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Vibration's got me worried.

  • Thread starter Thread starter Rocketjock
  • Start date Start date
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Rocketjock

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As I was saying in my 'Dies at the Stoplight' thread, I was riding along waiting for the engine to warm up and reaching down to feel the float bowls for warmth when I definately felt a good vibration coming thru the bowl from no.1 cylinder. Subsequent feeling of the other carb bowls revealed no such vibration. I thought it vibrated a little more than other GSs I have owned and this proves it. Any thoughts on this? Worst case scenario would be a sloppy rod, I guess. Is ther a simple way to check for such a problem? When I adjusted the valves I noticed excessive grooving wear on no.2 exhaust cam on no.1 cylinder. What could have caused this I have no idea. All other cams were fine.
 
Rocketjock said:
Care to elaborate?
Like Lynn says, a poor carb synch can cause vibrations. Other things can too of course.
Different vacuum in each cylinder will draw different amounts of fuel from the carb jets. The mixtures will be uneven. Combustion will be different between cylinders. The cylinders will be "fighting" each other in a sense.
Getting the cylinders to draw the same, or vary close to the same vacuum is important.
Valve clearances and ignition/timing must be correct before any carb synch. Also, mixture screws are to be adjusted correctly.
If it still vibrates, try re-torquing all motor mounts. Check the carb clamps too.
If it still vibrates, something else is wrong.
 
KEITH KRAUSE said:
Like Lynn says, a poor carb synch can cause vibrations. Other things can too of course.
Different vacuum in each cylinder will draw different amounts of fuel from the carb jets. The mixtures will be uneven. Combustion will be different between cylinders. The cylinders will be "fighting" each other in a sense.
Getting the cylinders to draw the same, or vary close to the same vacuum is important.
Valve clearances and ignition/timing must be correct before any carb synch. Also, mixture screws are to be adjusted correctly.
If it still vibrates, try re-torquing all motor mounts. Check the carb clamps too.
If it still vibrates, something else is wrong.

Altho I have had the carbs synced before, I guess I should get it checked just to rule that out. I'm a bit doubtful. There is no sign of vibration coming thru any of the other carbs. Just no. 1. As if that ol piston is goin bang, bang, bang.
Actually looked to purchase a sync gauge. Didn't find one for four cylinders. Suppose I could make one up with four glass tubes, twodrilled out aluminium billets, ball bearings and some tubing.
 
Motion Pro makes an inexpensive (about $40) mercury vacuum tool that works as well as the operator. I've owned one for many years.
If it's just the carb vibrating, it's possibly a loose clamp or something like you said.
 
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