I have been mountain biking for almost a year now and riding twice a week. I recently gave up smoking (6 weeks now ) and now when I cycle uphill , I felt some burning on my chest when my HR goes to 145. My maximum HR shold be around 180. My legs are still strong but my chest have those burning feel.
I quit a little over a year ago, and went through a variety of "funny" feelings when riding afterward. I actually felt worse for about two months after I quit than before. The odd symptoms gradually went away, and I now have much more endurance than I did a year ago.
Still, quitting smoking causes some pretty profound changes to your body chemistry, particularly in the short term. Plus, if you smoked for any length of time prior to quitting (20+ years for me), your lungs suffered damage which you body is now trying to repair.
If that burning sensation continues, I would certainly recommend that you see a doc.
Well, I would, but I'm 51. After about 40, you start to get paranoid about stuff like that. Even if you are considerably younger, though, I'm not sure I'd let a burning in my chest with exertion go for too long without checking with a doc.