cam chain idler sprocket

there is a large plastic idler sprocket that goes between my cylinders and case on my 900 with 1015 block. the chain seems pretty tight without it and it doesn't seem to do to much. can i do without it? thanks, ryan

is it the front sprocket or the tensioner sprocket?is your cam chain on the sprocket on crankshaft ,is cam chain tensioner installed?if tensioner is allready installed remove it till your cams and everything else is installed .you need both lower sprockets plus the upper sprocket.

there is only one lower sprocket. it rides directly above the crank. the front/rear/tensioner/upper sprockets are already installed and i tensioned it and it seems fine without the larger lower one.

You raise a good question... Not sure what would happen if the center cam chain roller were left out. I would definitely not want to find out. Take that block back off and reinstall it using new rubber pads to eliminate rattling and superglue them to the arm that holds the roller. Point them up when installing the block.