Actually an FM radio may not fix the issue. FM will glitch just not as readily as AM.
More than likely what you are experencing is loose metal to metal connectin somewhere. Check all of the screws that screw into metal and tighten/loc-tite them as needed.
Also check the antenna wire attached to the rx to be sure it is not cracked, skined or loose. Many things can cause your symptoms and it's mostly trial and error to fix. Some other things to check are the crystals, the clutch bell, the exhaust and anywhere there is metal touching metal.