Cold Cylinder Causes?

First some home made synch gauge back story:
I had followed a model which I found online and as it turns out, not everything on the internet is accurate. Go figure. So, instead of connecting all 4 tubes, I essentially bent two separate tubes, one for carbs 1 and 2, and the other for carbs 3 and 4 and put them on the board. It worked great, or at least according to my readings (which were also done exclusively online). It was a trick to tighten the securing nuts without throwing the synch out of line due to their sensitivity. Other than that, I really have no idea the amount of vacuum that my bike is pulling or is supposed to pull, or how to translate inches of Hg into inches of ATF. At this point I am really only confident that all carbs are pulling equal vacuum. Also, after tuning and a quick joy ride I decided to do the header touch test. All headers were screaming hot, except for #3. It was far to hot to hold your hand on but not as hot as the others. Any ideas regardings causes for this? Carbs were just rebuilt, all carb holders and boots replaced along with air filter. I did the carb float wet test and all levels are equal, plugs are new. Bike runs perfectly in all other respects. The only thing I can think of is pilot mixture screws. I have them set at standard 2 turns out. If the pilot screw for carb #3 is not rich enough, could that cause cooler combustion?

I would appreciate any help.
Thanks

Jon

did you go through the carbs?

Maybe not synchronized, like the throttle of the cold one is not open as much at idle. Could be problem in the pilot circuit inside the carb or adjustment of pilot screw(s).

I will do another check tonight as far as synch goes. Carbs should be tuned correctly, the only exception being pilot adjustment. Any idea at what level I should set the vacuum? I am using ATF not HG. Is there a conversion or estimation for ATF usage in replace of Hg?

Thanks
JOn

I don't have a sync gauge, I set mine by ear.

Do you hear the usual idle drop off as you turn the pilot screw in?

Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering. I set the pilot screws at two full turns out and then synched the carbs. It's possible that the pilot screw might be out for whatever reason and also possible that I bumped a synch adjustment screw/nut after synching. I will report when rectified.

Jon

Bet you any money you have an air leak.

Pull the carbs off and visualy inspect the throttle slides/butterflys. If you had equal vac on a guage/manometer, and your #3 bore is completely/almost closed entirely compared to others, then there is an air leak downstream throwing off the vacuum.

And this makes the cylinder not fire, yet register equal vacuum.

Seen it many times...

GL.

jonnygorman wrote:

Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering. I set the pilot screws at two full turns out and then synched the carbs. It's possible that the pilot screw might be out for whatever reason and also possible that I bumped a synch adjustment screw/nut after synching. I will report when rectified.

Jon

A change in vacuum corresponds to a change in mixture (either concentration or content), which corresponds to a change in cylinder power output thus you hear the change in rpms.

jonnygorman wrote:

Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering....

Bountyhunter has a twin cylinder KZ750.

Good Fortune!

jonnygorman wrote:

Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering. I set the pilot screws at two full turns out and then synched the carbs. It's possible that the pilot screw might be out for whatever reason and also possible that I bumped a synch adjustment screw/nut after synching. I will report when rectified.

Jon

I set my pilot screws about 2T out. Fully warm up bike, set to idle. Turn screw in until it just starts to drop off from being to lean (note position) back out until idle smooths out (note position) back out a little more until it gets too rich (it will start to run unevenly). Optimum setting is typically about 1/4 to 1/2T out from where it starts dropping lean. I fine tune in that range to get smoothest idle at highest RPM.

Go back and forth left side to right to get best settings.


NOTE: I bench sync the throttles first using the smooth end of a very thin drill bit to get an accurate butterfly opening position on each one.

Patton wrote:

jonnygorman wrote:

Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering....

Bountyhunter has a twin cylinder KZ750.

Good Fortune!

True, I never tried ear tweaking a four.