first of all, whens the last time it was started?
if its old, fuel may have become gummed up inside the engine which requires a rebuild.

second of all, did you check all the basics? (fuel, battery life in starter, glow plug life?) there is a ton of things to check before you go messing with the needles. if the guy ran it before he sold it to you, odds are its tuned enough to get it started.

if i were you i would take it to a hobby shop and have them get it started to began with. they will know the ins and out of what needs to be checked to get it started with out frying your engine (if it isnt fried already).