Can You Reverse A Starter Motor's Polarity?

I am building a starter for my kid's racing Kart using a 12V automotive starter. The problem lies in the fact that the starter turns the wrong way. I reversed the polarity- positive to ground, and ground to positive, and it turned the way I need it to go. Can the starter operate by reversing the polarity? I only need it to turn over a 5HP Briggs & Stratton.

 

Any DC motor will spin the opposite way if the polarity is reversed. However, whether or not you can do this in practice depends on how it is wired. You need to separate what is currently the negative from the case. That may not be possible.

 

re wire the cart for positive ground. that oughta do it, but i dont know if the gear will engage(if your using a gear), its designed to engage turning a certain direction...(right?)

 

Like Bort62 says, it will spin either direction...but will it kick out the bendix?

 

I don't know what direction you need to go. On my sons Jr. Dragster we used an early ford 6v starter. hooked it up to 12 volts. It spun the direction we needed, which was opposite of most other starters we were looking at the time. The self kicking jack-shaft mounted on the end made sure it disengaged after the engine started.Don't ask the direction, it was 7 years ago

 

I friend of mine has the old Ford 6V starter that you speak of. It turns the correct way because I believe it mounted on the car facing backwards. I didn't want to use that style because it weighs sooo much. I am using a Ford PMGR (permanent magnet gear reduction) starter. There is no bendix as it spins the crank directly.

 

just a thought....my 55 pontiac has the starter mounted on the drivers side of the engine, so does it turn the opposite way v.s. a typical sbc starter which is mounted on the p***enger side of the engine ?
or am i thinking totally wrong ?? the starter is about the same size and weight as a sbc starter.

and yes on a typical sbc starter the bendix gear will only kick out when turned a certain way. (damned if i know the direction a starter turns...lol) if the starter turns backwards, the gear will not kick out.

 

What about a marine starter....

 

good thought...don't marine engines turn the opposite way ? meaning, big block /small block chevy for marine applications.

 

yea i had a truck with a off shore 454 in it i dont know how thay built the damn thing turbo 400 np205 4x4 im still a little shocked ?????? but the starter was on the driver side

 

Putting the starter on the opposite side of the engine will not change the rotation of it. However, if you put the body of the starter behind the flywheel, as opposed to in front of it, the starter motor itself now has to spin the opposite way to turn the drive gear the same way.

 

It doesn't matter which side of the engine the starter is bolted on (left or right), it still turns the same (wrong) way.

 

what kind of engine are you working with?Briggs or something like that?

 

Exactly, just turn it around.

 

ok...that would be a big "duhhhh" on my part...i'll be quiet now.
i knew something about what i typed didn't sound right....lol

 

Well, yes and no.... as in yes you can and no, it won't do you any good.

Most starters are a universal motor, meaning the magnets inside are actually electromagnets that are energized by the current from the battery. Reversing the input polarity will reverse the electromagnets as well as the armature, resulting in the motor spinning the same direction with either polarity applied.

Universal motors can be run on AC or DC, offer a high power to weight, a wide range of speed and are very rugged, which is why you'll find them on everything from vacuum cleaners to dremel tools to automotive starters.

You could open up the case and move some connections around to get where you want to go.

Any permanent magnet motor will spin the opposite direction with reverse polarity. David

 

I did reverse the polarity, and it did go the opposite direction.( the right direction I need) I was just wondering if it would continue to work with the polarity reversed.

 

We used to race 5HP Briggs. Get a starter off of a 292 Y-block ford, Just weld a 12 point socket on the end of the drive and it will work fine as it will freewheel when the briggs engine starts. Put a push ****on tractor type solenoid on and fab up a set of handles that mount to the flanges to hold onto while starting.

 

What kind of starter is it?

 

Ford PMGR, (permanent magnet gear reduction) off a 5.0 Mustang.

 

What I oughta do is maybe read all the replys written by the poster...

"Ford PMGR, (permanent magnet gear reduction) off a 5.0 Mustang."

It'll work great, no issues at all, so long as the bendix or whatever kicks it in and out works for you.

 

Update:

I needed a remote starter to fire off my kid's 5HP Briggs powered racing kart, but I did not want to shell out $400.00 for one, so I built it myself. A little rummaging through the junk pile turned up a late model Ford PMGR starter from a V-6 Mustang. I cut off the un-needed starter snout, and tossed the solenoid. An aluminum bushing was pressed into the starter's end, and machined for a 12MM sealed bearing to support the end of the armature. An aluminum box, a motorcycle battery, a remote Ford starter solenoid and a starter ****on finish if off. The end of the starter shaft spins a 1/2" socket extension and a 3/4" socket spins the bolt on the end of the crankshaft. It worked great, but spun the wrong direction. I reversed the polarity, and now it turns clockwise like it should. I have less than $100.00 in it

 

Bendix probably won't kick out with reversed polarity. Try one from a motorcycle.

 

Your good because of the permenant magnet field coils. It's reversable because of that. and a lot lighter than an old style motor.

An old fashioned wired field motor would need internal changes to work.

Like was mentioned, just weld a socket on the end, and a push ****on to engage a solenoid/relay and go racing.

Frank

 

You could use an old Delco starter and rewire the field coils to have them reversed from normal. The bendix drive will be the problem child as it free willies the direction you need it to turn. Have you checked into a starter from motorcycle and see if you can jury rig it? Small, but will turn over that "powerful" B&S you have. Or you can go to Harbie Freight and buy a 9HP with electric start motor. It will also have a way of charging your battree and run your cart's lights and other stuff, like a boom box.

 

Only SOME marine starters are reverse rotation.usually when used in a dual engine craft one engine will rotate b***-ackwards to off set torque steer, but not always. {I had an uncle who ran a boatworks back in the day.}

 

Check post #22. I reversed the polarity(positive to negative and vice versa), and it works fine. There is no bendix, so that was not a problem. There are some pics of the completed starter device.

 

Several decades ago i was working on a semi truck that had a detroit diesel 6 71 engine . We changed the starter and it started up and ran backwards. Seems they made left and right hand rotation versions of this engine and the left hand starter had the field coils wound in the oppsite direction. Took me a while to figure that one out. OldWolf

 

If anyone else out there is looking to do this check out a late 80's Mazda RX7 starter. They mount on the back of the bellhousing and should spin "backwards" with normal hookups.

 

It's a DC motor guys, so it will run backwards with reversed polarity, and there should be no problems. He also said that it doesn't have a bendix, but is direct drive to the crank.

A little side note: A lot of DC motors are optimized to run one direction, and are built based on the RPM the motor is designed for. DC motors have "timing" believe it or not. The timing is related to the position of the permanent magnets to the armature, and of the brushes to the commutator. Ideally, you want the magnetic flux in the armature to peak right when the poles of the armature are in the midst of the strongest part of the permanent magnet's flux field. So there is a little "advance" built into this timing, since it does take a short time for the flux to build in the armature. Now if you take this same motor and reverse the polarity, it will run backwards, but it will not produce the torque nor the speed that it does when running in the "proper" direction.