Can I measure across the stator wires for an OHM reading? I've done this on my Morini to get a feel for the integrity of the windings. Wondering what to look for ohm wise on a healthy stator.
Thanks,
Toby
Testing Stator Coils
Moderator: ajleone
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DewCatTea-Bob
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- Location: Near SE side of Lake Michigan
Re: Testing Stator Coils
[quote= tobydmv ....
" Can I measure across the stator wires for an OHM reading? "
____ Yes, however your ohm-meter needs a 1-ohm or less full-scale to get an accurate enough read-out.
" Wondering what to look for ohm wise on a healthy stator. "
____ That much depends on which alt.stator-model you have !?
What Duke-model is your stator from ?
Got any pictures of it ?
Duke-Cheers,
-Bob
" Can I measure across the stator wires for an OHM reading? "
____ Yes, however your ohm-meter needs a 1-ohm or less full-scale to get an accurate enough read-out.
" Wondering what to look for ohm wise on a healthy stator. "
____ That much depends on which alt.stator-model you have !?
What Duke-model is your stator from ?
Got any pictures of it ?
Duke-Cheers,
-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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ducwiz
- Posts: 604
- Joined: Tue May 22, 2012 12:52 pm
- Location: near Frankfurt, Germany
Re: Testing Stator Coils
Hi,
most of our ubiquitous digital multimeters ("DMM", mostly made in China) do not offer measuring in the sub-Ohms range. But they resolve voltages quite precisely. So, a solution to our problem can be: get a precision current source of 1 Amp., feed it with your motorcycle's 6 or 12Volt battery, then connect it's output to the low resistance device to be measured, and finally read the resulting voltage drop across the device - in our case the alternator winding. The DMM will displays the resistance value in Volt (or milliVolt), according to Ohm's law V = I*R !
In this document a cheap DIY solution for the current source is described: http://media.wix.com/ugd/3cf8ac_bd4c28c10a1644b59821a0039d137707.pdf
It is made from very few standard components. For 1 Amp. we need a (nonstandard) 1.25 Ohms resistor, which can be composed by connecting three standard 5.1Ohms and one 4.7Ohms R's in parallel. Unfortunately, the document is in German language. Maybe, JimF can have a look over it and give an explanation in english. Or ask me, I will translate/explain on request.
cheers Hans
most of our ubiquitous digital multimeters ("DMM", mostly made in China) do not offer measuring in the sub-Ohms range. But they resolve voltages quite precisely. So, a solution to our problem can be: get a precision current source of 1 Amp., feed it with your motorcycle's 6 or 12Volt battery, then connect it's output to the low resistance device to be measured, and finally read the resulting voltage drop across the device - in our case the alternator winding. The DMM will displays the resistance value in Volt (or milliVolt), according to Ohm's law V = I*R !
In this document a cheap DIY solution for the current source is described: http://media.wix.com/ugd/3cf8ac_bd4c28c10a1644b59821a0039d137707.pdf
It is made from very few standard components. For 1 Amp. we need a (nonstandard) 1.25 Ohms resistor, which can be composed by connecting three standard 5.1Ohms and one 4.7Ohms R's in parallel. Unfortunately, the document is in German language. Maybe, JimF can have a look over it and give an explanation in english. Or ask me, I will translate/explain on request.
cheers Hans
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tobydmv
- Posts: 88
- Joined: Wed Apr 16, 2014 4:59 am
Re: Testing Stator Coils
Bob, I have a 3 wire stator here on the scrambler. Looks like 2 yellow wires and one red. Reads something like 2.2 across the red and yellow. The monza is 2 wire, black and red and has a similar reading.
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DewCatTea-Bob
- Posts: 2897
- Joined: Sun Nov 01, 2009 10:53 am
- Location: Near SE side of Lake Michigan
Re: Testing Stator Coils
____ Sorry, it's been so long that I've forgotten to keep an eye out for any response-reply in this thread,, and for the past few days, I haven't been keeping close attention to the main topic-page to see if there's been any recent interesting thread action.
[quote= tobydmv ... " I have a 3 wire stator here on the scrambler. "
____ Indeed, as all 'Scrambler' models were produced with 3-wire alt.stator-cables !
" Looks like 2 yellow wires and one red. "
____ Since you've found two yellow and no white-wire, then your Scrambler-model must be newer than 1967 and a WideCase-model !
" Reads something like 2.2 across the red and yellow. "
____ While I currently don't recall the exact resistance-levels for w-c/6-pole alt.stators, your 2.2-ohm reading seems close enough for half of all the stator-windings. _ So if all is as it ought-to be, then you should also get a reading of about 4.4-ohms between the two yellow-wires, (and-also, you should find there to be NO continuity to ground with any of the three wire-leads !).
