Clean all the battery, solenoid & starter motor connections.
This includes grounds, which includes such things as engine mounting bolts to the frame etc.

IF you have a voltmeter, see this link to isolate voltage drops the easy way.
http://www.excelauto.com/online/Tech.d/strvdt.html

Valve adjustment is the most common cause of the symptoms you described AT FIRST. I don't know what you are into now.

I have detail instructions for adjusting the valves IF you would like them, address below, put in proper format and remind me what you want.

Walt Conner

Well the address I forgot to include is -

wconner5 at frontier dot com

I forgot to mention about charging the battery and getting it tested-
Isn't senility cool!!!

All great advice above. Double check that the studs are secure in the block that retain the rockers while you are doing the deed. Something else that could be in the mix is to verify that the flywheel key now hasn't sheared.

I am going to clean all the connections this morning, voltage drop test is a good idea too. Thanks for the info.

Walt I just sent you an e-mail, thanks for the offer.

Battery is charged and testing good.

Thanks for all the responses, I appreciate it greatly.

Seems like everyone was right. I started by cleaning all electrical connections and that allowed the starter to turn well without the spark plug in, replaced plug, back to square one. Adjusted valves via Walt's instructions, starter spins fine with the spark plug in but still wont run. Pulled bolt in flywheel and the key was sheared. Replaced sheared key and it ran for about 30 seconds and sheared the key again. Thus far I'm guessing I don't have it torqued enough (didn't use torque wrench) and/or the washer that wasn't on it when I took it apart is needed to hold everything in place. What should the torque spec be? What is the washer part #? Am I anywhere near on the right track? Thanks for all the help thus far.

Sounds like you are on the right track.
The flywheel MUST be properly torqued to prevent shearing the key.
The key just lines things up, while the torque "locks" it in place.
I don't know the correct spec., but I'm sure one of the other guys can provide that.
Online search provides some different (suspect) results.

Download the IPL from the Briggs website to make sure you get the proper part#.
I think it's 690582

" Replaced sheared key and it ran for about 30 seconds and sheared the key again"

100 ft. lbs. torque, can't just guess at it.

Walt Conner

Found a washer off another engine and torqued to 65 ft lbs. Started and ran good for about 5 minutes, shut off and began gathering tools to put back together. Went to restart and it acted like it did from the start, starter laboring and wont turn it over. I hadn't properly torqued the valves so I thought they had loosened possibly. Pulled valve cover and adjusted properly to proper torque specs. Still seems compression locked. Had 2 others adjust and same scenario. I'm at a loss here. I get one thing right and the other seems to reappear.

You didn't specify which tractor, but if it's an LT-1000, you only have a 3amp battery charging system.

Figure the fuel solenoid takes 1/2 amp?? and it's not going to top off the battery in just a couple minutes.

"Found a washer off another engine and torqued to 65 ft lbs."

"100 ft. lbs. torque, can't just guess at it"

Walt Conner

Tractor is model 917270670, but I've been leaving the battery on charge when not trying to start. The 100 ft. lbs wasn't posted here when I made another attempt so I used your suggestion from another thread. I will go pull the bolt out, check the key and torque to 100 ft lbs. I will also make sure battery is fully charged.

Here is a link that might be useful: Thread where I read the 65 ft lbs

I removed the flywheel bolt checked key and torqued to 100 ft lbs. Battery has good charge, and voltage is getting to the starter. Re-adjusted the valves 5 more times. I'm either missing something on the adjustment or there is another problem.

The link you posted was for a different series engine.

Back to the voltage drop test to see where the "major" drop is.

There doesn't seem to be a "major" voltage drop, less than .2 VDC difference between voltage at the battery terminals and voltage at the starter terminal when turned to start.

Check voltage from big terminal on starter to starter case when cranking (like all the other tests).
IF you have a major drop there, the starter is bad.

You did adjust the valves with the piston 1/4" PAST TDC???

Shows 0.00 vdc between those two points. Yes, I've followed the directions as close as I can, including 1/4" past TDC. Seems like I'm missing something in the adjustment, but had other people follow the directions with the same results. Electrical tests all seem to be okay, valves seem to be adjusted, flywheel key is in tact and the everything is torqued properly. I've also done the test of watching the intake valve and it appears as though the compression relief is working yet still too much to start. I'm so baffled by the fact that it started once the flywheel was torqued and then would not restart. I appreciate all your time and effort with my mess. Thanks.

Briggs starters are pretty tough, but it wouldn't be the first one that died from a long period of getting urged to crank and engine that the compression release wasn't working. Two things to try. First, GOOD jumper cables from a known good battery direct to the starter. Make the last "connection" hitting the ground to the case of the starter. It will spark- so take no chances that you will ignite some fuel. If you are using the tractor battery, it's best to disconnect as to not arc the lug to death. Unsure the compression release is up to par? Slide a feeler gauge into the intake, set the brake and attempt to crank.

You might want to get the battery tested.
Maybe it was already on its last legs.

I have a 21 hp briggs v twin ohv that I just had apart.Can the alignment on the cam and crankshaft (two Dots) be 180 off?

No. What kind of issue do you have?

Swapped starters with another mower I have and still seems like too much compression. I'm unclear as to what sliding the feeler gauge into the intake and trying to start will accomplish? Willing to try just want to make sure I understand what your saying before I try and do so improperly. Battery is new and starts the other mower with no problem. Had an acquaintance suggest there may be 'carbon build up on the head causing high compression'. Not sure of the why or how much less how to fix said issue. Any other ideas? Thanks for all the help so far.

Sure. The compression release nudges the intake valve open enough to let some pressure out of the cylinder- making the engine easier to crank over. In slipping in the feeler gauge- your goal is to accomplish the same thing. Just to ensure the valve doesn't quite close. If the engine then cranks, that would indicate your suspicions on the compression release are correct. Every once in a while I get to do a cam on these, either for a worn lobe on c/r that is broken or has an issue.