So I have found that poly string on my Duncan Butterfly works really well with plenty of tension, otherwise, it does not return consistently. I have also double looped the string around the axle.
However, with such strong tension, how is it possible to land kick flips? I find that by the time the yoyo comes around again, there are a few twists in the loop, ruining the trick.
Is there a solution to this problem?
In my experience neutral string tension is pretty much required for kickflips. I think you want to find a setup where the yo-yo returns consistently with neutral string tension (after breaking in the string).
I’m surprised double loop doesn’t get you consistent returns with neutral string tension. You might want to try some thick cotton. I dislike using the Duncan Butterfly. Not sure how well the string breaks in with the metal axle. It’s possible that you can apply a substance to the string to get it to respond; I don’t know what.
I use Kitty Fat in my butterfly’s, no need to have a lot of tension. However, Butterfly’s these days are not very consistent. They’re fun to get that way though. My favorites are the old glitter Butterfly’s (they pop up on ebay from time to time). But out of the new easy to find Butterfly’s they can be hit or miss. I bought all of my nieces and my nephew Butterfly’s last year. My one niece opened hers and I played it first and it was probably the best Butterfly I’d ever played! Part of me wanted to keep it 
I’ve found that by swapping halves sometimes you can get a really good playing “new” Butterfly. One of my daily players is a half Blue, half Orange. When it was just Blue the gap was HUGE. For whatever reason, it was perfect with the orange half. So maybe you’ve got one with the gap too large.
But as far as kickflips, need neutral tension. With Fixed Axle, after awhile, it’ll become second nature to get your tension where you want it.
Have you taken a look at Ed’s tutorials here: http://yoyoexpert.com/learn/#FixedAxle
Also, Ed and Drew had an awesome Fixed Axle Friday feature on YoYoNews that I highly suggest going through (Hey Ed, Drew, Steve and Andre bring that feature back please ;D ): http://yoyonews.com/category/fixed-friday/
Thanks. How do the wooden butterflies perform? Any better than the plastic ones?
The two wooden butterflies I’ve played have both been surprisingly good. Small sample size, but they played nicely. Be warned though, they are a little light.
Another question, are all olasic butterflies wonky? I mean, mine came brand new and the halves aren’t completely parallel with each other. Is this normal for a butterfly?
Yes Ed, Drew, Steve, and Andre, please do.
With the plastic Butterfly’s the axle eats through cotton. I prefer using the late 60’s two-tone Butterfly. The gap is wider than the earlier sparkle wood and to me it is a more consistent throw. Also you can often find an inexpensive one on ebay.
Yeah, the quality can be hit or miss on these. Ya get what ya pay for.
That is why I mentioned the two-tone 60’s model. It is a touch heaver and more constant. I have 3 of them purchased at different times from different sellers and they are all good.