Datsun Forklift with J15 engine-velocity governor

Can anyone help with the tube/vacuum connections on the velocity governor on the J15 engine.
I don’t know the history but it has not been having an even mixture across the cylinders and fouls up 2 spark plugs quickly (black sooty fuel type foul)
The outlets on the Velocity governor were hooked up to the air cleaner and carburettor, (2 outlets on the VG). It appears if I plug these 2 tubes that suddenly the spark plugs become the same colour.
It used to have LPG on it, and I suspect that things have been changed around after it was removed. Indeed there is extra things brazed into the air cleaner.
I don’t know whether I should just leave these two outlets plugged, or whether they really need be connected. I guessing that they don’t have anything to do with the governor function, or do they ?
Also if someone can point me in the direction of a free manual, that will be good. All the sites that I looked at wanted credit card details, or seemed dodgy. Cheers

The governor function is also regulated by a spring not entirely from vacuum.Check the governor butterfly below the carburettor. If the spring on it breaks, it shuts off most of the fuel to the engine and the air fuel ratios will be inconsistant ! It should be sprung wide open.I'd leave the 2 ports plugged as long as you have one induction port for the vaccum advance unit that should be hooked into the inlet manifold somewhere or near the carb base and the other larger port at base of carb leave connected. do not plug.

thanks, I will check more with those springs. Hopefully I’m getting near solving the problem. I have the vacuum advance connected to the port above the carburettor butterfly.

It should be below the butterfly

As otherwise there is never any vacuum.

cheers, Ill try it on vacuum advance on manifold vacuum. Its actually running pretty sweet now how it is. The port I’m using comes into action as soon as the butterfly starts to open, so it vacuum at light throttle, but not idle.

I posted yesterday as I didn’t know anything about velocity governors (and still don’t!) but was thinking that the ports on it had something to do with its operation. I think it just operates on spring pressure and a off centre butterfly that sucks closed at higher airspeed. I think the ports are only on it now to perform other duties, so it doesn’t matter if I block them off, although I’ll try the bottom port on the vacuum advance now and see how that goes.