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2019/07/23 14:53:10

HollerDweller

Electric starter turns counter clockwise, Recoil starter turns clockwise?

   This just seems strange to me. I recently purchased an older Dr Trimmer Mower powered by a B&S 6hp Quantum Diamond I/C. It is equipped with electric start. The machine has seen little use, but looks like it was sitting for a very long time. Perhaps most it's life. It appears in all original condition with nothing modified or tinkered with. I have a background in rebuilding starters and alternators, but never messed with small engine components. The starter was seized so I removed it and did a quick refurb. It didnt need any parts just a good cleaning of the corrosion build up. After I cleaned the internals, it looks and functions like new.

   Here is what is so bizarre to me. The starter turns the flywheel in the counter clockwise direction while the pull starter turns the flywheel in the clock wise direction. I need to rebuild the carb so I dont know if it actually starts in either direction. I just find it unusual because if you were to manually start the machine, the head will spin in one direction, while vise versa via the electric starter.

   I looked up the correct starter model and sure enough it is the correct one. As far as I can figure by the pictures and diagram the starter gear actuator spins clock wise which will turn the flywheel in the counter direction.
   I hooked up my cordless drill to the flywheel nut and spun it clockwise and gave it a shot of starting fluid to see if it would fire and it did. So I know the engine will run. But this was before I ever took notice of the starter setup.

   Here is a link to the correct diagram of the electrical system of my engine model. This include the breakdown of the starter and corresponding part numbers. Everything seems to jive.

   I was under the impression that a 4-stroke is not capable of running backwards. Or am I looking at all this backwards?

Thanks! I have enjoyed lurking this forum for some time now and finally have a question for which I cannot find an answer by searching.

8 comments Leave a comment

Roy

You are right, the motor won't run backwards but the gear shouldn't engage the flywheel. The only things that could cause that are reversed battery leads or incorrectly wired brushes. I have never seen that happen.

2019/07/23 19:46:21

HollerDweller

Yes this is odd. After studying the images of replacement starters, it looks like the helical fluting of the starter gear actuator is backwards. The wiring is correct with the negative brush lead grounded to the body of the field housing. I correctly labeled the negative wire coming out of the starter body. I am baffled.

2019/07/23 20:50:44

kshansen

Just an off the top of head guess. Is this a permanent magnet starter motor? Is it possible the magnet housing got installed upside-down? for some reason I'm not seeing the link to the mage you say you posted.

2019/07/24 09:33:47

kshansen

Roy
You are right, the motor won't run backwards but the gear shouldn't engage the flywheel. The only things that could cause that are reversed battery leads or incorrectly wired brushes. I have never seen that happen.

Just reread this one, agree that a mistake hooking up battery could cause the problem but gear should not engage unless somehow it got the wrong starter gear for the application. Might explain why an older machine has had little use! Not impossible for a mistake to have been made at the factory, rare I'm sure, but not imposible.

I spent 40+ years working on heavy equipment and on a large Cat loader found a problem in a fuel priming pump one time that was the pump was wired up wrong internally and was running backwards! That was a small permanent magnet motor about the size of the one you are working on.

2019/07/24 09:45:54

AVB

It would a lot easier if the OP had posted the Briggs model and type numbers. That way we can look up which starter is being used. There were some two wire starters used on the smaller engines and it possible cross the wires up in the connector housing.

The starter motor clutch assembly does turn CCW to drive the flywheel CW so if the motor was turning the wrong direction and driving the flywheel then the wrong starter is on the engine as the clutch assy shouldn't be driving the flywheel.

2019/07/24 09:55:18

kshansen

AVB
It would a lot easier if the OP had posted the Briggs model and type numbers. That way we can look up which starter is being used.

Agree 110% we run into this very same problem over on the Heavy Equipment Forum I spend much time one. Too many people don't understand that any machine may have numerous variations from year to year or due to some option a buyer requested when ordering a piece of equipment.

Does not matter if it is a 6 horse Briggs on a lawn mower or some huge Cat bulldozer! And unlike most cars knowing the year of a machine is nowhere as important than the numbers on the tag!

2019/07/24 10:04:10

HollerDweller

Sorry about the link issue. I did not realize at the time I am not authorized to provide links. Here is the number on the side of the motor 12J707-1716A1xxxxxxxx. I could only find diagrams for the "A2" model but everything looks the same.

It is a permanent magnet housing. It is also keyed and had a recess on one side for the brush assembly. So it is impossible to reassemble the housing backwards.

I double checked yesterday and it definitely turns the flywheel counter clockwise. The starter shaft is supposed to rotate in a counter clockwise direction. With the gear reduction housing, it would spin the starter gear in a clockwise direction. I first thought I was just looking at it all wrong because of the way the helical shaft is. But it is completely opposite of what it should be.

As for the wiring, there is one wire that goes directly to one brush. It is completely shielded by a shroud inside the starter body. This is the positive lead. The other wire is exposed and goes to a chassis bond on the end cap which then goes to the opposing brush. This is the negative lead. If the wires were crossed, it would short out the entire electrical system and would result in some melted wires at the least.

Considering most of the blck paint was still on the starter gear and hardly any wear to note, this looks like a fluke starter was installed at the factory. That or someone tried fitting a starter for a completely different application. Who knows?

2019/07/24 12:03:29

AVB

Could very well be an oddball.

Try this if you have a cheap compass. On the one I on the I have here that turns correctly when the end is place over the compass the side with the leads the compass points South. If someone at the factory install the magnets wrong the compass will point North. Hope this make sense.

Alternately you could fashion compass using a floating sewing in water that been magnetize. The trick is getting the needle to float. I check the orientation several times using the floating needle here.

Also the helix when looking at starter with motor down climbs right to left to the top where the E-clip is.

2019/07/24 16:58:48

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Electric starter turns counter clockwise, Recoil starter turns clockwise?

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