Ive reinstalled and MIG welded stock suzuki
gears before, no problems but I also ordered new hotcams when my gear spun as it was a new issue to me then. While waiting for their arrival, I use an Oreilly auto parts pulley puller, took gear off, matched lobe hole to sprocket hole, pressed gear back on, then mig zapped the size of a skittle. Both cams, both sets. Years ago, many years, many hours with no issues.
Must be a fast zap as to not overheat
and warp the cam. But the weld is seriously no bigger than a skittle. No smaller than a tic tac. This hurts nothing. There are camshafts with fixed, bolted on, cam sprockets. If motor is timed correctly, the motor will work as its supposed to. This is a product of heat. Over and over again you heat the motor up. Heat expands metal, metal has "memory", If it was stretched out, itd remember it did that. Even if it cooled off and shrank, it still was overheated and stretched and knows it. Thousandths of millimeters are a big deal to press fits.
The guy on the kxf forum repressed and did not weld sprocket. He has his thought process on it. I have mine.
My opinion visually is its your intake side. This is the side with the tensioners pressure.
I dont know whats more work to you, pressing gears and welding or not, or buying new cams. Nows a chance to gain power with an aftermarket cam. Your choice. Of course a new cam chains a good idea too. Its a ten year old mx bike. They get hot and those cams are up top not at bottom bathing in oil...take plug out and rotate motor by crank by hand, hear if valves are hitting. Might never had. You could take head off and look. But I wouldnt reuse the gasket. And definitely use torque specs in reassembly. Or you could do a compression test to see if the pistons solid or a leak down test to see if a valve bent. My bet is your good. Itd would have stopped working. There are cameras small enough to fit in the spark plug hole. Another oreillys tool rental.
Youre not in bad shape. This happens to the best of us!