If you have a voltmeter it's an easy question. If not, Harbor Freight sells a slick little unit for $5.
Put the leads across the case (scratch off the paint for a good connection) of the starter and the power input stud, not wiring terminal, the 3/8" or whatever copper stud coming up out of the starter.
Hit the button, hold it and read the volts. If 10v or less for a 12v system, or 5v or less for a 6v system, your problem is not your starter necessarily (see later) it's a sulphated up battery that can't put out high current, or it's partially discharged. You can test for that by putting your voltmeter leads across the actual battery lead studs and measure while cranking. If you don't have 11/5.5v the battery is the cause.
If that's not the problem it's wiring. Either your cables are bad or the connections are dirty, not on the outside where you can see necessarily, inside where metal touches metal where the current flows.
Fine we got through that.....all clean and bright and tight.
Now we notice that the ground wire connects to the engine block via a steel screw on one side of the machine and the hot lead connects to the starter solenoid terminal. Fine.
First of all steel is not all that great of an electrical conductor. So you need a lot of surface area for good conductivity.
The path for the ground connection current to flow is from the steel bolt, through the cast iron engine block, over to the interface of the starter to the case of the starter and wala we have completed the path and the starter can spin.
But wait. What about the connection between the starter case and the engine block? Steel to steel, butt joint, hasn't been off or cleaned in 20 years sort of thing. The steel bolts have long ago developed a rusty scale.
Easy to see if this is the problem also. Just put your voltmeter on the WIRING TERMINAL that is under the steel bolt where ground is established to the block, and the other scratched into the starter case like you did initially. If you read anything in the way of voltage, you need to clean up that path.
On to the starting solenoid. This is your high current switch that you activate by the low current circuit associated with your starter push button, or key twist to start position. Inside are 2 hugh copper studs and a large copper disc that is sucked down to contact the studs (completing the circuit) when the button is pushed.
Over time due to the circuit parameters, the contact arcs and causes pitting, just like ignition points. Any pitting reduces the surface area of the contact. To pass high current you need lots of that. So if the solenoid is your problem, you will be able to read voltage across the two large terminals while spinning the starter. Time for another.
Once you have addressed all this easy stuff and it doesn't solve the problem, then you can do something with your starter. Sometimes it just means cleaning up the armature and a new set of brushes. Sometimes you need to include a new set of armature bushings with that. If it's worn beyond that time to bite the bullet and get a new one.
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Today's Featured Article - Hydraulics - Cylinder Anatomy - by Curtis von Fange. Let’s make one more addition to our series on hydraulics. I’ve noticed a few questions in the comment section that could pertain to hydraulic cylinders so I thought we could take a short look at this real workhorse of the circuit. Cylinders are the reason for the hydraulic circuit. They take the fluid power delivered from the pump and magically change it into mechanical power. There are many types of cylinders that one might run across on a farm scenario. Each one could take a chapter in
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