I changed the front sprocket from 15 to 14 teeth and here is my thought.
2021 390 adventure with aluminium top box and side cases;
220lbs man often riding 2up.
70% city riding and 30% motorway riding (50-75mph, usually 60mph cruising)
First of all, Gas Mileage is not affected, if you are bothered by 1mpg difference, go get a 125cc scooter.
Stock gearing is OK, dont change if you dont want.
Here is just my opinion.
Q: why changing from 15 to 14?
A: stock 1st gear is too tall and I feel the clutch is over stressed at stop and go traffic.
Q: is 14 teeth solve the problem?
A: kind of, 14 provides 7.1% lower gearing/torque. it is noticeable at start up but the RPM at highway is increased significantly. (the mpg is not affected much, not noticeable.)
Q: pros of 14-45 setup?
A: 1.better startups. 2. a lot fun when riding wide open throttle and in moutain area. 3. can changed to 6th gear at speed of 45mph (a usually speed of chinese expressway, 15 45 is terrible at 45 mph because 5th is too low and jerky and 6th gear is too tall and engine runs rough below 4000rpm)
Q: cons of 14-45 setup?
A: 1.too much gear changing,25 mph at 4th gear intead of 3th, 40mph at 6th gear.
Q: RPM difference?
A: THE SPREAD SHEET IS BASED ON MY PERSONAL BIKE DATA AND THE SPEED IS NOT GPS SPEED. (1 MILE DIFFERENCE)!
Q: if 14-45 is too much of upgrade, what about 15-46/ 15-47?
A: 15-46 is not noticeable of change.
Highway tourer, 90% highway riding:
1.one person with luggage, stock ratio.
2.2up with luggage,15/47
2.2up racer? 1290 R instead
Mixed rider， 50-50 city and highway
1.one person with luggage, stock ratio or 15/47.
2.2up with luggage, 15/47 or 14/45.
City rider， 90-10 city and highway
1.one person with luggage, stock ratio or 15/47 or 14/45.
2.2up with luggage, 14/45 or 14/46.
Q: 14-49 setup?
A: U R Nuts. I believe if the bike is geared too low, you will feel when you twist the throttle, the engine waste all the energy reving up instead of pulling the bike forward.