Not a tandem mechanic, and having an issue adjusting the timing chain tension on my Burley Duet (2000ish I think). I've found and loosened the two allen bolts on the front BB shell, and I've tried tightening the chain tension using a Park Tool pin spanner (the green-handled one I think) inserted in the pinholes on the right side of the BB, but this does not seem to be tightening the chain tension...Am I doing this wrong? I can press on the chain to increase slack (once released), and I can rotate/push the crankarms forward to take some of the play out of the chain, but there still seems to be more than 2" of play in the chain at it's tightest through a rotation of the cranks (i.e. this is the best it gets).

Thanks,
LKW

If you've got the fat part of the eccentric spun all the way to the back of the bb shell (i.e. the bb spindle is as far forward as it can go) and you're still have 2" of slack, your chain is too long.

Are you actually spinning the eccentric in the shell?

I will need to get someone sighted to let me know... Blind and can't feel if the eccentric is as you describe. I can feel the BB move backwards when loosened and by pushing/rotating the cranks I can achieve the original 2"+ slack. I honestly didn't try to slacken the chain with the pin spanner, are these pinholes on the side (located between the shell and the BB axle) the proper location to move the eccentric and remove the slack?

Thanks,
LKW

Try removing a few links from your chain.
CJ

If when your BB is fully forward you still have too much slack, your chain is too long. Put the BB in the rearmost position and remove as many links as possible, then move the BB forward.

If you are having trouble getting the eccentric to rotate, try a stronger pin spanner.

Another way to tighten the crossover chain is to 'float' as chainring dead center between top and bottom of chain. Chainring needs to be one or 2 teeth larger than the cross over rings are. Yes, the chainring will 'float' and stay in place. Tightens the chain and makes for a great conversation starter!
Just an alternative . .

While I will probably go with removing a link or two, I honestly haven't checked/noticed the tension problem since the last replacement and it cold have been measured wrong...I'm hyped about that floating ring thing! I'm thinking some sort of flourecent or obnoxiously bright paint or perhaps rigging a battery and some LEDs...

Sometimes referred to as a 'ghost ring'.