Hard starting XL1200 Wave Runner

I have a 1998 Yamaha XL1200 Wave Runner. It is stock.  I am unable to start unless loosen the gas cap and allow the pressure to out of gas tank. This pressure/vacuum problem exists mostly when the gas tank is full. After loosening the gas cap it is still hard to start. Once started and run,  it will restart for the rest of the day. Would I benefit  from installing a primer kit on the three carburetors? Would I have to remove the choke plates in the carburetors if I were to install the primer kit?
Pedro

Hi Pedro,
 On the Yamaha XL 1200, the fuel problem you have can be with the check valves or a restriction. But first you should fix the choke or install a primer kit if the choke can not be adjusted to close all the way. They must close all the way to work.
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