• 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.

Richness on suddenly open throttle

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

Anonymous

Guest
Is it normal for an engine running CV carbs to run rich and churn black smoke when suddenly opening the throttle? I know that suddenly changing throttle can create wacky vacuum problems. I have a suspi cion that I might always have richness on full throttle, sudden or not. But it's a little tough for me to see my exhaust as I have the throttle wide open... Much acceleration. :D :D :D

So is some richness to be expected or should I rejet?

Michael
 
Suddenly opening the throttle when? After idling? While cruising 65 mph and suddenly opening the throttle?
 
Re: Richness on suddenly open throttle

Its probably nothing more than burning out accumulated carbon build up. If the bike is running strong with good acceleration, I dont see how it could do that if the mixtures were so rich as to produce black smoke. If the mixtures were that far off, I doubt the bike would top out at anything over 40 mph. :-)
I would run it a while and give it a chance to clean itself out. Check the plugs off and on, that will tell you how the mix is burning.

I would not just yet consider any jetting changes.

Earl

mopolopo said:
Is it normal for an engine running CV carbs to run rich and churn black smoke when suddenly opening the throttle? I know that suddenly changing throttle can create wacky vacuum problems. I have a suspi cion that I might always have richness on full throttle, sudden or not. But it's a little tough for me to see my exhaust as I have the throttle wide open... Much acceleration. :D :D :D

So is some richness to be expected or should I rejet?

Michael
Click to expand...
 
KEITH KRAUSE said:
Suddenly opening the throttle when? After idling? While cruising 65 mph and suddenly opening the throttle?
Click to expand...

Either. I can see that from idling on the sidestand to full open throttle causes smoke. I am also told that when a friend was driving next to me and I had it at 60 in second and gunned it, it also made a lot of smoke.

Michael
 
Re: Richness on suddenly open throttle

earlfor said:
If the mixtures were that far off, I doubt the bike would top out at anything over 40 mph. :-)
Click to expand...

Welp, I don't really know what my top speed is currently. Since I borrowed DEW's windshield I've been getting a nasty headshake at 103 or so... probably have plenty left. :D :D

Michael
 
Re: Richness on suddenly open throttle

If it was going rich at full throttle, it would bog and acceleration would fall off.
If its still pulling hard, I dont see how the mixtures are going too rich.

Earl

mopolopo said:
Welp, I don't really know what my top speed is currently. Since I borrowed DEW's windshield I've been getting a nasty headshake at 103 or so... probably have plenty left. :D :D

Michael
Click to expand...
 
Well, sounds rich to me. A little black exhaust can be acceptable on sudden opening, but not a lot of it. Which bike is this? Is this the bike you said is running good? The one with the carbs synched and the mixture screws set correctly? What else have you done to try to correct the problem? Did it at one point not smoke? What's happened since that point?
When you suddenly open the throttle at 60 mph, as you hold it open and you're accelerating, does it pull a little harder if you back off the throttle just a bit?
 
something with the needles maybe? quick accel (unless it's wide open then its running on the main jet) is gonna pull fuel through there quickly...

i was told over time they can shake and waller out the area they sit in.

~Adam
 
Re: Richness on suddenly open throttle

mopolopo said:
Is it normal for an engine running CV carbs to run rich and churn black smoke when suddenly opening the throttle? I know that suddenly changing throttle can create wacky vacuum problems. I have a suspi cion that I might always have richness on full throttle, sudden or not. But it's a little tough for me to see my exhaust as I have the throttle wide open... Much acceleration. :D :D :D

So is some richness to be expected or should I rejet?

Michael
Click to expand...

Great way to beat the word-editor! :lol:

Dm of mD
 
When you first wack open the throttle, if anything, it should go a bit lean I thought, but the CV carbs are supposed to eliminate the problem. If you're not having acceleration issues, I would just run it up to redline a few times and check it again, it could just be clearing it's throat. Also check your plugs and see what they have to say, preferably right after it has the issue.
Good luck
 
My theory on the issue is the fact that the slides are vacuum operated, not mechanical. When the throttle is wacked open, the butterflies on the engine side come open, fuel is sucked up through the jets, and a split second later the slides open. I would venture that during this split second is when the bike goes rich.

Just a theory...

:)
 
But if the slide is down, then the needle is down, and no extra fuel would be flowing, or is my logic flawed?
 
lhanscom said:
But if the slide is down, then the needle is down, and no extra fuel would be flowing, or is my logic flawed?
Click to expand...

Might-be-wrong zone ahead:

As I understand it, the velocity of the air in the carbs determines how much fuel comes out the venturi, due to the Bernoulli effect. The cross sectional area of the flow chamber (as determined by the height of the slide) is what determines the volume of air in the mixture. So if the vacuum is high, the air velocity will be high, and there will be lots of gas, but if at the same time, slides haven't yet risen, there will only be a little air. Lots gas plus little air = rich.

Or I might be totally dead wrong. (Please tell)

Now leaving might-be-wrong zone

Michael
 
Just some comments interspersed. :-)




mopolopo said:
As I understand it, the velocity of the air in the carbs determines how much fuel comes out the venturi, due to the Bernoulli effect.
************Thats right. Without sufficient velocity, there will be no fuel flow.


The cross sectional area of the flow chamber (as determined by the height of the slide) is what determines the volume of air in the mixture.
*************** The throttle plate being opened or closed causes a change in velocity/vacuum which causes causes the slide to move either up or down. Engine rpm and displacment determine the volume of air that will be drawn through the carbs.

If your engine processes 100 cu ft of air per minute at 1200 rpm, it will do so regardless of whether carbs are mounted to the cylinders or not. You could turn the crankshaft at 1200 rpm with an electric motor and the engine will pump the same 100 cu ft min of air.

Earl




So if the vacuum is high, the air velocity will be high, and there will be lots of gas, but if at the same time, slides haven't yet risen, there will only be a little air. Lots gas plus little air = rich.

Or I might be totally dead wrong. (Please tell)

Now leaving might-be-wrong zone

Michael
Click to expand...
 
OK. Now that we've got that scientific stuff out of the way, let's figure out why your needle and/or main circuit is rich. :)
How about my questions from my earlier post? Black exhaust can be just one carb too. It does'nt have to mean all the carbs are rich.
 
I haven't been out to see how the plugs look after a goof full throttle bit. I figure what I'll do is open up the throttle up a hill near my house. Should let me have open throttle for at least 5 seconds, then kill it and coast back down and have a look at the plugs.

But not yet.

Michael
 
Dude....your hand is probably gonna get slapped for that sig.

:?
Dm of mD
 
i'm ready to kick his shins. :P

you need to do the basic check first, run the bike hot, blip the throttle to where you normally see black smoke, shut it down immediately. procede to remove each spark plug and examine them to see how the engine is running. Keith made a good point that it could be one carb acting up...not all of them.

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