650 ss head found with intake sleeves

Norton  Engineers thought the motor would perform  well without the sleeves. In comparison tests they found more "drivabilty " with the sleeves and smaller carbs (monoblocks). Better midrange.

Hello the propose of these sleeves was to stop the twin carbs from freezing up and to atomized the fuel mixture Better witch they found in testing produced 3 more bhp So the option is yours they will not do any harm if you leave them were they are. Yours Anna J

always give better response at anything up to 3/4 throttle or so. They also tend to make starting easier.

Of course if you want the last 5% bigger carbs are needed but how many of us honestly have the throttle fully open for any length of time?

hello  you can now buy  new sleeves from RGM motors  So now you can have  new ones witch will be better for carbration  ,  yours  anna j