Hey Gerryg,
I just had made the Modification with the Roller Bearing. It works well, so far. The Roller Bearing could be a little bit higher. The OEM-Roller sports this Dimensions: Outer Dia.: 16mm, inner Dia. 8mm, Hight: 7mm. So it is neccessary to shim the Roller earing out, that it is located on Centerline. Or even a Roller Bearing with Hight of 7mm. But those are hard to find.
After Reinstall the Carbs and Syncronizing them, I found the Effect that it was difficult to get a sadisfying result for the Idle setting.
Reason was:
OLD Throttle Shaft Sealings. A kind of radial Shaft Sealing in "V"-Shape. Thereby the open V shows to the Outside of the Carb. I had contacting Hitachi Astemo (sub. Org. Aftermarket in Germany) for Spares. Awaiting an Answer of them, soon.
Link: for America :
https://www.hitachiastemo.com/en/groups/americas/ try to find out which of the listes addresses is responsible for Aftermarket Business (e.G. for Spareparts).
regards
Anja