" The monza is 2 wire, black and red "
____ Most n-c.Monza-models have a pair of yellow-wires, but I do know that a fair number of them rather came with 1-red & 1-black (for some unknown reason) ! _ And it was smarter when Ducati didn't make both alt.stator wire-leads the same color, as only one of them supply a power-pulse that's phased 'in-time' with the ign.spark-timing !
" and has a similar reading. "
____ Well, "similar reading" is just-barely acceptably true,, but, it can't actually be the very-same ! ...
__ With the n-c.version of Ducati's 6-pole alternator, the equivalent reading should be between either of it's two wire-leads & 'ground' (rather than the w-c.red-wire),, and should pretty-much be 2/3rds as many ohms. _ So-thus an ohm-reading taken between your black-wire (or red-wire) & ground, should be near 67% as high as the reading you got between either yellow-wire & the red-wire of the w-c.stator (in your WideCase-Scrambler).
And-so likewise, an ohm-reading taken across the red-wire & black-wire, should be two-thirds as high as the reading you'd get between the two yellow-wires (of the w-c.stator).
So therefore if your black & red n-c.wire-leads provide an ohm-reading of nearly 3-ohms across them, then you can fairly assume that everything is pretty-much testing-out as it all should (with both of your Duke's stator-coils).
__ Please let us know if you find any readings that don't jive-up.
Duke-Cheers,
-Bob
[quote= tobydmv ... " I have a 3 wire stator here on the scrambler. "
____ Indeed, as all 'Scrambler' models were produced with 3-wire alt.stator-cables !
" Looks like 2 yellow wires and one red. "
____ Since you've found two yellow and no white-wire, then your Scrambler-model must be newer than 1967 and a WideCase-model !
" Reads something like 2.2 across the red and yellow. "
____ While I currently don't recall the exact resistance-levels for w-c/6-pole alt.stators, your 2.2-ohm reading seems close enough for half of all the stator-windings. _ So if all is as it ought-to be, then you should also get a reading of about 4.4-ohms between the two yellow-wires, (and-also, you should find there to be NO continuity to ground with any of the three wire-leads !).
" The monza is 2 wire, black and red "
____ Most n-c.Monza-models have a pair of yellow-wires, but I do know that a fair number of them rather came with 1-red & 1-black (for some unknown reason) ! _ And it was smarter when Ducati didn't make both alt.stator wire-leads the same color, as only one of them supply a power-pulse that's phased 'in-time' with the ign.spark-timing !
" and has a similar reading. "
____ Well, "similar reading" is just-barely acceptably true,, but, it can't actually be the very-same ! ...
__ With the n-c.version of Ducati's 6-pole alternator, the equivalent reading should be between either of it's two wire-leads & 'ground' (rather than the w-c.red-wire),, and should pretty-much be 2/3rds as many ohms. _ So-thus an ohm-reading taken between your black-wire (or red-wire) & ground, should be near 67% as high as the reading you got between either yellow-wire & the red-wire of the w-c.stator (in your WideCase-Scrambler).
And-so likewise, an ohm-reading taken across the red-wire & black-wire, should be two-thirds as high as the reading you'd get between the two yellow-wires (of the w-c.stator).
So therefore if your black & red n-c.wire-leads provide an ohm-reading of nearly 3-ohms across them, then you can fairly assume that everything is pretty-much testing-out as it all should (with both of your Duke's stator-coils).
__ Please let us know if you find any readings that don't jive-up.
Duke-Cheers,
-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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tobydmv
- Posts: 88
- Joined: Wed Apr 16, 2014 4:59 am
Re: Testing Stator Coils
Bob, thanks for the words. I ordered a flywheel puller and put it to use. I pulled the scrambler flywheel and stator plate assembly. I found that there is indeed a yellow, white, and red wire. The yellow is so faded it appeared white but under the case I could see the color. I found that the wire housing was crimped under the stator plate. Both the yellow and white wire housing was split and making contact with the stator plate. I removed the old wires and soldered new leads on in matching colors. Ran the wires through the tough rubber hose cover and snaked it through the case holes, what a chore. Reassembled with a nos coil and new condenser from napa. The bike fired up first kick.
Thanks,
Toby
Thanks,
Toby
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DewCatTea-Bob
- Posts: 2897
- Joined: Sun Nov 01, 2009 10:53 am
- Location: Near SE side of Lake Michigan
Re: Testing Stator Coils
[quote= tobydmv ...
