Broken 3 12ga spokes using a Manic Mechanic Adapter..How to fix??

I've got a wheel from my local bike shop that supposedly more heavily built with 12ga spokes coster brake arm says HiStop and the sticker said 26x 2.125 Wheel Master so not sure what it is and i'm using a Manic Mechanic adapter clamp.
Since i built the bike i've constantly had problems with the back wheel going out of true. and then about a month ago i had 2 spokes break their heads at the hub.then i got another one break a couple of days ago. someone mentioned that the adapter might be loose but i've already checked that and it's on there as tight as i would dare try,it aint touching the spokes.
of course it would seem to me that the spokes are breaking because their not properly tensioned but that brings back the question, why do the spokes keep coming loose?
So if anyone could give me some pointers as to what i could be doing wrong or what might be bad..
Also anyone that posts would you mind telling what kind of wheel setup is and if you have problems with spokes. Thanks
Oh..im running a 4stroke husheng with the ezqmatic trans. not a 2stroke

biknut said:

Torque the hub adapter to the hub @ 20-25 ft lb. Hub adapters don't cause spokes to break, or rims to go out of true.

Single wall alloy wheels with 14g spokes can't handle the demands a motor bicycle puts on them for very long. You can expect a wheel of that type to go out of true, and have broken spokes quickly, unless you ride very conservatively. A wheel with 12g spokes can have the same problems depending on,

How much do you weigh? How fast do you ride? Does your bike have any suspension?

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The Rim I have looks like its just single walled..its just bent over inside where the tire bead sits unlike the old s7 rim i had that looked like it was hollow inside ..Meaning it was Double walled?? I weigh about 210 and normally riding around 25-29mph. and no it dosn't have any suspension
I have a 58T sprocket

biknut said:

Doesn't sound too unusual. Your bike probably weights at least 60 lbs. That's double what a normal bicycle weighs. You're riding 30 mph. That's double the speed a normal bicycle goes. You weigh a hefty amount for high speed riding without suspension.

You'll need the best rims, and spokes possible to get reasonable life from a rear bicycle wheel. Hunt for a double wall rim with 12g spokes. The wider the better. Expect to pay $150 or more. In the mean time keep your speed below 20 mph on bumpy streets, and you probably won't have problems.

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is there any coaster wheel that you would suggest with a hub compatible with the manic mechanic adapter? 1.520-1.528"
I've never got anything but the cheap stuff because id never had any real problems with them. so now that i'm getting up the price line not sure which ones are good and whichn ones arn't so worth it.

does custommotoredbicycles.com have anything that you would recommend?
thanks for your help

I just got in from looking at my wheel and i noticed that on the coaster brake side of the wheel the spoke flange on the hub is bent,so when you spin the wheel it has a wobble from side to side.
I can definitely see it moving side to side when the wheel is spinning, but on stopping the wheel and examining it closely i cant see any bend in it which sounds ridiculous now that im writing it.

would that most likely have been cause from the adapter being loose at some time or something else. and how much would that add to the problem of spokes breaking?