Topic: -Updated and found the problem- carb syncs telling me about other problems?

[TwoTired]

The CB550's pilot circuit is a separate carb circuit with no control input from the twist grip.
The early carb's pilot circuit has an air control screw to regulate the air going the pilot jet's emulsion tube.  The resulting premix is delivered in its entirety to the carb bore at a rate variable with the vacuum presented at the pilot circuit exit port.  The vacuum intensity is greatest when the slide is at it's lowest point, and diminishes as the slide is raised.

Further, there are two types of pilot screw on the early Cb550 carbs, the F carbs have a solid tipped screw allowing for all the air to be blocked from pilot circuit premix.  The rest have a a hollow tipped and cross drilled tip screw, which limit the minimum amount of air premix to that of the cross drilled hole size.  This screw tip type effectively creates a lower limit to just how rich the idle mix can be adjusted via screw setting alone.   The pilot circuit air supply has a inlet jet (ahead of the pilot screw adjustment), which sets the limit on how much the circuit can be leaned with any given pilot jet size no matter how far out the screws is turned.  The practical limit of pilot screw adjustment outwards is about 5 full turns with rapidly diminishing effect beyond 3-4 turns outward.

The idle mix for these carbs is purposely rich in order to compensate for mixture starvation when the carb slide is raised, causing rapid vacuum loss in the carb throat and the resultant loss of fuel draw.  Therefore, in practice, the pilot circuit is adjusted to achieve predictable power advancement when the throttle is twisted up to one half of the remaining travel at any engine RPM and in any selected gear.

The book's printed settings only apply to the stock air induction and exhaust back pressure.  Any change to these components have more than a cosmetic effect to the machine's operation.  Pilot circuit, throttle valve needle parameters, and main jet size all need to be re-engineered/ experimented to find proper mixture delivery.

[uksparky]

ok i just read another thread where twotired posted a cut out of a carb and i totally F'd up the air fuel screw

all the way in is all fuel



so originally with 1.5 turns, to lean it out i would turn it out 1.75 wouldnt i?

Turning out is rich......in lean.....got my carbs 2.5 out... perfecto 

[xsmooth69x]

The CB550's pilot circuit is a separate carb circuit with no control input from the twist grip.
The early carb's pilot circuit has an air control screw to regulate the air going the pilot jet's emulsion tube.  The resulting premix is delivered in its entirety to the carb bore at a rate variable with the vacuum presented at the pilot circuit exit port.  The vacuum intensity is greatest when the slide is at it's lowest point, and diminishes as the slide is raised.

Further, there are two types of pilot screw on the early Cb550 carbs, the F carbs have a solid tipped screw allowing for all the air to be blocked from pilot circuit premix.  The rest have a a hollow tipped and cross drilled tip screw, which limit the minimum amount of air premix to that of the cross drilled hole size.  This screw tip type effectively creates a lower limit to just how rich the idle mix can be adjusted via screw setting alone.   The pilot circuit air supply has a inlet jet (ahead of the pilot screw adjustment), which sets the limit on how much the circuit can be leaned with any given pilot jet size no matter how far out the screws is turned.  The practical limit of pilot screw adjustment outwards is about 5 full turns with rapidly diminishing effect beyond 3-4 turns outward.

The idle mix for these carbs is purposely rich in order to compensate for mixture starvation when the carb slide is raised, causing rapid vacuum loss in the carb throat and the resultant loss of fuel draw.  Therefore, in practice, the pilot circuit is adjusted to achieve predictable power advancement when the throttle is twisted up to one half of the remaining travel at any engine RPM and in any selected gear.

The book's printed settings only apply to the stock air induction and exhaust back pressure.  Any change to these components have more than a cosmetic effect to the machine's operation.  Pilot circuit, throttle valve needle parameters, and main jet size all need to be re-engineered/ experimented to find proper mixture delivery.

thank you for the long explanation of the carb screw.

so should i do the solder mod the wholes in my air fuels screw?

also what was the answer to the screw? all the way in is super rich and all the way out is super lean?

so if my bike is super rich i would screw it in right not back it out?

[xsmooth69x]

also any ideas with the vacuum drop on carb 3 only

[TwoTired]

so should i do the solder mod the wholes in my air fuels screw?

I don't see the point of that.

also what was the answer to the screw? all the way in is super rich and all the way out is super lean?

Wow, it's almost as if you read what wrote! 

so if my bike is super rich i would screw it in right not back it out?

