Why not just let hardware handle most all of this for you?
Code:
' include your hardware/config stuff here

Revs VAR BYTE ' holds up to 255 revolutions
ANSEL = 0     ' disable A/D so RA4 is digital
CMCON = 7     ' disable comparators
OPTION_REG = %00110001 ' RA4 = count input
' inc count every 4th falling edge with 1:4 prescale
' assigned to TMR0

Mainloop:
    TMR0 = 0      ' clear count before pause
    PAUSE 20      ' Adjust this to set how long it counts revolutions here  
    Revs = TMR0   ' TMR0 counts 1 rev for every 4 pulses
    LCDOUT $FE,1,"Revs: ",DEC Revs

    ' do other stuff here, then return to get more counts
    GOTO Mainloop
This will be a LOT faster than interrupting on every single pulse, and counting
in software. You should be able to give the wheel a pretty good spin without
missing anything.