Go ahead and do the compression test, It will give a good lead on what might be wrong.
Make sure the fuel is off and both plugs are out and hold the throttle pinned open.
Hey 87shee, have you rode since you installed the impeller, If so any temp drops or any probems with it?
I need a pump for my shee I might just pick one of these up in stead of pro-design from FAST.
Your not going to get stuff like CP said at autozone, You can get some stuff real cheap at harbor freight don't know how well the stuff works from there.