What brand is it? I find that most new-manufacture Stanley spokeshaves are utter crap, especially the convex sole models. I had the same problem and figured out that the issue was that Stanley appears to make the convex sole model by simply taking the flat sole model and milling the sole convex. The castings in old spokeshaves took the shape of the sole into account, so you could have a narrow throat.
This results in a huge throat, which is why you get the tearout. If you make a sketch, you can visualize what happens when you remove material from the sole like that.
As far as usage, when you use a spokeshave, you should be bearing down on the sole ahead of the blade.
Since I tossed my Stanleys in the junk bucket, I'm a happy camper with my Lee Valley/Veritas 'shaves and my vintage 'shaves.
If you're determined to make your shave work, there's a good article a few years back in Fine Woodworking on remodelling new 'shaves to get the desired narrow throat and make it usable. The process involves raising the the bed with thickened epoxy to narrow the throat and provide a uniform bed so the blade will be less likely to chatter.
Also, new 'shaves have crappy cap irons / chip breakers. The edge is rounded because they're tumbled to polish them. This makes them tend to clog with shavings, since the round edge allows the shavings to jam under it. The article recommends making a new cap iron out of 1/4 ins brass as to make the old cap iron work would involve removing too much metal to get to a sharp edge.
Or, you could get an old 'shave and revivify it or buy a good one from Lee Valley, Lie-Nielsen, or Dave's Shaves. Myself, I tend towards buying new, 'cause I'd like manufacturers of quality tools to continue to exist.
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