I concur with the regulator issue. The LM317 is older technology and consunes at least 10 mA doing nothing. I haven't the foggiest idea why people tend to put the larger cap on the output of the regulator. Not necessarily a good idea.
12V is generally more common for things like a sealed lead acid battery. Put a small cap, like a 0.1 uf ceramic cap across the motor at the motor.
i can obtain the 6v parts i already have a 6v 4 ah battery, but can get a very powerful 12v battery. so just a small cap across the motor nothing across the battery?
No. You need some decoupling, regardless of the battery voltage. I would still recommend:-
(1) Add a 10uF electrolytic cap from the regulator pin 1 to ground.
(2) Add at least a 100uF electrolytic cap and a 100nF metallised polyester cap in parallel with it between the circuit +V and ground connections, close to the battery.
(3) The picaxe should have a 100nF decoupling cap wired between its Vdd and Vss pins, as close to the chip as possible.
Ah, KISS's post crossed with mine. He mentions the LM317 current consumption. You might find a low power version of the 7805 voltage regulator would be better (it wouldn't require the 2 resistors to set its output voltage). You only need a few mA at 5V for the picaxe etc.
You don't need a 'very powerful' 12V battery unless you're intending to mince your chickens! A bunch of NimH AA cells should be enough as the motor will only run occasionally.
12V 4.8AH is ok, even if a lot more than strictly necessary.
A 7805 has internal components which set the voltage. It has just an input pin (+12V in your case), an output pin (+5V) and a ground pin. It would have, say, 100uF from the input to ground and 100nF from the output to ground.
I thought you were going to use a much less powerful motor; but that's an option. If you do use a wiper motor you would need to reconsider the choice of fets to switch it. Check what Chrisatronics uses.
That's often the way with designs....they evolve as different contributors think of improvements, or workarounds for problems which come to light. It's what makes electronics an interesting hobby!