Regarding the question - replace parts? rebuild? What's the difference? Both operations involve replacing parts like the needle, seat, jet, metering needle, gaskets and possibly the float. Rebuilding goes the step further to replace the throttle plate pivot shaft and bushings. Years ago, without changing the bushings (which require some special tools) you could order the pivot shaft and that would correct half the play in the throttle shaft area. It wasn't a perfect fix but went very far in getting an SU to behave. The last time I visited Joe Curto he explained that the throttle shafts no longer come pre-drilled for the pins which hold various linkage bits. That has to be done on a jig made for the purpose. SO - rebuild or replace parts? If you have play in the throttle shafts bring the SU to a specialist. If there's no play and you have the ability to follow instructions you can replace the easily replaceable parts yourself. - Dave