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Discussion Starter #1
Initial symptom is that the starter motor turns and engine does not. Haynes says: sprag clutch. So I pulled that tonight and inspected. Haynes says if it is:

a. locked up
or
b. spins in both directions

It is bad. Curiously it spins in one direction and locks in the other. I even put it back on the crankshaft and tested extensively. It has the grip to spin the crankshaft in one direction and slips easily in the other.

So I hook up the battery and thumb the starter. The starter motor turns and turns the starter gear on the crankshaft ... IN THE DIRECTION WHICH THE SPRAG CLUTCH SLIPS.

So I have narrowed it down to two possibilities:

1. sprag (one way clutch) is installed backwards.

2. starter is getting the wrong polarity of juice and is spinning backwards...thus spinning the starter gear backwards...thus slipping the sprag...thus not turning the crankshaft.

So my questions are:

1. Is scenario #1 possible? I have not dismanted the sprag yet, but it appears it can only be installed in one direction.

2. Is scenario #2 possible? Will the starter spin in reverse if given the wrong polarity of current?

Thanks all.

-Trent
 

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I've seen a starter spin in the wrong direction. For some odd reason the "memory" of the starter changed and it did EXACTLY what you are describing. It would spin the starter, and the engine would stay still. This was a 97 GSXR 750 motor. The way I fixed it, was to disassemble the starter and pull the stator out of the starter (thereby removing it from the magnet, and "clearing the memory"), then reassembling the starter and giving it a short with the right polarity to "reset the memory". I know this sounds odd, that a starter could change it's rotation for some reason, and then be re-taught which way it should rotate...but it worked. Try it and give us feedback.

Good luck.

Ps. I believe the reason for the starter changing rotation, was that it had been sitting unused for an extended period of time.
 

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The starter clutch (sprag) is supposed to grab in one direction and freewheel in the other. This is normal.

Here's my two cents.......I think the clutch is supposed to be unlocked when spun in the same direction as the starter motor.

Thinking out loud..........looking at the engine from the left side (the side you'd see the starter gear from), the crankshaft spins counter-clockwise (CCW) so the starter should also spin CCW (it's a three gear system).

While the starter is cranking the engine, it transmits torque (CCW) thru the intermediate gear (CW) and then to the crankshaft (CCW) thru the starter clutch..........for it to do this the clutch has to be locked.........so the clutch needs to lock in the clockwise (CW) direction (opposite to the rotation of the crankshaft).

Once the engine starts, the clutch has to unlock so the engine doesn't constantly spin the starter, so it unlocks in the CCW direction (engine RPM overtakes starter RPM).

If my reasoning is sound, the starter should spin in the same direction that the clutch unlocks. In other words, turning the cranckshaft CCW shouldn't turn the starter. The clutch should be unlocked.

Weird? Sounds like it at first. Think about it in terms of what is transmitting the torque when cranking the engine vs. once the engine has started.

Now the question of why does the starter spin but the engine does not?

Has the engine been apart? The clutch might be installed backwards. From the crappy line drawings in the parts catalog, it looks like the clutch can be installed backwards.

If the engine hasn't been apart and the starter motor spins in the correct direction the clutch or it's mating parts might be worn/bad.
 

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paulo57509 said:
The starter clutch (sprag) is supposed to grab in one direction and freewheel in the other. This is normal.

Here's my two cents.......I think the clutch is supposed to be unlocked when spun in the same direction as the starter motor.

Thinking out loud..........looking at the engine from the left side (the side you'd see the starter gear from), the crankshaft spins counter-clockwise (CCW) so the starter should also spin CCW (it's a three gear system).

While the starter is cranking the engine, it transmits torque (CCW) thru the intermediate gear (CW) and then to the crankshaft (CCW) thru the starter clutch..........for it to do this the clutch has to be locked.........so the clutch needs to lock in the clockwise (CW) direction (opposite to the rotation of the crankshaft).

Once the engine starts, the clutch has to unlock so the engine doesn't constantly spin the starter, so it unlocks in the CCW direction (engine RPM overtakes starter RPM).

If my reasoning is sound, the starter should spin in the same direction that the clutch unlocks. In other words, turning the cranckshaft CCW shouldn't turn the starter. The clutch should be unlocked.

Weird? Sounds like it at first. Think about it in terms of what is transmitting the torque when cranking the engine vs. once the engine has started.

Now the question of why does the starter spin but the engine does not?

Has the engine been apart? The clutch might be installed backwards. From the crappy line drawings in the parts catalog, it looks like the clutch can be installed backwards.

If the engine hasn't been apart and the starter motor spins in the correct direction the clutch or it's mating parts might be worn/bad.
What he said +1

Curiosly, me and my brother got this when we installed a light flywheel on his 996S. We installed the sprag the wrong way around, so it didn´t lock/grab, but free-wheeled when trying to use the starter. So the sprag CAN be mounted wrong way around.

//amullo
 

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I've put the sprag in backwards too!

...and if you put it together with grease as an assembly lube (just use engine oil) it WILL fail... At $157, education doesn't come cheap...

But if I save someone else the expense it will all be worth it! :)
 

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Discussion Starter #6
Sprag was actually installed backwards. It took me a while to figure it out based on the Haynes pictures, but once I got it all apart and started reassembling it, it became very clear. Now I just need some case sealant, a new crankcase bolt and washer, and a few days of sunshine!

Thanks all,
Trent
 

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Glad you got it figured out. Good job.
 

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Discussion Starter #8
I'm glad it was that and not that crazy sh*t you were talking about! I've never taken a starter apart before so I was kind of hoping that wasn't it. On the other hand, I figured it was, because I didn't put the motor together, but I was the one that wired it up, so I figured more than likely it was my mistake! Thanks again all.

-Trent

bubbazenetty said:
Glad you got it figured out. Good job.
 
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