Won't start with muffler on...

Hey all,
I've been doing some searching and haven't found this problem yet. I haven't ridden my 58cc Starfire in a while, and was getting back into riding gas bikes again. It previously had about a year of daily riding.

I cleaned out the carb, inspected the head and piston, made sure the tank was rust/debris free, new line/filter, fresh plug and fresh mix.

Thing is, it only pops over with the muffler OFF.

When the muffler is on, it does nothing; the wheel turns with the normal engaged resistance, and I come to a smooth and exhausted halt. It doesn't sound like the engine is doing anything at all.

It won't stay going while the muffler is off, but it will at least turn over and pop a few times.

Fully clogged muffler? (It's a black cat)

Yeah dude, seriously...wth?

Anyway, I didn't even consider dirt dinners/bugs. I tried blowing through it with all my lungs had- no joy at all. It's a catalytic converter, which I collect means it's even easier to clog. I soaked it in carb cleaner for ten minutes, rinsed and repeated, also to little effect.

I'll try the solvents first as suggested, and move on to the charcoal grill if that doesn't work.
Thank y'all for the replies

Well, except for sub.66;
The grown ups didn't think it was funny, son.

Dirt dobbers. Not dirt dinners.
I haven't considered those since I was a kid.