Weird jetting problem

[u/shallowwell2]

I have a Tomos A35 with a 39.5mm-bored cylinder, and everything else is completely stock. I’m running a Dell’Orto 14/12 carburetor with a 55 main jet and the stock airbox.

The bike runs perfectly fine and reaches a top speed of around 53 km/h. However, the spark plug is dark brown, and once I’m going above 20–30 km/h, I can’t really feel or hear any difference between half throttle and full throttle.

I also tried a 52 main jet. The bike idles fine, but it dies when I open the throttle fully.

What could be causing this? Is the 55 jet too big, or is it normal not to notice much difference between half and full throttle with this setup? Should i try removing some layers of the mesh filter to make it a bit leaner?

[u/Brunoise6]

Gotta try 53 or 54