Unexplainable loss of mid range in a 125

[noobi]

What reasonable explanations are there for a sudden loss of mid range power.
it started last Sunday when the bike wouldn't run properly, it was either throttle wide open or idle. nothing in between. just burbling, i changed the plug, same problem. i checked for blocked jets, same problem, i dropped all the fuel and rinsed tank and carb with meths to disprove water, same problem
. cleaned air filter, same problem. replaced fuel with different fuel/oil mix. same problem

the only thing i can think of is reeds, but i cant check them because the reed block is bolted is with a bolt with no head
the pipe is cracked but its been like that for a while and the loss of mid range is new

I'm going to get the pipe welded and the muffler re packed.

the jetting was fine last summer.

[gasser]

Other people on the forum have had the same set of symptoms and the problem ended up being trash blocking one of the carb jets.