i have removed the timing cover on my 1969 Commando to replace the crankshaft seal. After getting the cover off, I see that the chain appears to have a lot of slack and the damper is about worn out. I have had the harmonic damper redone by the Damper Doctor as it had slipped. I have a couple of questions: - Does anyone know a number for a neoprene lip seal for the crankshaft instead of the packing that was originally used? - Are there any opinions on using a double roller chain/sprockets vs. the OEM style? If the double roller type is used, are dampers still used?