1985 cr 250 top end rebuild

Me and my friend are rebuilding his top end and basically finished. We tried putting the cycllynder back on which the top end rests in. However on the front left bolt (if loking at bike from the front) there is a plastic peice, that is a lever. I think its called the crank shaft reed (not quite sure the name). Anyways the plastic peice obstructs the cyclinder from dropiing in flush. The manual said to set the plastic peice in the foward postition which we did, but the cylynder still wont drop into the bolts flush. Do we have to somehow take out the plastic peice to install it? Or are we just freaking idiots and cant figure out why? If anyone has had this issue in the past please reply. This stupid plastic peice is preventing me from riding!

Thanks for the responses guys.;... OK yeah ill get a pic up as soon as possible. I took off off my right side of my crankcase in my top end rebuild too on my yz. but my friend (who think he knows more about this than me even though he has never done a top end rebuild) Doesnt think that is where u can get from it. I cann see where he is coming from because its hard imagine that peice coming into that box. It is on the front inside of the bolt (if lookin from back of bike). I told him to try it but he is afraid of ripping that gasket, even thugh i told him to replace tha gasket with the rest. Nrxt couple days Ill post a pic. Thanks for the help