At times the starter solenoid will click rapidly either due to its failure or battery and/ or ground terminals that need attention. Also possibly a starter gear issue. If you set the park brake, you should be able to turn the key while checking it out under the hood to determine were the noise is coming from.

thanks, tomplum. battery (new) and terminals are OK after test,,,will check on starter gear...

So, how did you test the terminals?
Did you load test the battery? New ones are bad far more frequently than one would expect.

Battery installed with correct polarity?

thanks, bill kapaun. the battery registered 12V plus on the test meter, headlights were bright...tried to restart couple times and everytime i get that rattling noise (sounds more like a burst of machine gun fire) but that is it...the motor wont crank nor start.

Post the Sears 917.xxxxxx number-
The YS4500's I have schematics for only have headlights with the engine running.

12V on a test meter is meaningless. 8 penlight batteries will generate 12V, but certainly not produce enough amperage to crank an engine!

"Chattering" can be a sign of several different symptoms-
LOW/BAD battery is the MOST COMMON!
Battery has enough power to "pick" the solenoid.
Starter motor engages which immediately drops the battery voltage so low, the solenoid (and thus starter motor) disengages.
Battery voltage jumps back up, allowing the solenoid to re-engage..
Repeat.....

Until the battery is LOAD TESTED, you are peeing in the wind.

i got you bill kapaun...will get a new battery (and just return it if needed) hope this works.

Apparently, you have a DYS4500.
That has a different electrical system IF the head lights work with the engine not running.
A YS4500 has a separate lighting circuit off the alternator which requires the engine to be running.

I did request you post the Sears 917.xxxxxx number in my opening reply!

You can probably do a simple battery test IF so-
With the head lights ON, crank the engine-
Do they dim, go out completely or???

Your battery may simply need to be charged, unless it was working. IF it was working, you may have a charging issue with the tractor and the battery simply ran down.

More specific details would be useful.

haven't got new battery yet...meantime i hooked the test meter leads to the battery cables...it now reads 8V...turned on ignition and it snapped back to 5V...chattering now is weaker than before...still would not crank the engine...hope this info might help?...also is it safe to jumpstart it with my car battery?

here's more detail, bill kapaun...engine is kohler 26V twin,,,the lights dimmed when i turned on the key...willl look into sears 917 post...thank you.

A fully charged battery reads 12.6 Volts.
At 12.2 V, it's considered too low to test and needs to be charged.
Hint-

bill kapaun...after reading post 917 i decided to jumpstart using my car battery...mower motor started on first try...let it run for a while w/o the jumper cables, turned it off, and tried to restart...it won't...so now i know the mower battery is bad... i bought a new one with 300amp...mower started on first try...i cut grass for say 20 minutes then this happened:could not get out of an uneven ground surface so i turned the engine off and pushed the mower to even ground and tried to start...it won't...i tried more than a couple of times...everytime the motor cranks very strongly but won't start...what is it this time?...i checked the gas and got plenty...help...appreciate your patience.

Until you POST the SEARS 917.xxxxxx number OFF the tractor...........I have no idea WHAT model this is of the over 1000 various Craftsman tractors.
YS4500 doesn't do it!

finally, the motor ran on first try today...i guess there was not enough gas somewhere in the system and letting it cool down overnight did the trick...Thank You ... i would not have come down to this without your inputs, mr. bill kapaun...thanks to Garden Web too.