So... I lost one of the two little rubber pieces that goes on the bottom of the cam chain roller into the crank case. I just put together the cylinder head with only one of those rubber pieces. Will this cause any problems?
i'm assuming that you are talking about a honda 350, so.......yes, it can cause problems. it can cause any number of maladies to your freshly built mill like: clogged oil channels, an unstable tensioner mechansim, the rubber/metal bit can get wedged into gears/crank parts. just to name a few. my advice, pull it apart and fish that sucker out, you can use a magnet on a stick.
you can leave it in. the gears will spit it to the bottom it if it gets caught up there but most likely its lying in the bottom of your cases in between 2 casting ribs. the real problem is that its the cush drive for your tensioner. you need to have it there. so if you dont have an extra, youll need to get it out anyway. use grease to hold them in place. i pulled apart my old street motor and found them lying inside. my race bike swallowed 2 of them. i got them back after i split the cases. sometimes they are impossible to get out unless you slit the cases. they can get caught up just about anyplace in there. i mean, its probably better to get them out, but if you dont or cant, i wouldnt worry too much. but you DO need them where they are supposed to go.
oh yeah, you can always use the turn it upside down and shake it out method, but that'll almost drive ya crazy. the nice thing about leaving them in there is being submerged in 200 degree oil keeps them soft for use later.