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Discussion Starter #1 (Edited)
I've noticed that it is a nearly universal mod on EU spec V 650s to install a tube between the balance ports on the throttle bodies in order to address the sloppy low rpm throttle response (that is apparently quite bad on EU bikes), does this also work on US spec bikes or are we better off just shelling out for the expense of having the throttle bodies balanced? I have noticed that the on/off throttle response on 1st gen V650s is quite abrupt and is enough to unsettle the bike while leaned over, especially on sweepers where the throttle is being feathered a bit through the turn.

I would like to try to smooth out the on/off throttle response a bit, it is actually a new thing for me as both my previous bikes were carbed (CX500 and Bandit 600) and at least in my experience carbed bikes tend to be much smoother at low rpms (I test rode a Z650 which was only slightly less choppy and a Z900 which was actually buttery smooth).
 

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The Versys, as all bikes that have multiple carbs or throttle bodies do, has a mechanism to sync the throttle bodies. You are subverting that mechanism by linking the throttle bodies. While this may slightly tame an engine that is grossly out of sync it will not make it as smooth running as it could be if you understand how the intake system works.

As the intake valves wear one cylinder may suck in slightly more air/fuel than the other, due to better intake and exhaust valve sealing, causing one cylinder to have a greater power pulse than the other. The syncing process compensates for this by restricting the intake on one side more than the other smoothing things out and balancing the volume of air/fuel in each cylinder. Because the Versys has an uneven firing order, 0, 180, 720 degrees attaching the throttle bodies together will subvert this - the second intake stroke, which closely follows the first will be negatively impacted by the vacuum in the first throttle body, if you join the throttle bodies together. The engineers who designed the engine knew what they were doing.

If you want smooth running engine get hold of a sync gauge and sync your throttle bodies as the service manual describes. Ideally it is best to do this once a season or every time you change your oil every 12K km/7200 miles. It is critically important to do immediately after a valve clearance adjustment.
 

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Gen 3 throttle

When I got my Gen 3 650 I posted that it did NOT like being operated below 4,000 rpm UNLIKE my two Gen 1s which 'pulled' from 2,500 rpm in 6th.

I just turned over 50,000 kms on the GREEN HORNET TOO, and I have to say that it SEEMS to pull MUCH better at the lower rpm than it did when new (I DID just adjust my valves)....

:thumb: - :thumb:
 
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