Topic: Low/no vacuum pressure shown when sync carbs

[haill]

In the last stages of rebuilding. tried to sync my carbs #627b on 71 CB500 last night. the vacuum pressure was not reading on the Morgan carbtune tool. only showed when rev-ed motor and was coming back to idle.
Have completely rebuilt the carbs removed emulsion tubes boiled them in brake fluid and lemon juice & water. Bench sync'd them as described in forum.
What is the things to check for vacuum pressure. Will redo the valve clearance. Did it with the bike warm which might be an issue. the timing has been set using a light across the points. cam chain adjusted.
The bike runs rich. all the jets are stock #'s there is a new uni foam filter stock air box with a 4to1 exhaust. the air screw seems to do little if any in changing idle speed. they are set at 1 turn out.
Thanks for your time in advance.
regards Keith, Nova Scotia Canada

[mystic_1]

If the bike is running, then it's for sure producing vacuum.  I'm betting the issue is in your instrumentation.  Does the Morgan Carbtune have damper valves in the vacuum lines?  If so, open them up more.

mystic_1

[punch455]

Hey, the exact same thing happened to me after  rebuilding my carbs. I bench synced them, hooked them up, and put the carbtune on.  I started the engine and noticed that not even my #2 carb (the base non-adjustable carb on older models) was pulling a vacuum reading. I thought maybe my carbtune was bad! How could my engine not be creating vacuum?? However, I went ahead and started adjusting the carb slides anyway, just to see if there would be a change on the gauges. And sure enough, one by one they started popping up on the carbtune. What I thought was a pretty close bench sync, was still WAY OFF.  Hook your morgan back up, start the engine, and begin adjusting your slides.  You'll soon notice the reading on those vacuum gauges starting to rise. 
Good luck!

[haill]

thanks for your replies.
think i have a compression problem for squirted some oil down  the cylinder then realized that the compression gauge tester was a size to big. Sunday in rural Nova Scotia most stores are closed. put the plugs back in and the carbtune came to life when tried to restart. which until i can get the proper fitting for the compression gauge is my best guess. the bike shows 23,000km for a 1971 cb500. thought the engine was ok 
Maybe the engine will need doing. the plugs are soot covered every time i pull them and the bike is running very rich. the carbtune does not move at all even after turning the carb sync adjusting screws all the way in. Also removed the restrictor in the lines and tried with out. which leads me to think there is little or no compression.
the only time the gauge moves is coming down to idle after a quick rev. close but no cigar...