This is completely normal. When you remove the glow plug you take out the compression the engine has. When you tighten it up you get the compression back. A tight compression is a good thing! The older your engine gets the more wear it will get as well, resulting in a loss of compression and power. If the pull start it too hard to pull just loosen up the glow plug a few turns and start the engine from there, then tighten it back down quickly. Make sure to let the engine warm up before running it though! And go easy on the gas when it is warming up.