Ducati Monster Forum

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Bought one fr a 2000+ engine , don`t remember year or model, f my 900 -97.
It spins backwards. :o Engaging a gear, sprag engages correctly, chain spins backwards! Is this normal?
Sprag is correctly mounted, not much more could be reassembled wrong. Old starter works OK,  chain in gear spins forward., sprag is engaged.

Have I mounted something wrong? Or some other mistake?
Anyone w same experience?
Or shuld i just stop taking those pills ;),
a bit confused here. ???

Was it a rebuilt motor?

how the hell do you get it to spin the chain? is this an older bike that will start in gear?

The armature could of been wound up backwards. There are also some people who have said if you iinstalled the case backwards it will spin backwards, but i dont belive thats possible since the case only fits 1 way. ( there are 4 magnets inside the case)

If the old starter works okay, why do you need a new one?


edit: After thinking about the actual question, if your brushes are in the wrong holders, that would make the starter spin backwards, right?

Dunno if starter was rebuilt.

Just put in gear, press starter button - chain spinning. Was just checking a few secs as I got more & more puzzled...

Maybe, but they only fit one way.

Old has 130 000 km´s on it and is quite worn.

The polarity is reversed, I don't know how somone could accomplish this, so no ideas how to repair it.  If the bike is on a rear stand and the bike is in gear or there is clutch drag the chain will spin with the starter

I have a starter that was rebuilt & does the exact same thing. People whom I've spoken to who rebuild these things tell me that with these particular starters, it's imposible to spin it backwarbs, but.......................................
If you figure out how to reverse the polarity, let us (me) know.

It reallly is impossible to get it to spin backwards unless someone took it apart, and rewound the wires inside backwards. The 4 magnets on the case only fit 1 way, and the brushes are interchangeable. You can only put 1 wire on it. I would get it to a starter rebuild shop, or any electrical shop and ask them if they some wound the armature backwards.

The only other thing ive heard, again, is the shell for it. I've heard that if you put it on the wrong way (its 4 very large magnets on the wall, each one with an alternating polarity) it will spin the wrong the way. But I dont think its possible since it only fits  1 way. (atleast the one i was messing with did)

 ???

If the starter motor is turning backwards, the sprag shouldn't engage, right?

Ummmm...good point since it is a one way clutch.  Now things make even less sense.

The devil baby from NMC is in on this. Are you sure your not just going nuts? take the starter, connect the power to it, and ground it, does it spin clock wise or counter clockwise?

I'm 99% certain that this is possible. If you rotate the shell with the magnets 90deg relative to the brushes it _will_ spin backwards, and I'm pretty sure it is possible to reassemble it and fit it this way. I had an extended chat about it in a thread over on TOB where someone else had done just this, and I recall when re-assembling mine that I noticed it was possible to assemble it both ways and I tested it to make sure I had it spinning the right way (but they're vague 6 year old memories now, and I haven't taken one apart since the question came up).

big

That still begs the previously raised question though, how does the reverse spinning starter engage the sprag and turn the engine and chain backwards.   ???


(Unless the starter's turning correctly and the transmission's making the chain spin backwards b/c it's in reverse.   ;D  )

That seems logic. BUT,
also have dismounted sprag and flipped sprag a few times during my starting efforts.
Sprag in one direction - didn`t engage engine to turn, sprag flipped 180 degrees - engine turns and rear wheel turns
backwards when checked in gear a few secs.


Interesting! Unfortunately it is apart now so I cannot check how it was put together.
But I did take it apart when bought it to check starter so could be my mistake.
Usually I line up the two fine lines on the shell w the ones on the bottom piece, then the lid w brushes
only fits in one position to get the positive screw from battery in the right position.
Both ends of shell matched, ought to be correct, right?

What happends if you rotate shell 180 degrees wrong?
Split engine last year, sorry no reverse gear...  ;)

If my understanding is correct, it'll then turn the correct way again - the 4 magnets inside are oriented N S N S, so each 90 degree turn (relative to the brushes) changes the direction of rotation.

big

OK, ian.
If you´re correct, at the moment your 90 degree theory seems like the logical explanation.
Maybe I didn`t put it together like I usually do.... :-[
Gonna try to test this today.

MOT test tomorrow so no test.
Still wondering how the starter could be wrong assembled...

There are only 2 screws holding it, so really, there is only 2 directions it can close, from left to right, NS, or SN. However it only closes 1 way ( atleast i was never able to close it the wrong way, it just wouldnt fit).

I still have the starter I referenced before, I'll get busy with it & report back.

One possibility I can think of for reversed polarity is if the previous owner made larger brushes from a different unit fit and the wires were long enough to reach wrong locations. 

Standard brushes & plate.



No test but a little thinking:

Brushes & plate only fits one way together and plate can`t be flipped and only fits housing one way:
http://www.ducati.ms/gallery/files/9/4/9/0/lid_housing.jpg
Little squares also inside housing and on plate & lid.

Magnets are 90 degrees apart, looking from gearside the 3 screws has an almost 120 degree pattern:
http://www.ducati.ms/gallery/files/9/4/9/0/gear_side.jpg
That means: Mounting housing 90 degrees wrong, positive lead screw fr solenoid gets in funny position (if possible),
I-you would notice that immediately. That wasn´t the case here.

Thanks all f input so far, any more thoughts?

I can't remember...can the magnets be removed and reversed?  Goin' for longshots here :P

THey probably could be, i think they are attatched via glue.

I suppose it could be a starter from another bike, they're fairly generic.
That's a wild guess.

that would make a lot of sense actually. They are just generic Denso starters found on kawis as well.

Not so impossible. Anyone know what the text on the plate is?
My original is so old, worn and repainted.
I`ll check the backwards one.

Plate says:

270 4001 1A
128 000 - 6050
12
        DENSO


And it´s not the 999 etc one, does not look like this:

(http://i10.ebayimg.com/02/i/000/f7/87/5408_1.JPG)

Something`s wrong w collector, reversed wiring or damage, is another theory.