B screw not moving jockey wheel away from cassette

[el_Pedr0]

I've got an Exage 400LX rear derailleur and the jockey wheel is essentially running directly on top of the largest gear in the rear cassette, so I need to increase the gap.

Screwing in the B-screw seems to have no effect when the chain is on. The end of the screw is making contact with the frame, and so the tab on the derailleur through which the B-screw is threaded, does get pushed round. But the jockey wheel doesn't appear to get further away from the cassette. I have dismantled the knuckle, and cleaned and greased the internals. The action of the knuckle spring seems fine.

I think I might have also cleaned and greased the tension spring a few months ago - but can't really remember.

I recently replaced the chain. Replicating the number of links of the original chain. I've also checked using on online calculator and it comes up with the same number of links as I have on my chain.

I can't figure out what's going on. What am I missing here?

While there are no variable settings in the knuckle spring, I can't remember whether there was in the tension spring. Could a wrong setting on the tension spring inhibit the jockey wheel from moving away from the cassette?

 

[Paul R]

Is the mech designed to take the the size tooth of cassette you have? As if its not it can be hard to push them any further away sometimes a longer screw works but ofen it ends up at an aukward angle to the tab on the frame.

check the spring holes on the mech are in the right place too.

 

[el_Pedr0]

Is the mech designed to take the the size tooth of cassette you have? As if its not it can be hard to push them any further away sometimes a longer screw works but ofen it ends up at an aukward angle to the tab on the frame.

check the spring holes on the mech are in the right place too.

It's all the original kit that came on the bike when I bought it new so I assume that it is designed to go together. I haven't ridden it for 20 years, but I reckon I would have spotted it back then if it had been ill configured. So I think it used to be fine.

The other thing that cones to mind is that I replaced the cable and housing too. I wonder if I've cut the last stretch of housing too long. Could it be that the stiffness in the housing is pushing in such a way as to counteract the effect of the b screw?

 

[Paul R]

It should be ok. the screw is screwing in and not stripped i assume

 

[el_Pedr0]

check the spring holes on the mech are in the right place too.

What spring holes?Please could you describe where should I look .

 

[el_Pedr0]

It should be ok. the screw is screwing in and not stripped i assume

Yes. Working fine and moving the little tab round on the derailleur