Erratic engine cranking

i had a ignition switch that did that, caused erractic cranking.

OP could jump out the switch to see if it helps

By drag, do you mean that because the bearings are worn, the armature rubs against the stators?

A neighbor had a riding mower where the starter was at first acting erratically, then wouldn't start at all. It wasn't more than a few years old, he just uses is on a small lawn. I helped him diagnose it a bit. He had a new fully charged battery in it. I used a jumper cable to go right from the battery to the starter terminal, eliminating the solenoid, key circuit, etc. When I made the connection there was a reasonable amount of sparks, ie it was gettting current, but it would not move the engine. From that, I concluded the starter was bad. He bought a new one and it didn't fix it. He finally had Sears service come out and fix it. They told him it was the valve adjustment. Still leaves me mystefied. I know they use some kind of compression release during starting on some of these to make them easier to turn over. I guess maybe that was affected by the valve adjustment to the point that the starter couldn't generate enough torque to turn it over? IDK, but it may be food for thought for DaddiOH

That's what I'd... check the valve clearance. The exhaust is the compression release on most of them and it's critical for easy starts. Be sure you read how to do this and follow the directions or your apt to do more damage than good. For B&S

In the case with my neighbor where the starter would not move the engine even when directly connected to the battery, an apparenty it was a valve problem, I wish I would have thought of the very simple test of removing the spark plug and then trying to crank it. If it's a compression release issue, then with no plug it should spin easily. It also quickly rules out issues with the solenoid, start key circuit, safety circuits, etc.

I wonder, are they now downsizing the starters to save money so that without compression release, they can't effectively spin the engine? I mean back when I last had a garden tractor I don't think they had compression release for starting. In fact, I kind of thought that was reserved for hand start engines.

When I was doing a lot of generator service I ran into hard start problems caused when engines needed valve adjustments. The overhead valve engines were very easy to adjust the valves on but the older design in block valve engines weren't as easy to adjust. I could heat the head and jug on one of the older engines with a propane torch for a few minutes and it would crank right up. ^_^

TDD

Fat-Dumb and Happy"

Right.

Thanks. Cables all seem good. They do get warm, though, after a bit of attempting. With lots of attempting they get hot.

I'm thinking it is time to call the repair shop tomorrow, too many possibilities for me :(

That I could try. Thanks to you (and the others that suggested it)

Thanks to all of you for your input. I'll try cranking without the spark plug (there are two, need both be removed?) to see if compression is the problem.

If the compression is the problem, it is off to the repair shop with it tomorrow. Same thing if it appears to be *NOT* the compression...too many variable for me.

Agaun, thanks to all.

Let us know what you find out.

I wonder if the ground side of the circuit might be an issue?

Does the deadman circuit impact the starting circuit? (shuts the engine off when tractor is in drive and no one is sitting on seat or on many if mower deck is running and you select reverse).

How does it crank with the ignition disconnected?

I cleaned it. Ditto the battery connections when installing the new battery.

The damn thing has tons of things that keep things from happening but with the seat thing the starter itself is locked out. Not the problem here.

How do you know? If the seat y switch is intermittent, making poor contact, it could result in erratic cranking.