuning this bike would be greatly appriciated. :twisted:
 
I've taken to making an archive of Earl's procedural wisdom. Here's a reprint for you. The thread was "High idle after carb adjustment"

Michael

On CV carbs, pilot fuel and air are combined into one mixture screw. I set the #3 carb to baseline vacuum using throttle plate adjustment, then set the mixture screw on it for highest idle rpm. Then set the idle adjustment knob to return to 1200 rpm idle. Re adjust throttle plate on #3 to 10 inHg vacuum. Then set the fuel/air pilots (mixture screws) on 1,2 and 4 to the same number of turns as #3. When you have 1200 rpm and #3 is drawing 10 inHg vacuum, you have your baseline and then can set 1,2 and 4 to draw the same vacuum as #3. Once #3 is set to base, you must not touch the idle adjustment knob again. Only when all 4 cylinders draw the same vacuum and rpm remains at 1200 may you change the overall idle rpm if you wish.

Setting the mixture screws doesnt do you any good if you dont have the correct intake velocity (vacuum) for the screw setting. After you set up #3, that is why you cannot make any more changes with the idle adjustment knob. Its impossible to synch vacuums if youre constantly sending the reading all over the scale with the idle adjustment knob.

Earl
Click to expand...
 
OK, I understand that, now what do I do about the measurment of my carb stix? I got the shop quality carb stix out of the Dennis Kirk book, but I think it is graduated in cmHg, not inHg. What the heck is Hg anyway? :twisted:
 
in Hg stands for Inches of Mercury, chemical symbol Hg. You can measure the difference in pressure between two environments by how far the lesser one will suck a tube of liquid. Think of it this way: if there were marks on your straw as you suck water from a fountain cup at McDonalds, it would measure the difference in pressure from the suction of your mouth to the environment around you.

People use liquid mercury because it is 11 times as dense as water. You could have a much safer tool (Hg is bad stuff) by using water but the water would have to get sucked up 11 times as high, so 10 in Hg would be 110 in H2O, or almost ten feet in the air. And since your carbs sit at about two and a half feet above the ground, good luck getting a ten foot vertical suction of water. :)

10 in Hg = 25.4 cm Hg

Michael
 
Ok, thank you very much Michael, I am going to try to get something done on the bike and let you know how it goes.
:twisted:
Matt
 
You must log in or register to reply here.
Back
Top