Flat Spot in the Rev Range

Took the bike, 86 vfr 700, out for a shake down ride in the canyons after I have been building it over this last winter. Everything is pretty good except a flat spot in the rev range. It is very noticable when getting back on the throttle coming out of turn after trailing throttle into the turn. Happens between 4000 and 7000 rpm and about 1/3 to 2/3 throttle opening.

I believe that should make it the needle and needle jet at this point in the throttle opening.

Jetting is stock, carbs are beyond cleaned, sync'd, etc... It has a 4-1 Kerker pipe a Delkevic carbon can. if that makes any difference.

Anyone have any ideas?

 

It's the exhaust. Exhaust + carbs.

I've had similar on one bike when i switched over from stock setup to Kerker 4 into 1.

You'll need to experiment with washers to lift the needle (don't change mainjet) until problem goes away or is minimized.

Something else you could try is adjusting the floats to a 1mm lower setting ( upside down) in order to raise the fuel level in carbs for richer midrange.

 

+1 What Squirrel said, with stock it seems (at least on my 750's) I feel a flat spot around 6,000 to a little under 7,000, then it is off to the races.
Change your exhaust from stock and that flat spot only gets larger until you make jetting/needle adjustments.