Don't waste your money on the pull start, the old rope and new metal wire pull starts all fail after several uses. The centrifugal clutch, on the other hand, is very reliable and worth every penny.
Pirate Cycles has c. clutch for $30.00, and $5.00 shipping and handling. It will come from bgf for some reason, but you'll save 10 or 12 bucks, I just did this last week.
I just tried to order some from Pirate Cycles and got this message:
The Centrifugal Clutch is not currently available. Please contact us for availability of this item.