That sounds like a slipping clutch or auto transmission. In either case you need some work.
If it has no display for gears, and you don't count them in your head, you can only tell it by the speed you are going and the amount of revs, but only if you are quite experienced. Which gear you are in is quite irrelevant however. What matters is that your revs aren't to high or to low for the speed that you are traveling or for the power that you require.
To increase the speed of the engine, which is measured in 'revolutions per minute' - shortened to RPM or 'revs'.
it basically lets the bike work at higher revs, for example on mine it gives it unlimited revs, so it wont stop at about 6000rpm like a normal bike but just keep going, it can be bad because if the revs get too high the engine may explode
generally , two strokes are smaller capacity , shorter stroke, higher revs. for given engine capacity , long stroke /small bore = high torque / low revs short stroke/big bore = low torque / high revs
Rpms, revolutions per minute.
The powertrain control module will start cutting back on the fuel if the engine revs are going too high
cid
Sounds like transmission trouble. May be transmission is not upshifting into high gear
Possibly a stuck or sticking EGR valve.
I'm not sure what you mean by "Hard" but if it's reving high adjust your idiling screw.
Pro: you are able to change gear when your engine revs are different from your transmission revs. Con: when torque is high or the difference in revs (see above) is too big, it will slip.
The vehicle speed sensor is a common failiure of this symptom. It is located on the gear box, often just un-plugging it will cure the problem