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Thread: How to test stator?

  1. #1
    apriliaforum expert SLORider's Avatar
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    Unhappy How to test stator?

    Anyone know how to test the stator? Measure ohms/volts? I already asked this less specifically and didn't get an answer. New stators are $370 USD apparently. I will seek out a rewind before paying that price! But, I sure as heck want to know if it needs replacing first.

  2. #2
    apriliaforum expert SLORider's Avatar
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    Lightbulb Answer

    OK-- I'll have to answer my own question, then...

    I am told by a kindly mechanic that measuring all three stator phases should yield in each:

    45-75 VAC at half red-line
    18-28 VAC at idle

    This would be measured by unplugging the stator connector (left side of bike) and placing a volt meter across the three yellow wires in all three combinations at the connector (pins 1-2, 2-3, and 1-3).

    Resistance measurement across all three phases should be identical, and should be around 0.8 to 2 ohms.

    The stator is three phase design with delta (versus wye) windings. Because of the expense of a new stator, I am looking at rewinding done by these folks:
    http://www.customrewind.com/

    I found pictures of their work here.

  3. #3
    apriliaforum expert RXV_Poor's Avatar
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    I'm looking forward to your results.
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  4. #4
    apriliaforum expert cyborg's Avatar
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    Hey SLO, good info as always. Can the same guys back East, (Ricks) that do the good starter motor rewinds do the stator rewind? I know they did a damn good job on my starter motor, it's still holding up well after more starts than any of my OEM starter motors ever survived through.



  5. #5
    apriliaforum expert SLORider's Avatar
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    borg, I thought of Rick's right away also. I might check with them. Customrewind.com was a referral from Electrosport because they don't do custom jobs--only off the shelf. Although, I'm really wondering if this is a Honda stator...

  6. #6
    apriliaforum expert irie's Avatar
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    I assume you've had the cover off and had a look? Could be a bolt has backed out and is slowly destroying the stator.

  7. #7
    apriliaforum expert SLORider's Avatar
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    Hey, there's a pleasant thought! Good call. We'll find out very soon as it's not rideable at the moment anyway.

  8. #8
    apriliaforum expert irie's Avatar
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    Had one bike do that even though the bolts had been taken out, thread locked, and re-torqued. The mess was quite 'interesting'.

  9. #9
    apriliaforum expert SLORider's Avatar
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    Lightbulb Testing Your Stator

    So, here is how to test your stator:

    First, disconnect the stator connector on the left side of the bike. There are three wires. With an AC voltmeter, measure the voltage across each combination of the three wires (pins 1-2, 2-3, and 3-1). The bike should be running.

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    You should measure:

    18 to 28 VAC at idle
    45 to 75 VAC at half red-line

    Here are my obviously bad measurements:

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    You can also measure the resistance of each stator phase (the bike should be not running for this test). The resistance of each coil should be equal and between 0.8 and 2 ohms.

    Since I obviously have a stator problem, let's open the cover and have a look. I laid the bike on the right side to avoid dumping oil.

    Remove the flywheel cover to reveal the infamous flywheel bolts. No bolts loose or backing out--good! Loose bolts can damage a stator.

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    Okay, now flip over the flywheel cover and have a look. There it is in all its glory! Above it is the engine rpm sensor.

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    A 7 mm socket is required to remove the five bolts. One of the rpm sensor bolts also secures a wire hold-down bracket (seen above) that keeps the stator wires from moving.

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    If you can't tell from the photos above, this image should convince you that this stator is fried. You can see the epoxy that insulates the magnetic wire windings is blackened and delaminating from the wires. There are sections of exposed copper. This means the windings are shorting out between the winds, effectively reducing the number of winds in each coil and causing the weak output.

    Although these epoxy flakes are not abrasive I think I will do an oil and filter change. They may load up the oil filter.

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    Next step: New stator or rewind?

    There are thin plastic insulators on each one of the 18 poles on the stator to separate the wires from the steel core. Some of them look melted a bit and this one chipped off in my hand. I'm not sure if a rewinder would be able to replace these.

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    Still wondering if this is possibly a Honda stator...

  10. #10
    apriliaforum expert cyborg's Avatar
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    Whoa! Yeah I would say you're toasted there SLO! Ricks may be able to rebuild the plastic pieces or why not just buy a new Aprilia one, how much are they? A lot of parts for the RXV aren't too pricey but I do wonder what made your stator coils fry. Maybe a dead short somewhere? They usually burn up when they have too heavy of a load for too long. I don't think you were running anything extra on the bike normally right? Perhaps the battery itself has some shorted plates and pulling a big load? Maybe starting with car jumpers, but then I wouldn't think the DC would backfeed into the AC side of the charge circuit, just damage the battery.

  11. #11
    apriliaforum expert irie's Avatar
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    That stator looks horrible! At least it hasn't been lunched by a loose bolt so I guess that's a bonus ...

  12. #12
    apriliaforum expert SLORider's Avatar
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    Quote Originally Posted by cyborg View Post
    Ricks may be able to rebuild the plastic pieces or why not just buy a new Aprilia one, how much are they? A lot of parts for the RXV aren't too pricey but I do wonder what made your stator coils fry. Maybe a dead short somewhere? They usually burn up when they have too heavy of a load for too long. I don't think you were running anything extra on the bike normally right? Perhaps the battery itself has some shorted plates and pulling a big load? Maybe starting with car jumpers, but then I wouldn't think the DC would backfeed into the AC side of the charge circuit, just damage the battery.
    New stators are around $300. A rewind is $140, but I need to ask about the plastic insulators/bobbins. I think this is a result of all the starting problems I have had--killed the battery dead flat, which then required excess current for charging. KEEP YOUR BATTERY CHARGED! Use a Battery Tender!

    Jump starting wouldn't cause this. The regulator/rectifier will not allow current to back-feed into the AC side.

    What is interesting is that the two 30 A fuses on the starter relay are in-line with the charging system. Since these fuses weren't blown, it seems that this damage was caused with less than 30 A current flow.

  13. #13
    apriliaforum expert kimzx1000r's Avatar
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    professor slo,

    thanks for sharing most interesting find. I will be interested to see if it can be repaired or have to be replaced. Also possible causes. Thanks again.

  14. #14
    apriliaforum expert RXV_Poor's Avatar
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    Thumbs up

    Quote Originally Posted by kimzx1000r View Post
    professor slo,

    thanks for sharing most interesting find. I will be interested to see if it can be repaired or have to be replaced. Also possible causes. Thanks again.
    Thanks for sharing SLO.
    02 Aprilia RSV1000
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    06 KTM 525XC
    06 KTM 950 ADV S
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    AMA, BRC, D36, CORVA, IMBA, STM

    Disclaimer:

    I'm impulsive, hard headed and sometimes really stupid. Please do not take anything I say or do as a "correct thing" or a "fix" as it could be harmful to your wallet or person. Never argue with an idiot, no one can tell the difference.


    CAL550 for Prime Minister

    King of Dirt 2009

    Magoo is my Hero

  15. #15
    apriliaforum prov-nov
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    i have had Baja Designs rewind a stator for me before and did a good job. Might want to see waht they say. Just another options for you and alittle closer.

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