clonk from the crank

[shimano]

I have a psuedo MTB, you know the things, oversize tubes, chunky tyres and cheapo components, even a big SHIMANO sticker. It does for me 'cos I'm skint and the chunky frame doesn't bend under my weight. However, recently I've noticed that even if I slacken off that ring thing and tighten that oblong nut thing ('scuse the technical speak) next to the left hand crank, after about 15 miles or so I start to feel then hear a clonk as the right hand crank reaches '12o'clock' I'm guessing worn bearings or maybe just needs re-greased. The question is if I completely undo yon oblong nut thing does that mean the entire crank/axle is free to come out to the right (with the LHS crank off of course) ?

 

[tdr1nka]

The simple answer is yes.
As for the clunk, it could be that the 'oblong nut' is working loose(the ring with the gaps round is for locking the nut into place and stop it working back out when you pedal)or that you have heavily worn, crushed or even missing bearings.

 

[shimano]

yeah , sorry should have said I did tighten my ring afterwards. hmmm maybe i should rephrase that...

 

[tdr1nka]

One other thought, are you sure the clunk is coming from the crank and not the pedal?