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Discussion Starter #1
I acquired this bike last fall in non running condition and split the case over the winter to replace the oil pump. Now the bike is back together and running but has a bad vibration in the early throttle stages and smooths out when the throttle is opened further. I could use some help with understanding the problem and a solution. Here is what I've done so far:

1. Searched this forum to see what others have encountered with
vibration.
2. Crossed my fingers that I got the left hand balancer installed properly.
3. Someone of the forum suggested a fuel flow problem may be causing
the vibration. I decided to sync the carbs and found they were out of
sync and when I balanced the carbs, the engine sounds improved
noted by the increase in idle speed.
4. I checked the pilot screw setting on each carb and found them set at
3 1/4 turns out which seemed excessive. I expected 2 - 2 1/2.
5. With the engine warmed up and running at idle. I turned in each pilot
screw.
First on the right side carb, then on the left side carb. On the right
side carb, I was able to turn the pilot screw all the way in with
no change to the engine sound. I backed the screw out to it's original
setting, then repeated the process on the left hand side. On
the left hand side the idle began dropping as the screw was turned in.

So, it sounds like I have an issue with the right hand carb right? Does the pilot screw only come into play at the low throttle setting? Once past a certain point on the throttle, the needle jets come into play? Would that explain the vibration at low throttle and the smoothing out at the wider throttle setting?

When riding, I can cruise in 1st gear slowly putting along and no noticeable vibration. Once in 2nd, 3rd, or 4th, if I'm coasting in any of those gears and apply throttle, I get the vibration which is a fairly good shaking of the handlebars and gas tank, then it smooths out as the bike picks up speed and the RPMs come up. Even coasting at 50 MPH and apply throttle, I get the vibration, so it's not such as nice ride right now.

Thanks for your assistance, this forum is a great tool for vulcan owners.
 

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Sounds like it is only running on 1 cylinder at low rpm/throttle...that accounts for the vibration.

Something amiss with that right carb.
 

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Sounds like it is only running on 1 cylinder at low rpm/throttle...that accounts for the vibration.

Something amiss with that right carb.
Is it possible he just has a clogged pilot jet? It sounds like it runs fine at speed / under throttle but that cylinder dies at idle.
 
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