This change will affect these models, 90-55, 75 and 100cc variable pumps. They added a rubber gripping element on the pin that goes in the main pump housing. It helps in retaining the pin in the housing while in normal pump assy. It also helps in servicing parts, maximizing the interference fit that is between the pin and the pilot hole in the pump housing.
The part number has changed to the newer pin model. And the pin is interchangeable with the older pin part number. But the older pin will no longer be available.
Older part number is 8100235. New part number is 8801135
If you need more info on this, call us at 800-361-0068 or send an email to sales@htsrepair.com