Recharging 250 MK1/MK3 Magneto

[DewCatTea-Bob]

By dsmess : ...
" I was fixating on some web info I saw awhile back. You may have seen it. This guy modified a Ducati single case. He was using this rig to test Stators. "

____ No I've been unaware of that! _ And I sure would like to know more about it!
Can you find that particular web.info again for us?


" Did you see my posting on the Electrex setup? "

____ Yes of course, and I also just added my 2cents-worth to that thread... Had started-out with intent to just add a comment or two, but got carried-away as I often do!


GoodCheers,
-Bob

[Pete]

Here is that test rig

http://www.ducati.ms/forums/showthread.php?t=62366

Pete

[DewCatTea-Bob]

By captpaul : ...
" I have 8 brass wheels 4 are weak "

_____ There was a time back in the late '70s when I had at least that many spare flywheel-rotors collected (within a single heavy-duty box)!
___ As you're no doubt aware, each flywheel has a 'timing-mark' on the front side of the brass or aluminum face of the rotor. _ The timing-mark is in the form of a short vertical line -(about 12 to 15mm in length).
(A good DUKE-mechanic knows to always take careful note of the exact position of that mark [in relation to TDC] BEFORE pulling the rotor from the crankshaft!)
__ After I began to gather a collection of these rotors, I then noticed that the 'timing-mark' was not always placed in the exact same position of the rotor, in relation to the placement of the magnets! _ (Which doesn't make good sense!) _ But it seems to me that the so-called "timing-mark" should be placed so as to EITHER indicate exactly where the rotor should be directly-aligned with the TDC-slot (in front of the tapered-shaft which the rotor is pressed onto), OR else, indicate the exact point where MAXimum magnetic-flux of the rotor is located. - (NOTE: In the case of the 4-pole rotor, there would be 4 such locations [spaced 90-degrees apart] where a mark could be placed to indicate the MAX-flux,, and in the prior case, in which The MARK could represent the required 'TIMING' to the crankshaft, there could be 2 locations [spaced 180-degrees apart) where the mark could be placed !
Yet it seems that Ducati did not consistently maintain either of these two logical locations to place their rotor-markings!! _ (As I mentioned in another post, it SEEMS that Ducati chose some method, (or lack thereof), of rotor MARKing-placement so as to totally confuse ANY unwise mechanic !)
___ Anyhow, could you please look-over your 4 to 8 rotors and make careful note as to how the 'timing-mark' on the face of each rotor relates to the position of the magnets on the back-side ?
To do that job, I myself would simply use a L-shaped straight-edge to carefully guide a scratch (made with a scriber-tool), so as to make an accurate extension of the 'timing-mark' around to the back-side of the rotor, to then make note of the scratch-mark in relation to the position of the nearest two magnets.
Completing this job on more than 2 (otherwise identical rotors), I'm sure you'll fine no rime-or-reason for the exact location of EVERY such timing-mark which you check. _ (And I'll be surprised if you happen to find more than 2 rotors with their marks located in the exact same relative position!)
__ Please be so kind as to let us all know, (and everyone else who can do so, as well)!


Thanks,
-Bob

[captpaul]

Ian (VELLO TWIN)
I'm sending 2 mk3 flywheels to a man in Kentucky to have them magnetized.
When I get them back I'll let you know the quality of the workmanship and
price. cheers Capt Paul

[captpaul]

Dew Cat Tee Bob
I checked some mk3 and scr flywheels ie 40 watt till motor #92171, flywheel # 31 20 94 stator # 31 95 416
And my factory parts book says, from 92172 on(1966) they were scr models ie 28 watt flywheel #3195471, stator#31 95 472
The wheel 31 20 94 and a wheel 31 20 92 although they looked the same the timing mark was in between magnets,
and the other was at the beginning of a magnet, I believe they are only marked (timing mark) differently to fit a certain application,
and are really the same.
I have to look for the 31 95 471 wheel for my 1968 scr (Berliner sold leftover 1966 scr's and marked the year of the bike when he sold them)Title says1968 but it's a 1966. I can't set the timing till I find the 28w flywheel.
I'm glad you pointed this out, as I would have gotten the timing wrong, because I took flywheels off, and put them in a box a long time ago.I should have marked each with a marker as I took them off.
I have an unusual one, it's 5" wide 6 magnets,brass, and is marked with all the Ducati markings part #31 44 92,can you help me identify what it would fit.My master parts book only goes 1964-1966 model years, I need some one with a parts book from1960- 1963 to get the right magnetos for 1962 250scr and the1963 mk3, you're the man Bob Thanks a lot!!

[DewCatTea-Bob]

____ Thanks for the useful report c.Paul !
__ I hope that others will also report about their flywheel-rotors as well ! _ Cuz as the associated old/pre-1967 chart-listing (now posted down-below) seems to indicate, there were a somewhat dizzying number of differing alt/mag.rotors apparently produced with their stamped timing-marks left questionably located !


" (Berliner sold leftover 1966 scr's and marked the year of the bike when he sold them)Title says1968 but it's a 1966. "

____ Right, that's been my understanding as well ! - (Including the Sebring & other narrow-case models as well !) _ And not just simply because there just happened to be 1966 left-overs... It's clear that Berliner planned it that way ahead of time,, as most all of us have noted that the foil-tags on the neck-front of the frames, left the last digit of the model-year blank, (thus the "196 ").
Ducati may have produced the 160 after 1966 but, starting for the 1967 model-year, Ducati switched-over the 250 & 350 production to the wide-case model-versions. _ So anyone who has a "67" or "68" narrow-case model, actually has a Duke which was really produced in 1966.


" I should have marked each with a marker as I took them off."

