Own measurements, not factory data. All done after the engine was well warmed up and rpm are stable. The cold engines provided up to 10% more thrust.
26cc:
16 lbs on tuned pipe and Menz-S 18x8 @ 7600 rpm
35cc:
20 lbs on tuned pipe and Menz-S 18x10 @ 7600 rpm
18.5 lbs on muffler 3271 and Mejzlik 18x10 @ 7600 rpm
21 lbs on tuned pipe and Mejzlik 18x10 @ 8100 rpm
58cc:
40 lbs on KS tuned pipe, Menz-S 24x12 @ 6100 rpm
37 lbs on KS tuned pipe, Menz-S 22x10 @ 7300 rpm

edit: My scales are accurate within 1 oz at 55 lbs

You are welcome to add your own data on the engines you have. Please state muffler, prop size/brand, and rpm along with the thrust measured