As the ASP and Magnums are the same engine, that carb has a bit of a quirk on the mix control and if your engine isn't setup correctly, it can be a rough running engine.

Check the manual for inital carb settings. Note that the mix control doesn't screw into a stop, but out to one. If you get the hIgh speed to rich and the mix to lean, it is not a good running engine. I about took a hammer to my Mag 70 when I first got it.

Set your carb to inital settings then after warming up the enigne, peak the high speed jet then go back rich by 500 RPM. Now set the throttle as slow as you can get it and keep the engine running. At this point, lean the mix control for maximum RPM.

Go back and do the high speed and then the mix again.

IF the transisition isn't good, tweek the mix control 1/16 turn at a time until it jumps to the throttle. My Mag 70 will bark like a gasser. If the enging dies when you jam the trottle from idle, the mix control is to lean. If it stumbles and slowly gains RPM, the mix control is to rich. Adjust acordingly.

By the way, the four strokes have little change in rpm over the last 1/4 throttle opening. I usually put some expo on the throttle to make the sitck more linear to the rpm changes.

Don