Nice paint job!!
Is there a screw to adjust the fuel to air ratio?
Seems to be running lean ... bigger jet needed since the flow is much less restrictive ?
One thing I found out with a homemade intake, is keeping the flanges flat.
I had a number of problems originally on my bike with my intake adapters I made.
Found out the weren't entirely flat against the carb. Even with the gaskets it didn't help, air was seeping in.
Check with a straight edge and file or sand down the high spots.
In this case every little thing helps.
Sounds great but, I'm a little confused; how is the filter attached to the intake?
Be aware that using that chassis means you will need to use a jackshaft as the engine sprocket will be on the left of the engine (next to the seat) & the axle sprocket cannot run inside the axle bearing...
With such small tyres, you can safely start at around 5:1...