"Runs like shit" covers a lot of posibilities. Before going to the trouble of adding a carb spacer why not locate the cause of the problem first. If it is running rich it could be due to a leaking float valve, an aftermarket fuel pump that's delivering too much pressure, leaking power valve, dirty air filter, sticking choke........
If it's running lean check for an obstructed fuel filter, inoperable power valve, failing fuel pump, dirt in the carb.......
A failing ignition coil can also cause the symoptoms you described. Good luck...Al English
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