Fresh oil coming out my exhaust

96 XR250R

People used to call me 'The fogger' because my bike smoked soooo bad. I tore it down and took the head, jug and pistion to our local 'rip you off because you dont have a Harley' bike shop; unfortuantly the only place in town the would do the valve seals and hone the cylinder on a motorcycle engine.

I got the head back and it didnt even look touched! but I still forked over the cash in hopes I was wrong. So I get the bike back together and it will only idle for a few seconds and when I hit the gas it died. So I rebuilt the carb. Now its runs, but I smoke 10x worse than before just sitting in the driveway and fresh, unburned oil was leaking out of the left exhaust port. I looked over the book I dont see anything I could have done to make this issue worse. I had someone come double check my vavle adjustment and its in spec.

Does it sound like I was ripped by the machine shop? Or is there anything else I should be checking?

The bike shop was supposed to change the valve seals. I put it all together with the factory Honda mannual and made sure everything matched the pic's. But I suppose I could have gotten the rings in wrong - first time I've ever worked on a bike. Thanks so much for the ideas, I'll be checking my rings soon (Im getting real good at pulling the head at least hahaha)

Would a big bore kit change the valves/seal size? The previous owner had a big bore kit done but I dont have any specs on it. I told the machine shop it had one but maybe that didnt get relayed to the tech.