" I pulled the scrambler flywheel and stator plate assembly. I found that there is indeed a yellow, white, and red wire. "
____ Then your Scrambler was actually a n-c.model, and not a WideCase as I was left to assume.
" The yellow is so faded it appeared white "
____ That's strange,, cuz most-always, the white-wire is the color that rather tends to become sort-of yellowish colored !
" I found that the wire housing was crimped under the stator plate. "
____ That's odd, as the factory should've avoided such oversight ! _ Do you suppose a previous-owner was responsible for that error ?
" Both the yellow and white wire housing was split and making contact with the stator plate. "
____ Which stator-model do you have, '40w' or '28w' ?
" I removed the old wires and soldered new leads on in matching colors. "
____ So were the removed wires still the factory-originals ? _ And if-so, I assume you also replaced the red-wire as well, right ?
__ Wish you had kept us updated as to all your work-steps ! _ As someone probably would've then been able to learn a thing or two.
" Reassembled with a nos coil "
____ Certainly you didn't find a NOS Ducati green-label ign.coil at "napa", so what should I really be left to gather ?
Duke-Cheers,
-Bob
" I pulled the scrambler flywheel and stator plate assembly. I found that there is indeed a yellow, white, and red wire. "
____ Then your Scrambler was actually a n-c.model, and not a WideCase as I was left to assume.
" The yellow is so faded it appeared white "
____ That's strange,, cuz most-always, the white-wire is the color that rather tends to become sort-of yellowish colored !
" I found that the wire housing was crimped under the stator plate. "
____ That's odd, as the factory should've avoided such oversight ! _ Do you suppose a previous-owner was responsible for that error ?
" Both the yellow and white wire housing was split and making contact with the stator plate. "
____ Which stator-model do you have, '40w' or '28w' ?
" I removed the old wires and soldered new leads on in matching colors. "
____ So were the removed wires still the factory-originals ? _ And if-so, I assume you also replaced the red-wire as well, right ?
__ Wish you had kept us updated as to all your work-steps ! _ As someone probably would've then been able to learn a thing or two.
" Reassembled with a nos coil "
____ Certainly you didn't find a NOS Ducati green-label ign.coil at "napa", so what should I really be left to gather ?
Duke-Cheers,
-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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tobydmv
- Posts: 88
- Joined: Wed Apr 16, 2014 4:59 am
Re: Testing Stator Coils
Well Bob, both wires appear to be creme colored, hows that? PO had no clue about electrics or how to remove the mag rotor. Im glad for that since it usually means the wrong tool was used and something gets damaged.
I must commend Ducati for making a very nice little platform/dashboard for the stator coil leads. It made the job of soldering new ones in much easier. I just heated up the junction point and pulled the old wires out one at a time. Then tinned three new wires and pushed them into the hot joint.
I think the wires were stock but they appear to be aluminum, or at least a silver metal that isnt copper. I'm guessing they are stock, since pulling them from the black tubing protection piece removed their clear coat. Like a snake skin....
If anyone is curious I ran the yellow wire to the HT coil. White to frame earth/ground. Red is bound for the headlight. I might get a new wiring harness or just put a switch in place to interrupt the yellow or white wire. I now need to swap the motor to the newly pc'd monza frame. Still need to order some rims and rebuild the wheels. I'm not sure how to handle the hubs. I cant imaging polishing them. I tried polishing the fork lowers and got about 6 hours in and gave up. Maybe i'll sand them down to matte finish with 400/600 paper.
I must commend Ducati for making a very nice little platform/dashboard for the stator coil leads. It made the job of soldering new ones in much easier. I just heated up the junction point and pulled the old wires out one at a time. Then tinned three new wires and pushed them into the hot joint.
I think the wires were stock but they appear to be aluminum, or at least a silver metal that isnt copper. I'm guessing they are stock, since pulling them from the black tubing protection piece removed their clear coat. Like a snake skin....
If anyone is curious I ran the yellow wire to the HT coil. White to frame earth/ground. Red is bound for the headlight. I might get a new wiring harness or just put a switch in place to interrupt the yellow or white wire. I now need to swap the motor to the newly pc'd monza frame. Still need to order some rims and rebuild the wheels. I'm not sure how to handle the hubs. I cant imaging polishing them. I tried polishing the fork lowers and got about 6 hours in and gave up. Maybe i'll sand them down to matte finish with 400/600 paper.
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DewCatTea-Bob
- Posts: 2897
- Joined: Sun Nov 01, 2009 10:53 am
- Location: Near SE side of Lake Michigan
Re: Testing Stator Coils
[quote= tobydmv ...
" both wires appear to be creme colored, "
____ Usually ya can tell which is which by scraping-off the outer oxidized layer and-then reveal the original yellow and white coloring of the stock wire-lead's insulation.
