I recently bought a used 2000 blaster engine to replace a worn out 88' engine. I rebuilt the top end of the 00' and after the first start up the engine, it has had a lot of vibration. It doesn't look like the lower end has ever been rebuilt, so I'm not sure if the counter balance is positioned wrong or not. I'm trying to figure out why the engine runs but has excessive engine vibration. The vibration is so bad when the engine is revved up it begins to shake things loose on the bike. Thank you for any help you can provide me.