Low fps could it be cylinder related?

[Colin Allen]

What’s the correct O ring size for the piston and cylinder head ?

Cylinder head is generally 22mm OD, 1.5mm cross section.
Piston head is generally 24mm OD, 2.4mm cross section

AK2M4 sells some slightly larger piston head O rings for slightly larger cylinders; they are 24mm OD, 2.7mm cross section.

 

[Pollynator_bravo2]

Cylinder head is generally 22mm OD, 1.5mm cross section.
Piston head is generally 24mm OD, 2.4mm cross section

AK2M4 sells some slightly larger piston head O rings for slightly larger cylinders; they are 24mm OD, 2.7mm cross section.

Epic thanks for this. Next job on the list ?

 

[Big Cheese]

Compression test the cylinder. With the cylinder out of GB with tappet and nozzle fitted. Hold finger over nozzle and push piston down into cylinder. It should stop 2/3 way down when all air is compressed. If it doesn't replace the piston oring.