I have a pair of Betor 4885 shocks fitted to my fantic 200 I am trying to change the oil but cannot get them to damp in both dirrections without a half inch of free play first, any tips ?

Bin them,and get some Falcons,Rockshocks or NJB's.

Love too but the wife says no

Christmas is close.... Or just order them and dont tell her !

sounds like a stupid question, but are you testing them the right way up?

Also do you have the correct amount of oil in them ?

Am I testing them the correct way up? - Dunno, I have them chrome rode coming out of the top or chrome rod at the top to put it another way.

Have I got enough oil in them - Dunno the answer to that either. There must be an air gap to allow for the rod displacment? or is it trial and error? keep adding a few drops until I reach hydraulic lock? or maybe it will damp in both directions before then? to allow for expansion of the oil?

The seals are a bit shot, I have tried the brake fluid solution which has at least dramatically slowed the leak down. I am now packing an o'ring around the outside of the seal to reduce the seal bore diameter when all assembled, quite confident this will help. if not its out with the lathe to make up some new seal heads.

By the way, I dont take trials all that seriously, its just a cheap day away from the wife and kids.

are new seals not available......shurely they can't be too expensive???

First off test the damping with the chrome rod at the bottom. If the damping works nicely that way, you have enough oil in them already. If damping is lost completely when the chrome rod is at the bottom, then you need to add more oil and run them chrome rod up position.

The air gap is needed to allow for the volume of the rod going inside as they compress. 12mm shaft x 100mm travel = 11.3 ml. I would leave about 10 shaft volumes of air space = 113 ml of air space. If your shaft is only 10mm diameter, then about 80ml of air space should be OK.

Chrome rod at the top and a drop more brake fluid (dot 4) and all is good.

Some shocks have no separate air chamber (emulsified type i think) and actually work by foaming the damping oil. Perhaps this is what the shocks are - have you contacted Betor or the importers?

Interesting, so they get better the more use they have?

My betors are quite simple, they have a small diameter piston and piston ring with reed valve fitted either side. This all runs inside a tube installed inside the main body of the shock. I imagine the outside of the tube is that air storage area.