Hi Lance
Sorry for the delay in replying. Your original email to the factory went down to the workshop and was in the process of being answered.
Anyway, I will answer your queries here.
The engine you have is of a very old design (pre 2000) and the engine has changed significantly since it became an SP designation.
It is difficult for us to diagnose what the issue could be, however realistically the original RCV60 was prone to vibration. New engines have helical cut gears and are individually setup to reduce any vibration. They also come with a metal backplate which reduces any possible vibration as a result of the engine not being tightened to a test stand or firewall securely (previously the tortional vibration meant the screws could dig into the wood of the firewall and ultimately loosen the fit.)
The carburettors we used at that time were Irvine (Perry) carbs. If you are interested, please email me and we may be able to supply you one of these from stock.
Best regards
laurenne
email
[email protected] if you have any queries