Jetting is not about the porting completely.
Re jetting is about air coming into the engine and exhaust going out,and the fuel it will need.
The 1978's have the so called Key hole carbs. They have an accelerator pump system.
If you have a stock intake and stock exhaust all you may need is one step up on the main jet and adjust the mixture screw .
Try that first.
Depending on how it accelerates it may need a shim or two under the slide needle. MID range. 1/4-3/4 throttle. Each shim is about .022 thousandths.
Little brass washers you can get at the hardware store.
That is because the midrange could be lean.
Make sure that you sand the washer flat first. They have a burr on them from being punched out.
Also make sure the accelerator pump nozzles all work when you have the engine OFF and you advance the throttle, you should see fuel squirt out of all four nozzles. Make sure the float bowls are full (fuel petcock) ON. If that does not work it will be way too lean. Probably be hard to start too.
If everything is working right and you have the air mixture screws out TWO-2-1/2 turns (the max) and it still hesitates or back fires when trying to advance the throttle, then you will have to order new idle jets #42's from Sirius Consolidated in Canada.
But someone on this forum may have that same year bike and same modification and if they are not too lazy they will chime in and help you .
One change at a time ONLY.
