Alternator question

I am working to put a ZTR back in service after sitting for some time. The guy purchased it at auction and soon realized he was in over his head. It is a Deines (Marty J). The original 18 horse Onan went south and someone swapped in a two cylinder flat head Briggs industrial 18 horse. They didn't finish the job. I have one of these mowers with a smaller deck and can't wait to use this one (it is the biggest they made at the time).

There is no regulator on it. There was an option of a 10, 13, or 16 amp alternator. Is there any way to tell externally which I have? deines mowers have shafts out both sides of the engine for driving the hydros and deck , so pulling the flywheel is rather involved. I was just hoping I could tell another way.

Also, would the pto shaft on the old Onan be the same size, etc as the Briggs (not tapered or anything)? They lost one of the pulleys. If they are the same I can just order a replacement from the factory even though I don't have the original engine.

You need the wiring diagrams for the engine and the mower, and a multitester. There may already be a regulator under the engine shroud. If you need to buy a regulator, buy one to match the biggest possible alternator. Regulators are generic and if you put smaller regulator with a bigger alternator, the regulator would have a short life.

Briggs and Onan made engines with different sized PTO shafts for various mower manufacturers. Unless you have the specs on both motors you need to measure the crankshaft on that Briggs. You'll also want to make sure the crankshaft is long enough to line up the belts when you put on that pulley, otherwise you may need to move the engine a little.

I would think the alternator amps could be found using the engine numbers.

Does this mower use a magnetic clutch PTO? Think it will need the larger alternator to keep up with the coil draw.

As for the missing pulley, at this point you'll need to do some measuring and engineering. Determine the shaft size, sheave diameter, and belt cross section. Probably have better success going to a bearing supply house with your information.

1. As far as the pto pulley goes, If you don't know the crank size of the Onan, Or its spec. number (so maybe you can look up the crank diameter), you are out of luck.

You said you had a similar but smaller mower, What size crank is in it? Does it have the correct size pulley for this mower?

2. Briggs is 'funny'about their charging systems. A lot of their older parts diagrams have all the charging parts on there, the mechanic has to determine which system he has.

The way to tell is the color of the wire(s) and the color of the plug from the stator under the flywheel. With that information, a good Briggs parts guy should be able to tell you what system is on your engine and what regulator you need to work with it.

But first, I would check for output from the stator. If it is 2 wires, should be something over 20v AC. between the 2 wires when running at full throttle.

If you have only 1 wire if might be the unregulated 12v, or if the wires are red and white, 1 wire is DC. and the other is AC., for lights. (You can't just take the diode out of the DC wire and make it into an AC stator, I tried that.)

Another thing: The desired size of the charging system determines what size magnets are in the flywleel. The larger charging systems have larger and sometimes more magnets in the flywheel on Briggs engines.