of carb sync and pilot jet adjustments?

Need help. I'm obviously, not capable of figuring this out on my own.

I have two carburetor racks. One is original equipment, the other one from eBay.
I have cleaned both numerous times using the scotch tool, syringes, compressed air.

The best I can tell, all passages are open, including the pilot jet transfer, the ones that run at a 45° angle to the pilot jet from the bottom of the emulsifier fire tube.


Having said all that, I still don't have any real adjustment, if any when adjusting the pilot jets.

I have had both racks on and off at least a half dozen times now.

One lucky time, everything worked great! Every pilot jet had adjustment, the engine would stumble when closed, and in RPM would pick up when the chat was open to about 2 3/4 turns.
I removed the carburetors to see where the butterfly valves were when the bike was adjusted and running great.

Here's a short video.


Me, not good enough to leave alone, decided to replace the OEM diaphragm on this working rack, and also to change out the float bowls with 1980 screw type drain instead of 1979 remove the bolt type.
In hindsight, WTF was I thinking? "If I could only get it back to where it was when I started, I'd be happy!" 

Did the bench synchronization, installed on bike.
The synchronization was close on the running bike, made some minor adjustments within factory service manual specs.

Went to adjust the pilot jets and now none of them, none, have any impact on the engine performance across the entire adjustable range.

In a earlier post, scotch was nice enough to reply and provide insight about the difference in vacuum levels between the engine side of the butterfly, and the air box side of the butterfly. If I understand it correctly, the engine site has much more vacuum for running the needle, jet and main jet. This value is measured in inches of mercury. The other side, of the butterfly, which creates a siphoning effect is what provides the pilot jet circuit with fuel.

Finally to my question, is it possible I have the synchronization incorrectly set, which is preventing adequate inches of water vacuum to enable the pilot jet circuit to provide fuel? I know that the air passages are clear and open as proven by spraying wd40 from the pilot jet and can see it escaping from the inlet passage at carb mouth, air box side. IIRC, the bottom hole.

At this point, the bike is running great, idles smooth and nice and has beautiful response from idle to redline, so I am reluctant to mess with them much more. Even at that, I'm very curious about why that one time I had pilot jet response across all six, other times I've had four out of six or five out of six, and now, zero out of six???

Short video of current running condition..


Hoping for responses.. sorry to bother everyone yet again...







 

Let me ask the stupid question of the day.

For perfect synchronization of the carburetors, shouldn't the air filter be mounted?

"For perfect synchronization of the carburetors, shouldn't the air filter be mounted? "

Irrelevant !

First,  having the air filter in or not is irrelevant . it has no effect on the idle circuit. the only time the air filter becomes relevant is at maximum rpm if the air filter does not pass as much air as the engine requires, the air filter can cause a richer mixture due to a vacuum in the main throttle bore.

Did you go and buy an aftermarket carb rebuild kits and then swap out the parts?/What may be happening here is that the springs on the pilot air needles are coil bound when you close the needles and are not fully allowing the needles to seat  in the needle orifices so the pilots are actually open.

I keep harping on fit form and function. Replacing parts with aftermarket parts have to meet Fit, Form and Function. If any dimension is off on the replacement part for the original part, how do you know that it will work???

I'm dead set against buying "carb rebuild kits" The only thing that needs to be replaced are the O-rings on the float needle seats and a carb bowl gasket. Everything else can be cleaned and returned to service. The emulsion tubes, pilot needles, main jets and pilot jets can all be cleaned and polished with Autosol (metal polish)

 

Kawboy wrote:

First,  having the air filter in or not is irrelevant . it has no effect on the idle circuit. the only time the air filter becomes relevant is at maximum rpm if the air filter does not pass as much air as the engine requires, the air filter can cause a richer mixture due to a vacuum in the main throttle bore.
Fully agree.

Did you go and buy an aftermarket carb rebuild kits and then swap out the parts?/
Yes. WiredGeorge used what appears to be a Damen-Ding kit.

What may be happening here is that the springs on the pilot air needles are coil bound when you close the needles and are not fully allowing the needles to seat  in the needle orifices so the pilots are actually open.
Interesting idea. If I was to remove the spring and run the needle all the way down would that prove or disprove the theory?

I keep harping on fit form and function. Replacing parts with aftermarket parts have to meet Fit, Form and Function. If any dimension is off on the replacement part for the original part, how do you know that it will work???
I bought DD kits and currently have that kit installed in both racks.  I also have a Keyster kit. I'll measure each..
Come to think of it, I also have an OEM carb that I can remove the spring to get a baseline length measurement then compare.

I'm dead set against buying "carb rebuild kits" The only thing that needs to be replaced are the O-rings on the float needle seats and a carb bowl gasket. Everything else can be cleaned and returned to service. The emulsion tubes, pilot needles, main jets and pilot jets can all be cleaned and polished with Autosol (metal polish)
Unfortunately, that option no longer exists for me.

 

Thank you for the help Gents!

I think I will quit now. Five of the six pilot circuits are operational. Cylinder number four has minimal impact on engine performance. But the synchronization is good. Throttle response is great.

I do not remember this motorcycle running so good, ever.

So I am going to stop while I am ahead.

This will allow me to work on some unmolested KZ 1300s that are in the wings waiting their turn on the lift.