____ Right ! _ That's a common oversight !
I always tell others to be sure to add a scratch-mark onto the rotor's taper-mount, directly in-line as above the drive-gear's key-way slot (representing TDC), before pulling the mag.rotor off (from any factory-stock engine), so that the original factory-set phasing won't be lost ! _ But most forget to remember to perform that good-measure anyhow. _ Even I-myself had never bothered to make any such note (before I discovered that their original timing-marks were not actually trustworthy), as ya just naturally assume that the factory had everything properly set & correct to begin with !
But after comparing a fair number of otherwise identical alt.rotors and then finding that their timing-marks were almost completely inconsistent (even from the same model-year), I then came to realize that I should-not trust that the original-marks were actually set for the purpose of optimum ignition-timing, (or any consistent purpose what-so-ever). _ Thus the only answer that makes sense for the inconsistent marking placement (on at least some unknown number of rotors), is ERROR by those in charge of the marking-process back at the time.
So I had to try to figure-out which timing-marks were correctly placed and then determined that MOST were not properly located for optimum synchronization with the ignition's static-timing. - There is no other apparently logical reason for placement of The-MARK elsewhere on the rotor-face, (and even if there were, it seems that there was never any agreement about it that remained consistent).
Thus I had to come-up with an easy method to accurately place a replacement-mark in a rather LOGICAL location.
I'll explain it as soon as someone needs to know, (maybe sooner).


" I have an unusual one, it's 5" wide 6 magnets,brass, and is marked with all the Ducati markings part #31 44 92,can you help me identify what it would fit. "

____ Gee, I've never seen a small sized "brass" rotor with "6" magnets on any Duke ! _ Are you sure it's from a narrow-case single? _ Or are you unsure of exactly what motorcycle it came-off from ?
Cuz Ducati's electrical power-plant department did produce alternators for other motorcycle-companies as well !
__ Do you have any other 6-pole alt.rotors which you can further compare it with ?


Tillater,
DCT-Bob

[captpaul]

Dew Cat Tee Bob

When I find the box With the 60watt flywheel(aluminum) and stator,I'll compare them with the larger brass 6 magnet one.Paul

[DewCatTea-Bob]

By Desmoto-M.3 : ...
" can you tell me the auction number of the advancer you're talking about "

____ Well Ken, since you seemed to possibly be interested in the 18 to 28-degree advancer-unit swap-over modification, I'm placing a link here below to an auction, (which ends today), for one of the 28-degree units.

http://cgi.ebay.com/ebaymotors/ws/eBayI ... EBIDX%3AIT

Sorry for the short notice but, I just happened to notice it listed while doing a search at eBay to see what all DUCATI-items are listed to end today. - (Something that all smarter eBay-sellers do, cuz SUNDAYs have become the best day to have an eBay-auction end.)


Fun-Cheers,
-Bob

[Desmoto-M.3]

Darn, i missed it Bob! Can't believe it sold for less than that other one too! I would have bid higher than that. I guess i should keep closer watch here at this website more often.
I had been thinking of asking if anyone knew of any place where i could get a 28 degree advancer from.
But if i did get one, installing it completely right would probably exceed the limit of my current abillity anyhow, because even though i know how to reset the points gap well enough, i have never had to reset the static timing before, and from what I've seen about how it's supposed to be accomplished, I'm really not too interested in having to do what's all involved to get that job done.

I do plan to use your method to charge a 6 volt battery for powering a horn and the brake light, and since i understand that the required rectifier for that job will also spare the ignition coil from too much electric current like the stock 18 degree advancer's cam is meant to do, I figure it would be good reasoning to also go for replacing my advancer with a 28 degree version.

I have been anticipating your explaination on how to modify a 40watt alternator to help with the dim lighting situation which so equiped models suffer from during low rpm running.
About 3 weeks ago in another thread you said you would post your related info, possibly within another thread. Did I somehow overlook where ever you placed that post?

Thanks for your guidance.

Ken

[DewCatTea-Bob]

" i have never had to reset the static timing before, and from what I've seen about how it's supposed to be accomplished, I'm really not too interested in having to do what's all involved to get that job done. "

____ You're right that the static-timing would need to be checked after installing a different advancer-unit ! _ And although you'd have a large setting-window -(of 8 to 13 degrees BTDC), to target for,, you really shouldn't let the installation-job go without being fairly sure of where your static-timing ends-up being set at.
I agree that it's a bit of a time-consuming job, just to check the static-timing, (compared to Jap-bikes).


" I do plan to use your method to charge a 6 volt battery for powering a horn and the brake light, and since i understand that the required rectifier for that job will also spare the ignition coil from too much electric current like the stock 18 degree advancer's cam is meant to do, I figure it would be good reasoning to also go for replacing my advancer with a 28 degree version. "

____ That's right! _ Except for my first-time -(adding a battery to a '40watt-system'), I always made both those changes together, (even though not necessary).


" I have been anticipating your explaination on how to modify a 40watt alternator to help with the dim lighting situation which so equiped models suffer from during low rpm running. "

____ After adding a battery, I then once also added an extra bulb through the headlamp's reflector, and wired it to light-up when-ever the brake-light came-on. _ That was my first attempt to help the dim headlight concern... As I had had too many drivers holler at me that there was something wrong with my lights, while stopped near intersections at night!


" About 3 weeks ago in another thread you said you would post your related info, possibly within another thread. Did I somehow overlook where ever you placed that post? "

____ No, I haven't done that yet... I keep putting it off cuz I always seem to find something else more urgent to post on, when-ever I find some time to do so.
I'll try to get back to that subject soon.


DUKE-Cheers,
DCT-Bob