I had a quick look online at a few jetting tables for the PHH carbs. seems their is a limited selection for idle jets. I would go for the 55 [seems to be the smallest ones listed] One noticable difference between Solex and Weber in regards to Idle jets is that the "Air bleed" hole is fixed in the body of the carb unlike Weber, where the "Air bleed" hole is part of the brass jet itself.




To save a few dollars maybe chase up another pair of 63.8's to match the existing pair you already have.