Ns125f rebuild basketcase running rough

[Kit352]

So I picked up a rough ns125f and have been slowly rebuilding mostly due to difficulty finding parts and information. I've got it up and running on the road but it runs really rough. I had the engine redone with a .30 bore so that should be all good. I suspect it my carb causing the issues but I cant seem to straighten it out. It is a bigger than standard one but it's what came on the bike and I found that it was an upgrade at the time. It's a phbh28 instead of the oem 26. It's also running a pod filter and micron pipe.
Bike starts and idles fine. Has a bad flat spot at 5k to about 6500 then again at about 8k and will rarely rev past that. Take of is a little boggy as well. I've tried upjetting it a size and that just made it worse and the plug black. I cant remember the exact setting at the moment but it was the recommended setting for that carb and combo I got from some forum. It's also the same jetting the bike had when I got it. Mixture screw is turned out 1 full turn.
I would swap to an oem carb if i could find a clean one. They all seem to be pretty poor on Ebay.
Where should i start to narrow this down? Compression is fine and it has a new coil. I've looked for alains tips but the link is dead. Anyone got a copy they can send me?

[MarJay]

Carb? Back to standard.
Airbox? Back to standard.

Then try. You'll never get it running right on a 28mm when it's supposed to have a 26mm, and what the pod filter is doing is anyones guess. The fact that it runs at all is a bonus in my opinion.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

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Pod filters and bigger carbs are very difficult to get the jetting right on a 2T. Honda made the original airbox and carb to be spot on for over 20bhp, why change them? A later GP bike wouldn't have pod filters, they still had airboxes, albeit some were pressurised.

If the pipe is definitely a Micron built for the NS125F, put the rest back to standard and up the main jets by 20 or so to start with.
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[Kit352]

Thanks guys. I have been able to source a ratty but functional airbox that looks complete on Ebay but not the carb. A few more popped up recently on Ebay that I'm going to bid on.

[Kit352]

Well i was able to fit the ebay airbox onto the bike with only minor troubles. The mouth of the carb was just a little bigger than oem so i had to use a thin coating of grease to slip it into the airbox duct. It runs much better overall but is certainly slower. The pod filter had big power hits while the aibox smoothes everything out. It got rid of the nasty 5k bog and pulls to redline now so i am happier anyway. Im sure it needs carb tuning now. Feels like it really holding back until 8k rpms.

[Easy-X]

Now you're starting to get to a reasonable benchmark: change one thing, see how it is "nope, it was better before" rinse and repeat
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