Well, here we have on offer here at my web site are Brand New main jets for your CB750 HONDA.
These are 140 JETS and come as a set of FOUR (4).
Ready to use and easy to fit. I offer sizes in .5 increments through out the parts pages of this site, so look at the size you may need and simply purchase.
Many people buy from me as they either want stock size jets, or if you are like me and want to get more performance and have added pod filters and an exhaust, you will need to increase your main jet to allow for the hop up you have done to your bike.
If you are not sure, locate the stamped number on the carb rack, this will tell me what main jet is stock for you and can decide if you need a bigger size for your application. I have used maybe 50 sets of these and never an issue, these are brass and the same I have used for many many years.