And, then you write this, ignoring what I wrote completely.

Super rich at idle throttle position is normal and may even allow more than 1/2 throttle twist without an engine wheeze response.
The pilot screw has little effect on mixture above 1/4-1/3 of throttle travel.
"Super rich" above those settings means addressing the main jet and/or throttle valve needle.  Such is the price for pods and pipe mods.

also any ideas with the vacuum drop on carb 3 only

I already asked what you mean by "vacuum drop".  ...Which you seem to have ignored.   ...My turn.
I suppose I could ask if you have the vac line damper closed too much on #3, though.

From my point of view, a "vacuum drop" (needle goes toward zero) is normal behavior for all carbs when the slides are initially lifted.

[xsmooth69x]

so should i do the solder mod the wholes in my air fuels screw?

I don't see the point of that.

also what was the answer to the screw? all the way in is super rich and all the way out is super lean?

Wow, it's almost as if you read what wrote! 

so if my bike is super rich i would screw it in right not back it out?

And, then you write this, ignoring what I wrote completely.

Super rich at idle throttle position is normal and may even allow more than 1/2 throttle twist without an engine wheeze response.
The pilot screw has little effect on mixture above 1/4-1/3 of throttle travel.
"Super rich" above those settings means addressing the main jet and/or throttle valve needle.  Such is the price for pods and pipe mods.

also any ideas with the vacuum drop on carb 3 only

I already asked what you mean by "vacuum drop".  ...Which you seem to have ignored.   ...My turn.
I suppose I could ask if you have the vac line damper closed too much on #3, though.

From my point of view, a "vacuum drop" (needle goes toward zero) is normal behavior for all carbs when the slides are initially lifted.

the screw thing was confusing ok  i thought i understood then you wrote the write up which i thought you wrote because i didnt understand which confused me more.......

the line dampener is good i adjusted everything and switched the lines around thinking maybe it was the guage or dampner thing but the gauges that did work showed the same pressure drop on cylinder 3

i explained the vacuum drop with pictures at stuff

[xsmooth69x]

wow ok sorry about my initial post i was super ADHD.

i was trying to say initially where all the things i did after i noticed the wierdness (ill get back to that)

i pulled the plugs to do a compression test thinking that cylinder 3 was letting go. 120psi with the throttle completely open. so then i noticed that my plugs where black (aka too rich). Please correct me if im wrong but i thought screwing in the idle screw all the way down means its practically cutting off the fuel (all air little gas). then when you back it out your releasing more fuel (more fuel with air) so what i did was screw the screw all the way in and backed it out 1.25 turn (originally 1.5 turns)

now i fixed the super richness and tested the compression on cylinder #3
---
also on a side note the carbs are completely stock. i have my E clip set one step up from the bottom; example

        ---------------/-x-/-/-/--

^ so if that was the needle the x is where the clip is out of the 5 positions

---

also from what i understand what the gauge reads dosnt really matter. you just watch the needles. i dont have a pro grade sych gauges its a fleabay set

---

so i took my carbs completely apart when i was building my bike. now everything is put back together except i have no reference on the position of the BIG idle screw should be before starting the sync.

initially i started screwing in the BIG idle screw until it barely started to lift the rack. carb sync'd the bike then noticed that when the bike got warm i had no range to unscrew the BIG idle screw to drop the idle to the point the BIG idle screw didnt even touch the rack.

^ that's the prologue ^

soooooooooooo this time i decided to re sync my carbs slowly moving the BIG idle screw and adjusting the carb sliders until the BIG idle screw is now in the middle where i have the ability to move the BIG idle screw in either direction to adjust the idle either way.

after everything was lined up at 1000-1200 rpm or right before the bike would stall out. (the most precise and accurate time to adjust the carbs from what ive read)



i designated cylinder #1 as the master. (sitting on the bike the carb all the way the left or the carb with the choke on it) then moving left to right while sitting on the bike adjusted 2 3 4 to match #1 (master)

so the bike is idling nice and smooth. then when i apply some gas and bring it up 3k-4k the gauge for cylinder #3 falls toward the starting position of the gauges before there is vacuum. the rest of the gauges raise in the opposite direction of the starting position of the gauges evenly together.

^^^^^^ seeeeeeee

[TwoTired]

Regarding number three:

When the gauge needles approach Zero, it means there is little cylinder draw, or very easy/low restriction flow in the intake runners, making the pressure equalization to the outside reference easy.
If you trust the gauge's ability to report the truth, then the air path upstream of the vacuum tap point is restricting pressure equalization, which is making the needle deflect away from zero more than the others.

