I have a similar query as yours.
I Got My TB350 BS 4 Delivered Recently On 23rd June 2017.
During Delivery, The RE Mechanic Explained Certain DO's And DONT's With One Of Them About Being The Built Of Air Inside The Fuel Tank.
Issue: Air Build Up In The Tank On Being Kept Idle In The Sun Or Anywhere For More Than 3-4 Hours. Before You Start Your Bike, You Have To Open The Fuel Lid And Let The Air Escape.
Reason (Given By RE Mechanic): Certain Changes Were Made To Fix Leakage Issues In This model (The EVAP system as explained above) . As A Side Effect, The Air Evaporating From The Petrol Locks And Builds Up Inside The Tank. The Fuel Lid Has To Be Opened To Let The Air Escape Before You Resume Riding.
My Investigation: 1) I Have Noticed Air Escaping The Fuel Lid When The Above Scenario Happens. A Couple Of Times, The Air Escapes Such Vigorously That There Is Also A Loud Sound Generated With It.
2) When I Keep The Bike On Side Stand For Some Time, On Resuming Back The Ride, The Bike Stops After Some Time. It Stops In A Way Like The One We Experience When The Bike Goes Into Reserve. On A High Level, It Seems That The Bike Is Not Getting Any Fuel Intake. In Such Cases, I Open The Fuel Lid, Let The Air Escape And Then The Bike Starts Effortlessly.
Other Issues: Due To Above Explained Issue, The RE Mechanic Asked Me To Fill Only 10 L Of Fuel At Max So That When The Air Escapes, The Fuel Does Not Gushes Out With It. He Also Told Me That The Bike Has Only 16 L Of Fuel Capacity As Opposed To The Official Stat Of 20 L.
Over The Internet, I Did Not Find Any Stories Of Similar Issue apart from this thread. I thought the issue was with my bike individually.
Has anyone tried filling the tank up to the brim and faced any issues with the BS4 model? Also, anyone facing stalling issues with the bike when kept on side stand for sometime? Thanks in advance.