It will either be the weber 32 DFT, or the FORD VV.
If 32dft there will be a screw near the base sticking out with a small spring around it, screw clockwise to weaken, counter clockwise to richen.
If VV the screw goes pointing downwards at an angle and is in a recess.
Same richen weaken direction as above for DFT.
tabetha