Effects of pinched Tank Vacuum pipes....

[Tubz1983]

Curious as to the effects on the engine when having pinched fuel tank Vacuum pipes? And how to create a straight route from the tank base to the floor with causing this issue?

[darrsi]

Engine will just run rough then most likely eventually cut out if they're properly kinked.

[BBROWN1664]

If the pipes are kinked, you will get a vacuum build up in the tank.

Best case scenario is that the bike will cut out and refuse to restart for a while as the fuel pump cannot suck the fuel out of the tank anymore. Opening the fuel filler cap (slowly) will let air back in to the tank and the bike will restart with a bit of persuasion.
Worst case, the vacuum will cause the tank to get sucked inwards deforming the tank and then the bike will cut out and refuse to restart for a while as the fuel pump cannot suck the fuel out of the tank anymore.

To avoid the issue, gently pull the pipes downwards from behind the carbs as you lower the tank to keep the pipes unkinked.