Your more than likely overloading your mower grass to high, mower to low or the blades are dull.
this happens when i'm not cutting, mower is just sitting there idling up and down
Most governors are supposed to run the mower as fast as safe for the mower but once it reaches that speed will slow it back down.
It sounds like the spring that helps smooth this out may have broken and let it go out of control, if you see where the spring goes you could go to a mower repair shop and get one and replace it yourself or just take it to them shouldn't cost much.
the spring is still attached and in good shape, but thanx for the advice
Then just cut the grass and don't worry about it, sounds like it ok to me.
the idle at its high end is not enough rpm's to mow the lawn, thats why i would like it to idle higher and smoother, also....without the varying rpm. Thanx.