" I think the wires were stock but they appear to be aluminum, or at least a silver metal that isnt copper. "
____ That's indeed consistent with the crumby factory-stock wire-leads !
" I must commend Ducati for making a very nice little platform/dashboard for the stator coil leads. It made the job of soldering new ones in much easier. "
____ You should've let us know what you were considering back-then when you were replacing the wire-leads, (so that you could now possibly chose any electrical-scheme that you'd most prefer).
" I ran the yellow wire to the HT coil. White to frame earth/ground. "
____ That circuit-wiring is only consistent with the '40w' alt.mag wiring-scheme,, so if your ignition doesn't work with the white-wire ungrounded, then you indeed have it all correctly connected ! _ However if leaving the white-wire unconnected to anything makes no difference to the operation of the ign.system,, then you have the '28w' alt.mag-stator, and it's white-wire is supposed to be for a battery charging circuit.
__ What about a brake-light, got any plans for that ?
" Red is bound for the headlight. "
____ That's fine, as that's the proper lighting-circuit for either the 40w.type or 28w.type stock wiring-schemes !
Let us know how satisfied you are with the strength of the headlight-brightness.
" I might
put a switch in place to interrupt the yellow or white wire. "
____ A key-switch installed that way (at-least on the yellow-wire) would do quite well-enough as an ign.cut-off, to keep others from starting-up your Duke.
Duke-Cheers,
-Bob
" both wires appear to be creme colored, "
____ Usually ya can tell which is which by scraping-off the outer oxidized layer and-then reveal the original yellow and white coloring of the stock wire-lead's insulation.
" I think the wires were stock but they appear to be aluminum, or at least a silver metal that isnt copper. "
____ That's indeed consistent with the crumby factory-stock wire-leads !
" I must commend Ducati for making a very nice little platform/dashboard for the stator coil leads. It made the job of soldering new ones in much easier. "
____ You should've let us know what you were considering back-then when you were replacing the wire-leads, (so that you could now possibly chose any electrical-scheme that you'd most prefer).
" I ran the yellow wire to the HT coil. White to frame earth/ground. "
____ That circuit-wiring is only consistent with the '40w' alt.mag wiring-scheme,, so if your ignition doesn't work with the white-wire ungrounded, then you indeed have it all correctly connected ! _ However if leaving the white-wire unconnected to anything makes no difference to the operation of the ign.system,, then you have the '28w' alt.mag-stator, and it's white-wire is supposed to be for a battery charging circuit.
__ What about a brake-light, got any plans for that ?
" Red is bound for the headlight. "
____ That's fine, as that's the proper lighting-circuit for either the 40w.type or 28w.type stock wiring-schemes !
Let us know how satisfied you are with the strength of the headlight-brightness.
" I might
put a switch in place to interrupt the yellow or white wire. "
____ A key-switch installed that way (at-least on the yellow-wire) would do quite well-enough as an ign.cut-off, to keep others from starting-up your Duke.
Duke-Cheers,
-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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tobydmv
- Posts: 88
- Joined: Wed Apr 16, 2014 4:59 am
Re: Testing Stator Coils
Bob, I thought I'd post a follow up. The light coil seems extremely weak in output. So i'm afraid you are correct (Let us know how satisfied you are with the strength of the headlight-brightness)...I put a small CEV test lamp on the light coil output wire and it barely made the element glow at idle speed. Appears that the scrambler is equipped with the 28w unit. But i'm off for bigger fish now. The bike idled perfectly for about 5 - 10 minutes and then died and wont restart.
So I had a look at the valve clearance/lash and the intake had no clearance between rocker and valve shim at TDC. The exhaust was around .0016". Removed the head and dissasembled. The intake valve seat has some small abrasions that are probably beyond lapping. The valves were really tight in the guides and when removed had some bronze dust on them. Looks like i'm headed for a head rebuild. Would anyone happen to know what size valve cutter the scrambler head needs? Also, any thoughts on the valve kits from Eurotrash? The price is very good and appears to be Kibblewhite parts.
Thanks,
Toby
So I had a look at the valve clearance/lash and the intake had no clearance between rocker and valve shim at TDC. The exhaust was around .0016". Removed the head and dissasembled. The intake valve seat has some small abrasions that are probably beyond lapping. The valves were really tight in the guides and when removed had some bronze dust on them. Looks like i'm headed for a head rebuild. Would anyone happen to know what size valve cutter the scrambler head needs? Also, any thoughts on the valve kits from Eurotrash? The price is very good and appears to be Kibblewhite parts.
Thanks,
Toby
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