Sounds like you may have a wee bit of switch bounce. Look on General Config page top right and set a value of 2000 for the Debounce Interval and see if that helps, if it does then reduce until you have issues again, then increase slightly.
Hood

Thanks, works fine now. It was set to 400 and the box below to 0. I entered 2000 and 1.
Now I will try to install a opto switch for a RPM read out, I may bee back.

I may bee back.

OK Arnie see you soon. 

Phil

I am back for more help. I have got an opto switch from a friend which I hope I can use, but I do not know how to connect. From the attached data I think pin 1 and 4 is grounded and pin 3 is the output getting 5v through a 10 000 ohm resistor, but where and how is pin 2 connected used? Any help will be appreciated.

Looks like pin 2 will be the supply to the LED.
Hood