I've been asked to inspect and fix someone's bike. Its a heavy full-suspension Kona "Stab Deluxe" downhill monster from 2006.
The main fault is that the chain gets stuck between the front chainring and the chainguide.
It is a single 36 tooth chainring branded as Saint, with Hussefelt cranks and a 4 bolt Truvativ crank. Not sure what the BB is other than external. Seems to be stock/original components.
There's also a trailing lifter wheel vaguely like a jockey wheel but without teeth, so seems to be a tensioner but has no tension, perhaps best described as a keeper?
My gut feeling is that the whole mounting bracket should not rotate like this. From below I can see threads of the external cup (?) housing between the BB case and the chain keeper's support plate.
There is a lot of scoring and worn-off plastic inside the chain guide itself, suggests this has been loose or wrong for a long time.
Question What's wrong with this setup? And how do I fix it?