• 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.

high idle after carb synch?

  • Thread starter Thread starter robinjo
  • Start date Start date
R

robinjo

Guest
A friend and me as his lovely assistent 8) synchronised the carburtors of my Katana 1100 yesterday, turned out #2 was way out. So we adjusted it, put the tank back on and adjusted the idle back to about 1100-1200 rpm and get some coffee. About 2 hours later I start it to go home again and it idles at 3500! 8O quicky reached for the idle adjust knob but it didn't have any effect :?

So when I got home I turned the 3 adjusters out about half a turn and now it idles at about 1400 again but of course now it is out of synch again! :evil:

How can this happen :?: I'm stumped...
 
It appears that you have incorrectly placed the handcuffs and they are making it difficult for you to use your special took which is kept in your apron pocket :roll: once you remove said handcuffs and correctly place them your special tool will be able to do it's job properly :twisted:

So apart from syncing the carbs did you do anything else ?
 
Re: high idle after carb synch?

robinjo said:
A friend and me as his lovely assistent 8) synchronised the carburtors of my Katana 1100 yesterday, turned out #2 was way out. So we adjusted it, put the tank back on and adjusted the idle back to about 1100-1200 rpm and get some coffee. About 2 hours later I start it to go home again and it idles at 3500! 8O quicky reached for the idle adjust knob but it didn't have any effect :?

So when I got home I turned the 3 adjusters out about half a turn and now it idles at about 1400 again but of course now it is out of synch again! :evil:

How can this happen :?: I'm stumped...
Click to expand...


So you rode it home with the high idle? So it revs up fine with the throttle, but doesn't go down when you adjust the idle screw down?

Intake boot leaks?

Michael
 
Re: high idle after carb synch?

Robinjo, I will assume that you dont have any intake leaks, havent made any jetting changes, or airfilter changes since it was last running normally. I will further assume you are capable of looking at your throttle cable and identifying slack and a throttle linkage that is fully returning to the stop. LOL :-)

Now for synching........81 kat, thats going to be CV carbs.
There are 4 adjustments, not 3. You have the throttle plate position to adjust on 1,2 and 4. 3 has no throttle plate adjuster screw. The adjustment on #3 is changed by turning the idle adjustment knob either in or out. (which also will change the idle setting on 1,2 and 4) Do not change the idle adjustment knob setting during the synching process unless it is required to change the vacuum draw on cylinder 3. Set cylinder three vacuum to 10 in Hg @1200 rpm with the idle adjustment knob with the engine warmed up and idling without any choke.
Then set the throttle plate adjusters on 1,2 and 4 to draw 10 in Hg at the same 1200 rpm. If your vacuums are very far out of synch, you will get a variance in the baseline setting on #3 and will have to repeat the process, starting with resetting the base vacuum on #3. I adjust cylinder 3 with the idle adjustment knob to the baseline vacuum setting I want to synch to and once I have this, I adjust 1,2 and 4 independently to match that vacuum without again touching the idle adjustment knob. Once all vacuums match and I am through with 1,2 and 4, then I can change the idle adjustment setting, which will now change all four carbs while keeping them equal and increasing or decreasing idle rpm. I set all vacuums first to 10 in Hg @ 1200, then change rpm as needed.

Vacuum controls mixture and it is your mixture that is not quite right. Set the mixture first.

Earl


robinjo said:
A friend and me as his lovely assistent 8) synchronised the carburtors of my Katana 1100 yesterday, turned out #2 was way out. So we adjusted it, put the tank back on and adjusted the idle back to about 1100-1200 rpm and get some coffee. About 2 hours later I start it to go home again and it idles at 3500! 8O quicky reached for the idle adjust knob but it didn't have any effect :?

So when I got home I turned the 3 adjusters out about half a turn and now it idles at about 1400 again but of course now it is out of synch again! :evil:

How can this happen :?: I'm stumped...
Click to expand...
 
So then what needs to be done first? Sync, or set the mixture screws? :twisted:
 
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



slowfoxbird said:
So then what needs to be done first? Sync, or set the mixture screws? :twisted:[/quote
]
Click to expand...
 
Re: high idle after carb synch?

earlfor said:
Set cylinder three vacuum to 10 in Hg @1200 rpm with the idle adjustment knob with the engine warmed up and idling without any choke.
Click to expand...

How do you determine where 10 in Hg is? I have a mercury carb stick, and it has "hash marks" on it, but no scale.
 
Re: high idle after carb synch?

My mercury carb stix is calibrated in 2 inhg increments starting at 4 inHg and ending at 54 inHg.

Earl


renobruce said:
earlfor said:
Set cylinder three vacuum to 10 in Hg @1200 rpm with the idle adjustment knob with the engine warmed up and idling without any choke.
Click to expand...

