Craftsman DYT4000

[AdamH90]

Hello all,

Ok, so I am at a compete loss. I received a Craftsman DYT 4000 from my grandfather that had been sitting for since about 2011. The mower when I first got it would not start and he assumed it had been a short. Upon further investigation with my multi-meter I found a bad relay, replaced and the real problems began. It began with a hard to start and assumed it was the stater. I began tapping on the starter with a screwdriver thinking it may work like a car stater and needed a bit of a little jolt. After a bit I decided to replace it, hard start persisted but considering the age I decided to leave the new on anyway. I then checked the valves and push rods, which were straight, and reset the valves to 4000th of an inch. replaced everything, hard to start persisted. I began feeling the flywheel and found that when spun the hard spot made a squeaking noise and figured it might just be some gunked oil so I placed some sea-foam. Hand turned the engine to make sure it got into it and the next day went to try again but to no avail. To make sure the oil was actually moving in I opened the oil spout and turned the engine to make sure I heard bubbling and got splashed with the oil and got a wonderful wiff of gas. upon draining the oil I found it was chock full of gas so I inspected the carburetor, which was jammed open so I went ahead and just rebuilt it as well. I put it all back together put new oil and replaced the oil filter it now spins over great. New problem, no combustion, checked my magneto and it has a resistance of 4k ohms, new spark plug and tested it to my brothers mower and sparked perfectly, but no sparks on mine, I have cleaned the magneto and flywheel, but nothing. I was going to try my brothers magneto to mine, but unluckily doesn't fit so no way to test without buying a new one. It seems like it would be hard for a magneto to go bad so I am at a loss before buying it. Any ideas as to what this might be before I go paying for more parts? Pictures to come.

Motor model is Briggs and Stratton: 31P7770348E1

Thanks

 

[AdamH90]

Here are the pictures of the mower itself along with model numbers for the engine and mower.

 

[bertsmobile1]

:welcome:

The magneto grounds out via that thin wire to stop it sparking so you might like to test the engine with the kill wire dsconnected.
Secondly there is a Hall effect trigger built into the coil so a resistance reading is meaningless.
The carb throttle butterfly should be wide open when the engine is not running and held in that position by the govenor rod and arm.
Modern fuel is electrically conductive at cylinder pressure so a new plug is in order.
I use a red neon ( Ok orange ) in line spark tester in my mobile kit so I can see if it is sparking at cranking speed under cylinder pressure.

Old engine that have not been run for a while can be a real bitch.
You oft get some corrosin which makes the valves hang till it has run for a while and polished the corrosion off.

Get some starting fluid and give it a short shot down the plug hole then crank it over and see if it fires.
If you get a bang then try again squirting down the carb.
If you can keep it running with short shots of starter just before the engine slows down to cranking speeds then your problm is fuel related.
If you get no joy from the starter flid and there is a spark pull the top cover and flywheel nut/bolt , check the ignition key is should be dead square.

 

[mechanic mark]

https://www.briggsandstratton.com/n...nginemanuals.html?searchrequested=31p777-0348 Clean engine with shop vac. See page 5 for armature air gap & valve adjustment specs., operators manual.