Okay, I've searched all over the internet for this and can't find the answer. Maybe you classic forum experts can help.

In the YS 60/61 series they went to a square machined head at one point and later to a cast square head. During this time (I think) the carb butterfly was changed from a rear offset to a front offset or vice-versa. Which offset is the newest?

I don't remember this offset change giving a significant performance change. Why was it done?

-Ron