Check to see that the #3 slide is indeed lifting when the throttle is twisted, either via a removed top cover to see the slide actual lift or look into the carb bore intake side.  A closed or stuck "on" choke plate can cause the same gauge reading, as can an obstruction in the filter.  Look for something upstream of the gauge tap in point restricting air flow.

Alternately you can check the head pipe temps for even heat when the the throttle is held open enough to show that odd vacuum reading.  Assuming the gauge report is real, it's cylinder can't be making the power the others have, and the exhaust ought to be cooler by comparison.


Hopefully, you'll have better luck with our language barrier than I've had.
My approach is to teach you how it is supposed to work, so you can learn principles on how to fix things for a lifetime.  I feel if I just tell someone to tweak this or that screw, I believe one will simply learn dependency on others, or become more adept at ever creative ways to avoid true understanding of how machines are supposed to work.

[bollingball]

My approach is to teach you how it is supposed to work, so you can learn principles on how to fix things for a lifetime.  I feel if I just tell someone to tweak this or that screw, I believe one will simply learn dependency on others, or become more adept at ever creative ways to avoid true understanding of how machines are supposed to work.

Sad but true not a lot people think this way any more.
Ken

[xsmooth69x]

Regarding number three:

When the gauge needles approach Zero, it means there is little cylinder draw, or very easy/low restriction flow in the intake runners, making the pressure equalization to the outside reference easy.
If you trust the gauge's ability to report the truth, then the air path upstream of the vacuum tap point is restricting pressure equalization, which is making the needle deflect away from zero more than the others.

Check to see that the #3 slide is indeed lifting when the throttle is twisted, either via a removed top cover to see the slide actual lift or look into the carb bore intake side.  A closed or stuck "on" choke plate can cause the same gauge reading, as can an obstruction in the filter.  Look for something upstream of the gauge tap in point restricting air flow.

Alternately you can check the head pipe temps for even heat when the the throttle is held open enough to show that odd vacuum reading.  Assuming the gauge report is real, it's cylinder can't be making the power the others have, and the exhaust ought to be cooler by comparison.


Hopefully, you'll have better luck with our language barrier than I've had.
My approach is to teach you how it is supposed to work, so you can learn principles on how to fix things for a lifetime.  I feel if I just tell someone to tweak this or that screw, I believe one will simply learn dependency on others, or become more adept at ever creative ways to avoid true understanding of how machines are supposed to work.

ow don't get me wrong you information is invaluable and its rare these days to find people who have patience to take the time to explain things.

Im soooo going to pull that top off the carb!!! i never thought to look and see if that sticks!!!! filter is a K&N filter with the bracket so they all would be F'd up and really really look closely at the airbox rubber booootttttttssssssssss

[crazypj]

Could be the bolt holding operating arm to shaft has fallen out?
That would prevent slide lifting.
It would cause a high vacuum though, not low

[xsmooth69x]

Could be the bolt holding operating arm to shaft has fallen out?
That would prevent slide lifting.
It would cause a high vacuum though, not low

popped the top off and everything is moving fine.

sprayed WD-40 then tried starter fluid and no changes..... when i really open the throttle up then cylinder 3's vaccum raises and equalizes with the rest of them.

if a float i the float bowl getting stuck cause this? or maybe like the butterfly flap thing if it wasent all the way closed or open or not inline with the other flaps?

[Randy]

AAArrr. check to see if the tube going to the intake manifold on 3 is tight also.. those little rubber "O" rings will move out of position and at a high RPM.. I have simular problems..

[crazypj]

Things below the slide won't affect anything, unless someone put the emulsion tube in wrong and that is holding slide open
I've only ever seen it once, the needle was the only thing stopping the needle jet going into engine

[xsmooth69x]

ok i figured it out!!!

had to rip the carbs out!!! i hate taking them off its such a horrible process....

anyways in a nut shell for some reason the float in carb 3 was way way way lower than the 22mm its supposed to be. how did this happen i had no idea. when i rebuilt the carbs i checked triple checked and checked again

weird but ya thats what happened. so pretty much carb 3 was being starved. this made sense because when i really chopped the throttled it cylinder 3 vacuum would come back up to where the other carbs would be then after letting the throttle and bringing it up to speed it would again fall but chopping it would bring it back.

after i fixed the height all the vacuum needles are perfectly in sync.