Originally Posted by disston
I don't think the part about "early" carbs having the one hole is a good way to say this. I have a 1975 R90/6, which is earlier, and it has 4 holes.
Good point I should have said some
Perhaps it was only flat tops that were deficient in enricher holes.
So Bing knew how to engineer a progressive enricher in 75. I can't fathom why they went backwards in sophistication bewtween 75 and 79 and then needed a service bulletin to put it right.