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Discussion Starter · #1 ·
I just synched the carbs on my '82 GL1100 using a Morgan Carbtune. I noticed that the gauge for #4 cylinder was pulsating/vibrating up and down while all the other cylinders were steady. Any ideas what would cause this?

Thanks
Brian
 

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Pulsating vacuum generally suggests a valve that's burned or not closing properly.
 

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Could just be a chunk of carbon in the valve seat. Run some Marvel Mystery Oil, or Seafoam in your gas, and use the "dribble in the carb" method on the can. Sometimes, it will burn off or blow out allowing the valve to seat better. Could also be that particular valve's lash is too tight. I had an old school mercury sync set in the 80's, and the adjustment valves were hard to get to stop all the pulsations. Let us know what you find? jimsjinx
 

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Discussion Starter · #4 ·
Thanks for the responses.

You guys may very well be right and I will go through the valve clearance check again. But I have set the valve clearances very recently and I ran a compression test very recently too. All cylinders had compression pressures within a PSI of each other at about 140 PSI.

I will check it out and report back.

Brian
 

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Having never seen a Morgan carbtune, I looked one up tonight and noticed that it didn't come with dampening valves that the 4 guage set does, they enable you to steady the needles when they are bouncing by about an "Hg or so up and down, just saying you might want to look into that before you start pulling it apart again, given that your compression test came out so well.

You might also want to check that your intake rubbers (the top ones, with the hose clips) are properly tightened, as well as the O rings at the bottom might be letting in enough air to make the needle (or column) jump around more than the others.
 

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try switching the gage on that cyclender.
It may be the gage or the orfice-restricter that limits the pulse action.
My set have a orfice pushed into the tubes.
 
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