How do you determine where 10 in Hg is? I have a mercury carb stick, and it has "hash marks" on it, but no sc
ale.
Click to expand...
 
robinjo, I think I know what happened.
I think you hooked up your vacuum tool and created an intake leak.
Then you started the bike and saw that cylinder reading way off (below) the others. You then made your adjustment and turned up the vacuum. The bike ran fine at that point because the two things cancelled each other...an intake leak (loss of vacuum) and an over adjusted throttle valve trying to compensate (increase in vacuum). Then you adjusted the idle and buttoned it up.
The next time the bike is started, with no vacuum leaking now, the rpm's go way up and of course turning the idle screw adjuster had no effect.
It's easy to create a vacuum leak when installing the carb tool adapters.
Try the synch again and be sure the adapters are on right.
 
KEITH KRAUSE said:
robinjo, I think I know what happened.
I think you hooked up your vacuum tool and created an intake leak.
Then you started the bike and saw that cylinder reading way off (below) the others. You then made your adjustment and turned up the vacuum. The bike ran fine at that point because the two things cancelled each other...an intake leak (loss of vacuum) and an over adjusted throttle valve trying to compensate (increase in vacuum). Then you adjusted the idle and buttoned it up.
The next time the bike is started, with no vacuum leaking now, the rpm's go way up and of course turning the idle screw adjuster had no effect.
It's easy to create a vacuum leak when installing the carb tool adapters.
Try the synch again and be sure the adapters are on right.
Click to expand...

Keith I think you got it!

But I will have to check the next time I have a synch tool available to adjust again.

Earl thank you very much for that info on synchronising and adjusting the idle mixture, it is being copied and pasted in to a document I will print out for future use.
 
Youre very welcome. :-) There are few things more pleasant than being able to not touch the bike for a week, and then just turn the ignition on, use no choke, touch the starter button, have the engine turn over one revolution and sit there idling smoothly. Thats my 1150. :-)

Earl

robinjo said:
Earl thank you very much for that info on synchronising and adjusting the idle mixture, it is being copied and pasted in to a document I will print out for future use.
Click to expand...
 
I also saved a copy of the tuning instructions. Thanks, earl! I do have a couple questions though:

When you say 10 in Hg, what is that 10 in HG relative to? In chemistry class we learned about how inches of mercury is a measurement of pressure and all. Measurement of pressure goes from 0 in Hg (absolute vacuum) to 29.92 in Hg, which is atmospheric pressure. From there you can go way up in pressure.

But when you're measuring vacuum, not pressure, does 10 in Hg mean 10 in Hg less than atmospheric (29.92) or 10 in Hg from zero? I'm inclined to think that it means 10 in Hg less than atmospheric, but I'm looking for confirmation.

I ask because I may have to do a carb sync with a tool not quite meant for the job, but which still reads pressure.

Thanks!

Michael
 
Michael, if my memory is correct, standard atomspheric pressure is 29.92 @ 68F at sea level. Temperature and density altitude modify pressure and that is why it is determined at a specific altitude and temperature..
From 0 in Hg to 29.92, and upwards, it is all on the same scale. Any reading is a pressure level. 10 in hg is a pressure level. Its just a pressure lower than standard. Since a mercury carb stix is open to atomsphere, then zero on the carb stix scale represents atomsphere. So we can say 10 inches of pressure less than that (what we would have when referring to setting the carbs to 10 inches of vacuum) would be an atomspheric pressure of 19.92

I hope this is at least as clear as mud. :-) :-)

Earl


mopolopo said:
I also saved a copy of the tuning instructions. Thanks, earl! I do have a couple questions though:

When you say 10 in Hg, what is that 10 in HG relative to? In chemistry class we learned about how inches of mercury is a measurement of pressure and all. Measurement of pressure goes from 0 in Hg (absolute vacuum) to 29.92 in Hg, which is atmospheric pressure. From there you can go way up in pressure.

But when you're measuring vacuum, not pressure, does 10 in Hg mean 10 in Hg less than atmospheric (29.92) or 10 in Hg from zero? I'm inclined to think that it means 10 in Hg less than atmospheric, but I'm looking for confirmation.

I ask because I may have to do a carb sync with a tool not quite meant for the job, but which still reads pressure.

Thanks!

Michael
Click to expand...
 
KEITH KRAUSE said:
STOP IT!!!!! :x You're giving me a headache!
HC, hg, Hcgh...phooey!
Click to expand...

We could use PSI or mm Hg or Pascals or Torr if you like.

:wink: :lol:

Michael
 
You must log in or register to reply here.
Back
Top