O.K. I tried to idle my Coker. I’m finding it very difficult.
I idle my 20" with the right pedal down, going pack and forth between “bottom dead center”.
Is this the way to idle a Coker, or should you go back and forth between the cranks parallel to the ground.
Thanks.
Either way works, though I personally can only do the normal idle, not the circus idle. The longer the cranks, the easier Coker idling is. However, the main thing is: practice, practice, practice. 
Put on the longest cranks you can find if you want to make it noticably easier.
The technique that I use for coker idling is different than the one I use to idle a normal uni. With a normal uni it is very easy to keep the wheel moving back and forth in about 25% of the circumference. Often times I probably use 10%. On the coker I have to use around 35%.
Basically push the wheel backwards and then as soon as your cranks pass vertical start slowing the wheel. It will take some time to bring to a full stop. Be sure not to stop the wheel in a position where you will have no leverage for the next downstroke. That is, make sure you will be able to get enough power to stop the wheel then reverse it. Coker idling looks a lot slower.
It;s a change of emphasis. On a 20, you can dictate the speed of the idle. You can idle gently or aggressively, fast or slow, within certain broad limits.
On a larger wheel, and especially a Coker, it is more like riding from one position to another, pausing, and riding back.
The idle has two “poles”:
If you try too hard to dictate to the Coker, you will give it too much momentum, and it will be difficult to stop it at the other end of the pendulum swing.
Look at a distant object.
Relax.
Don’t hold the seat.
Obieone the truth speaks here. Try starting with a super idle (full revloutions of the wheel) to get the feel of changing directions. S-L-O-W-L-Y. Keep your weight on the seat. I have not tried circus idle but can idle if I am slow and use alot of the tire revolution. This requires a big area.
It also helps to have maximum air pressure in the tyre.
What’s a circus idle?
The cranks do not cross the bottom most position. They stay in a relatively horizontal position. The motion in circus idle is done by varying the cranks about the 3 and 9 o’clock positions. Regular idling is done by varying the cranks about the 6 and 12 o’clock positions.
Do it like this
I find you use your top foot to control the idle more than on a normal sized uni.
Joe
Wow, I’d never have thought that idling up an almost vertical wall would make things easier 
STM
I can idle a Coker if the cranks are long enough. The TCUC club Coker has six-inch cranks on it, and I can idle it one-footed (only with my right foot though) and have managed to mount into one-footed idle just to prove that I could do it. Idling a Coker with shorter cranks in any way is very difficult for me.
Idling a 24" uni is like, “Hmm. Hmm. Hmm. Hmm.”
Idling a Coker is like, “URGGHH!! URGGHH!! URGGHH!! URGGHH!!”
That’s the only way I can describe it myself.
I haven’t tried a Coker yet but, I found the difficulty increased significantly trying to idle on my 29er (compared to my 24). What worked for me was tightening up the pedal strokes on the 29er to reduce, or more accurately arrest, the greater momentum of the wheel. On my 24 I tend to idle with my foot going from about the 8 o’clock position to the 4 o’clock position, 8 to 4, 8 to 4. On the 29er I’ve found it easier to go from about 7 to 5, 7 to 5. Maybe the reason I do it this way is because I’ve always tried to keep the rhythm of the idle about the same. Maybe I’ll try slowing it down a bit as others here have suggested.
Funny, I’ve only ridden a coker for maybe ten minutes, and I could idle and ride backward first try, no problem. It did feel very akward, but I could still do it, although a little wobbly. It had 150’s I think. The trick I guess is to hold yourself back, be ready for the transition from forward to backward idle, so it doesn’t through you off.
I had a coker for a while, until evan took it back. It had 110 cranks and I couldn’t idle it at all. I would do the backwards rev and the short cranks just made it slip out right away. I couldn’t put enough force on it to make it go forwards again. So I guess what everyone says about long cranks is right.