FAILURE TO TURN OVER, Craftsman rider.

[mr-moe]

Engine is a B&S model 404577 0291E 031208
The challenge is when the engine is turning over to start, it turns as far as Top Dead Centre, then stops.
With the starter engaged, you can twist the fan to get it past TDC, and then it will continue to spin over and start.

Customer has installed a new B&S starter, and it checks out ok.
I have disassembled the engine thinking that there may be a problem with decompressor, as was the case with many of the singles.
The unit doesn't even have a decompressor.
I have adjusted the valves upon reassembly of the engine to slightly lower .004 clearance.

Battery is a 340 CCA and new.
I have replaced all battery cable connectors and soldered in place.
I have buffed up all chassis grounding points for negative cables.
Finally, I have run an extra cable directly from the - terminal of the battery to the engine block.

After 40 years fixing theses things---
What have I missed?
A little help is needed.

[KE4AVB]

Have you replaced the starter solenoid? They do develop high contact resistance which lead to a voltage drop problem.

[RoyM]

Have you load tested the battery? Are the connections clean and tight?

[bgsengine]

Don't forget - NOTHING beats an actual voltage drop measurement with your DMM - Besides what the prior 2 mentioned, also realize that just because you cleaned all the terminals and connections, that does not mean the wires themselves are not a problem, not to mention wires making good clean contact with terminals (corrosion inside terminals or wire insulation, broken wire strands, pinched wires, etc.) - Never assume everything is good just because you cleaned and looked at it - Take an actual measurement (voltage drop) between circuit points both on hot side and ground side while cranking.

[mr-moe]

All good thoughts, more checks required.
Stay tuned.
Thanks.

[Arkie]

Twin OHV Briggs engine.
Things to test:

pull both spark plug wires off so as to kill ignition and see if still hangs on compression.
(so as to check timing of spark as being too fast)

Block the air intake/carb throat and test crank. (this will reduce the compression when cranking) Check compression on each cylinder with intake valve lash at minimum. You can take valve lash to very minimum on each cylinder by just inserting a feeler gauge under each intake valve stem instead of adjusting rockers to zero lash.

I also use another battery and jumper cables straight to the starter terminal or to the solenoid cable going to the starter. (if voltage and current tests are ????'able Do not arc and ruin the starter stud threads when doing such.

Do not forget to check for hydrolock due to a carb float leaking into the intake. (test with both plugs removed then with only one/swapping cylinders during test.

Does the engine run ok if it starts????

I've felt your pain (cranking issues) and I'm a electrician and electronic tech with all kinds of electrical test equipment.

[rootuser]

Faced something like this recently with a Craftsman mower with a 42" deck, can't remember the number.

It ended up being the battery was acting very strange under load. It tested out fine on the bench. I cleaned all the terminals, checked the wire, the whole nine yards and it did the same thing. Would get to TDC and stop, although if I clicked enough times after (sometimes 5-6 times) I could get passed it most of the time.

I ended up hooking up the old Schumacher charger with the full 300 amp jump start and bingo, it worked. Totally stupid on my part for not checking that to begin with. Battery just had something wrong with it. Swapped it out under warranty and new one is fine. Issue resolved.

Sounds like your issue may be more complex.

Taking out the plugs and cranking with no compression and seeing what happens might be a good idea as mentioned already.

Back in the day building high performance stuff when a brand new engine would get stuck at TDC we would heat them up to get it to free and crank them a while when they were heated and that would normally free them up permanently but that was only on a fresh motor.

Lastly, the only other thing I have seen personally like this is when I had a motorcycle that would do this because the there was wear in the bottom end and there was some play and it would let the rod move just enough to let the piston get stuck at TDC. It was wasn't enough to damage anything yet, but did cause that issue.

I have heard, but not seen personally, needle bearings in the top end doing something similar right before they disintegrate. Hard to tell. All of this is on bigger motors. I just don't have the hours on small engines like this other than to hobby around.

Good luck to you!

[KE4AVB]

Just wait until get a battery that reverse polarity....It happened once to me about 35 yrs ago in my car. Parked one evening and next morning no start. Still don't how it happen overnight.