Cota 330 rear shocks

[dirtydalesman]

Evening all. Went out for a play on the Montesa yesterday and one of the rear shocks cried enough. My dad got these with it in 1986. Presumably swapped to the ones on it because the valve parted company on one and the oil escaped. I haven't seen shocks like these before. Are the valves just for oil, or do you pressurise with air as well?

[feetupfun]

2 hours ago, dirtydalesman said:

Evening all. Went out for a play on the Montesa yesterday and one of the rear shocks cried enough. My dad got these with it in 1986. Presumably swapped to the ones on it because the valve parted company on one and the oil escaped. I haven't seen shocks like these before. Are the valves just for oil, or do you pressurise with air as well?

They look like early Falcons. The valves are there to allow them to be pressurised with gas. They need to have gas pressure inside to work properly.

[dirtydalesman]

I thought that initially, but I thought usually the gas sits the other side of a floating piston, separate to the oil. That hole is direct to the oil chamber. I have filled it with oil and blanked the hole, seems to work as the other one. But then I'm a bit lost as to why there would then be an air valve? 

[feetupfun]

3 hours ago, dirtydalesman said:

I thought that initially, but I thought usually the gas sits the other side of a floating piston, separate to the oil. That hole is direct to the oil chamber. I have filled it with oil and blanked the hole, seems to work as the other one. But then I'm a bit lost as to why there would then be an air valve? 

Yes that's true. Many shocks do have a floating piston to separate the oil and gas.

Standard Falcon shocks don't have a floating piston or a bladder or a piece of closed-cell foam. The oil and gas mix.

[dirtydalesman]

Ah ok then, that explains it. There is no gas left in the non broken one either, so I guess I just run them as oil shocks for now. They seem to be working ok.

[woody]

9 hours ago, dirtydalesman said:

Ah ok then, that explains it. There is no gas left in the non broken one either, so I guess I just run them as oil shocks for now. They seem to be working ok.

The handy thing with the Falcons having no oil / gas separator is that you can drain and fill oil through the hole in the body with the valve removed. You can use air, you don't really need nitrogen on a trials shock, around 50-70psi with a mountain bike suspension pump.  They'yy work better pressurised as it helps suspension preload and return

[dr nosh]

Pressurize with a high pressure, low volume hand pump as used on MTB forks and some MTB shocks.

[dirtydalesman]

Thanks chaps. I emailed Falcon and they were very helpful with correct oil volume and air pressure. I have pressurised as best I can with an airline regulated to the correct pressure, so I kept the trigger pulled as I released the inflator, hopefully not loosing too much air. The other side still has some pressure in, so I won't risk topping that up for now in case I make it worse! If they hold together for a trial on Wednesday, I'll get hold of a proper pump and set the pressure better.