What grade of oil is in it ?
Is it leaking heavily leaving patchs on the ground
Is it smokey at all
Last time you topped it up did you put the full litre in did you dip it afterwards were was it on the mark on the dipstick
http://www.amazon.co.uk/gp/aw/d/B009NRTBMY?cache=42d8d10aa6f9a30024ccc09f2555912c& pi=SX200_QL40&qid=1412700208&sr=8-3#ref=mp_s_a_1_3