Need help with Vibrations post 4.5K RPMS

[StefanOnHisS10]

I don't ever remember reading about vibration(s) stemming from the carb. Does that mean that bikes have become smooth enough that we now feel it?

I invite you to ride my DR800!
It runs a 100% perfect but can rearrange one’s balls pretty good at low rpm

 

[Sierra1]

Again . . . . thump, thump, thump.

 

[StefanOnHisS10]

Yes indeed!

 

[WJBertrand]

The S10 throttle bodies share a common shaft, so the butterflies are fixed with respect to each other. The synch on our bikes is just an air bypass adjustment.

OK, that makes sense and is a popular way to do it these days for parallel cylinders. Another common way (for both carbs and TBs) is to have a precise air bypass gap around the butterfly and the sync procedure adjusts that gap by moving the butterflies relative to one anther to match each other. As long as we're talking about different ways to sync, my RD350 had manual slides with a split cable pulling up on each slide. You would synch that one by adjusting the cables until the slides had equal air bypass. Same ideas, and true for either carburetors or TBs. I'm not sure exactly which way they do in in V-Type engines where fixing the TB butterflies to the same shaft is not possible.

 

[holligl]

I installed pigtails to stay in place, making it quicker and easier to synch more frequently.

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