I would NOT IM or skin pop Ritalin. Pills are extremely dangerous to inject in any way, but IM and skin popping are sure fire ways to create a big ol abscess on yourself. Those pills have fillers that are disgusting and awful for you and will cause you a lot of pain if you IM or skin pop them. I would try to IV with that syringe before I IMed or skin popped it, but that's not a real great idea either.
If you're dead set on the needle for these, why don't you get some syringes from a pharmacy or needle exchange that are better suited to your needs? You should also micron filter these because Ritalin pills have talc in them. Over long periods of time, talc causes talcosis of the lung, which has emphysema like symptoms IIRC. Anything other than a micron filter will not filter the talc out and it will get into your body.