Coaster Brake Newb: Help?

Bought a cheap cruiser about a month or so ago, never worked with/ridden a coaster brake before, I got the chain tension taught and made sure the brake arm was tight in the clip/hanger mounted on the chainstay, just took her for a test ride and the brake applies when I put forward pressure on the pedals.

It's fine if I've got speed up and cruising, but if I stand up and pedal the brake comes on. All this and then the chain finally pops off altogether. Just to mention, it functions fine when backward pressure is applied too.

Is my chain too tight? Having said that, I popped it back on with a fair amount of slack > same problem.

Does it have a tension arm?

If it doesn't it should, if it does check for movement as the wheel could have moved.

Also check the chain isn't stretched. I ruined the stock chain on my beach cruiser by just not cruising lol

I'd suspect that pedalling forward doesn't actually apply the brake ( shouldn't be physically possible) but causes the bearings to bind up.

What brand hub is it? There'll be a servicing guide online somewhere, it's not as daunting as you might imagine.

it sounds like the wheel is on backwards?

Has a tensioning arm, all in place and bolted tight to its bracket, it's an unbranded hub so probably made of an old Aldi sardine tin.

Should the sprocket spin all the way round if you spun it with your hand? On my wheel, the sprocket moves so far forward > stops. And so far backwards > stops. All smooth and no grittyness, but is this normal at all?

Has a tensioning arm, all in place and bolted tight to its bracket, it's an unbranded hub so probably made of an old Aldi sardine tin.

Should the sprocket spin all the way round if you spun it with your hand? On my wheel, the sprocket moves so far forward > stops. And so far backwards > stops. All smooth and no grittyness, but is this normal at all?

They have a bit between braking and going which does nothing, it's hard to explain but with most it has some cone shaped bits inside that move along and either press against the outside of the hub to brake or lock into the center of the hub to go and then between is a gap.

While it is going it should feel just like a normal freewheel'd hub.

Thanks, yeah it was fine when in freewheeling mode. Mechanical trial and error is the answer, me thinks. Thanks guys.

Coaster hubs overheat pretty easily. Worth taking apart and re packing with plenty of grease.

5 minutes in the workstand, undid the tension arm and wheelnuts, reset chain tension and bam, works like a dream. Pretty likely I'd set the chain tension way too tight. Sigh.