You can use a 2 inch by 1/4 inch flat bar with a hole just small enough not to let the spring slip through. Bring each cylinder up to TDC (top Dead Centre) then with a deep socket on top of the valve hit the spring down with a hammer the colletts will jump out. Replace the oil seal and then rebuild the spring etc. This is were the flat bar comes in compress the spring with the flat bar and whilst doing this get a mate to fit the collets. Then move onto the other cylinders. It can be a bit of a fiddley job and you do need a good push down on the flat bar.
Good luck 819
