Clicking on crank side downstroke

Question
Greetings!  I have been riding an old Motobecane Super Mirage for years now and have recently been doing some minor upgrades to it.  I had a chain that was skipping in the very highest gear.  I replaced the chain and freewheel (5 speed Suntour) which corrected the problem.  I also had a spare Shimano 600 rear derailleur that I'd been meaning to install so took the time to replace the derailleur and cabling.  Since then, it's been riding very nicely with the exception of a barely noticable "click" in the stroke.  You can't hear it but you can certainly feel it if you pay close attention.  It happens only on the downstroke on the right side, usually around the 2 o'clock position.  At first, I thought it might simply be slack in my stroke, but ruled that out.  I noticed that if I didn't apply pressure on the downstroke but instead waited until near the bottom of the cycle, it happened there.  I've checked my pedals and crank for loose bolts and I don't see a notable wiggle in the crank but bottom bracket seems the only other idea that comes to me.  Am I missing something obvious?

Answer
Wolf,

I have been thinking about this one.  You have hit the usual culprits, which are the pedal and the bottom bracket.  However, the fact that it repeats on every pedal stroke definitely says that it isn't in the rear drive train because the click would occur at different times depending on the gear.  Two things come to mind:

1.  Very often a square taper bottom bracket spindle gets loose from being tightened over the years and the crankarm ultimately expands too much to tighten further, stays loose and clicks when you apply your downstroke.  It is possible that is the problem.  The only solution for that is a new crankarm and possibly bottom bracket.

2.  The other possibility is that the adjustment rings ("bottom bracket cups") that hold the bottom bracket to the frame have loosened, allowing the bottom bracket to move, ever so microscopically, each time you push down on the pedal.  

Number one is a very expensive fix and number two is very cheap.  However, the chance is good that you don't have the wrenches required to  tighten the bottom bracket cups yourself, so my recommendation is that you take the bike to your local bike shop and let them have a look at it.  Don't tell them to replace anything, just see if they can first see if the BB cups can be tightened.  If they tighten them and the click still happens, then you may have to replace, but at least try tightening the cups first.

Hopefully this helps.  Good luck.

Graeme