Once a battery is a couple years old, it becomes suspect if starting problems occur. Get the battery tested. Just getting 12V with a voltmeter (VM) is meaningless. You can do that with 8 penlight batteries, but they wouldn't start your tractor. IF you have headlights, do they dim when it "clicks"?
You CAN do other test with a VM however.
IF you have a VM, start by measuring battery V WHEN cranking (at the POSTS). IF V drops to near 0, the battery is bad/discharged. If the V stays high, you have a bad connection somewhere in the circuit.
Let me know if you have a VM, and I'll relate the rest of the procedure.

Don't have a voltmeter. The battery is new, however, as of yesterday.

I tested the starter by itself (i.e., cables straight from the battery), and it appears to be functioning properly. Perhaps I need new wiring?

The starting relay is bad. Your key closes a low amp circuit, which pulls in a relay. The relay, in turn, closes a set of high current rated contacts that connects the battery positive directly to the starter terminal.

When the relay goes bad, it does not close the contacts all the time. The "click" you hear is the relay trying to close.

A new battery can be bad, but it does sound like a bad relay/solenoid.

Ok, so how does one replace the starting relay?

Follow the positive cable from the battery. That cable should go to the start relay. Another cable will go from the start relay to the starter. One small wire will go from the keyswitch to a small terminal on the start relay. Depending upon how your tractor is wired, there may be a second small terminal with a wire that goes to a safety interlock switch.

You need the correct relay for this tractor. There is more than one type.

Well after you have replace a few hundred dollars worth of stuff, adjust the valves. Detailed instructions at wconner5 at verizon dot net

Walt Conner

Duh- as I slap my forehead!

Walt is probably right!
IF the exhaust valve has too much clearance, the compression release doesn't work. This can result in the same symptoms you describe.
Check/adjust the valve lash first!
IF the problem persists, we can go from there. IF SO, disconnect battery ground cable first.

Model# 917.20670 doesn't come up on Sears website.

"Model# 917.20670 doesn't come up on Sears website."
Yeah I noticed that myself. I'll double-check, but I seem to remember that happening before, last time I had a problem.

If I have to replace a few hundred dollars worth of stuff, then I'm booting this thing to the curb and just buying a push mower!!! My yard doesn't NEED a ride-mower (although I do enjoy it), but the previous owner had it and I talked him into leaving it behind for me.

I appreciate all your help thus far...I'll get in touch again soon, but there's not much else I can do with it today. Got family coming into town in a few days, gotta get other higher-priority things done.

I would think toward this being solenoid/electrical related based on your description. To much valve clearance will cause the engine to roll around fine until it hits the compression stroke at which time it stops. At that time it will click until the pressure bleeds down and then will roll around some more. Do check the valves to rule that out.

networker

If you want to rule out the valve issue, then just roll this tractor to where your car is. Put a set of booster cables on the car battery. Put the positive cable onto the terminal on the starter that has the heavy cable attached to it. Take the negative booster cable and press it firmly against the engine block or tractor chassis with the ignition key in the "ON" position.

If the engine spins over easily and starts, remove the negative cable from the engine block or tractor frame. Try this a few times. If you get the same results, then you just proved two things.

1. The valves are likely adjusted correctly

2. Your tractor has a seperate starting solenoid somewhere.

So let's pretend that the above scenario has occurred.

Next step.

Take the booster cable off of the starting mower. Trace the heavy wire that is on the starter motor back to the starter solenoid. Put the positive booster cable onto the OTHER big terminal on this solenoid. Clamp the negative booster cable lead to a clean spot on the engine block or the tractor frame so that it makes good electrical contact.

Now try starting the tractor with the keyswitch. If the clicking noise is still there, the a new solenoid should solve the problem. The clicking sound is the solenoid pulling in. However, the round disc inside the solenoid is not making proper electrical contact and needs to be replaced.

Well, do tell us what you find the problem to be. This same thing has played over and over with these B&S OHV engines on this and other lists so much I am amazed that isn't the very first thing checked. A hundred valve adjustments to every bad solenoid which is one of the things frequently replaced, after the battery, the starter, the battery cables, the ignition switch, on and on. Maybe not quite a hundred. (grin)

Walt Conner

The worst way to troubleshoot a problem is to start throwing parts at it.

You could buy a voltmeter for as cheap as $16.99 at Radio Shack, and that would have allowed you to troubleshoot all of the electricals. A voltmeter would have cost less than a starter and a battery and you could use it again and again. If you don't own a voltmeter (with a continuity tester), troubleshooting anything electrical becomes very much hit-or-miss. (an aside- I have 2 voltmeters, an analog and a digital one. The analog one comes in handy when I need to troubleshoot my points-and-condenser equipped car)

Follow castoff and walt's advice. Those things ought to set you straight.

"I tested the starter by itself (i.e., cables straight from the battery), and it appears to be functioning properly. Perhaps I need new wiring?"

Thinking about that, it probably is solenoid. That is if "functioning properly" means the engine turned over normally.

A valve adjustment probably wouldn't hurt anyway. Just consider it normal maintenance.

As an Long time mechanic I have found that the problem you are descibing is very often caused by a battery cable that has become corroded under the insulation. This will reduce the amount of amps the battery is able to supply to the starting system and other electrical components.
Although it could very well be the solenoid, I would ckeck the cables first.
Hope this helps!!
nomaddaddy

Does anyone have a link to site that gives the valve adjustment instructions? My Craftsman tractor has B&S 18HP Intec OHV engine, model no. 31H777. Thanks!