It's usually a sign of a weak mixture caused by a low fuel level in the carb.
Have you ever noticed that if you disconnect the fuel line from the carb and start the engine, as it used the fuel in the float bowl the revs increase and will rev quite high when you get down to the last dregs.
It's how engine work and is a clue as to why you have jetting software to get the mixture right for the weather conditions.
While it's not too harmful for a Max, it isn't something I'd recommend for a normal barrel.
The other reason it can rev is because there is an air leak between the carb and reedblock assembly.
Are the five screws on the reed block tight?
If you accidentally leave them loose, you would find the engine rfevving quite high when you started it, due to the air being drawn in and weakening the mixture.
Also check that the throttle cable is free and returns with a nice 'clack' when you pull the cable and release it from behind the pedal.
Don't try it by using the pedal as it gives a false reading.
The bend it the carb cover is a notorious place for the cable to run dry and start fraying, especially if the cable is tight like a piano wire when you fully depress the throttle pedal.
A small amount of slack ensures that the cable and nipple isn't strained.
Do you always blow the fuel up before you start the engine, so that the fuel bowl is full?
That's about it I think!
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Rotax revs?? by 'Katosan' (12 Feb 2010 @ 1:59)
