Yes, it's for alignment.. I took off the head and then moved the flywheel, which pushed the piston up, and up came the sleeve with the little pin already out and layin beside the sleeve (when I noticed it).. It must of came out when the sleeve rose upwards.. Anyway, curiosity solved it for me. I just removed the sleeve and figured out that the pin actually does go in further, so once it was all back together, the pin is actually flush with the top of the sleeve, and fits in a little notch to keep the sleeve from spinning.. So now all appears to be a-ok!!I just hope the thing runs next time I hook up the glow igniter and pull the cord!! Wish me luck!!