Motoscrubs.com

Hi all,

This lovely little 250 is owned by a friend of mine who asked me to ask a few questions on his behalf about it ('cos he asked me and I can't answer them!)...





It was imported from the US. The frame number is 84793 and engine number 84452. Obviously, it has been restored. It has the SS1 29 carb, high compression piston, a very "hot" cam (that is pointless for normal street riding!) and kit megaphone fitted (ditto!). Firstly some more pics...













And now for a few questions...

The engine number prefix is DM250 rather than DM250M3. It is unclear to me from my reading if the early Diana's exported to the US had the M3 notation (from my reading it may be that this didn't happen until the release of the Mach 1 and it's M1 notification - but it isn't clear). How do these numbers sit with it being an original 64 Mark 3? (EDIT: It's not even clear to me from my reading when the "Mark 3" name became "official") To be clear, the purpose of the question is merely intellectual interest and education.

Secondly, the owner believes it has no AAU in place (nor kickstart for that matter). I recalled Jim's Mach 1 questions regarding same and read through that. See that post here:

http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=1013&p=6897

The owner is interested in getting it to "road mode" by installing a kickstart and an AAU and I note DCT-Bob stated that the 18 degree unit should function fine in there without modification. Do I have that correct? I think I have such an AAU spare I can give him and just wanted to check if the ID number AA367B is the correct 18 degree magneto unit.

Regards,

Kev

" This lovely little 250 is owned by a friend of mine who asked me to ask a few questions on his behalf "

____ He's more than welcome & ought to join-up with us (for direct interaction with this w.site).



" It has the SS1 29 carb, high compression piston, a very "hot" cam
and kit megaphone fitted "

____ The non-stock carb (& other of such) may perhaps be from an installed factory race-kit, Or a previous-owner may have tried to emulate such.



" The engine number prefix is DM250 rather than DM250M3. It is unclear to me from my reading if the early Diana's exported to the US had the M3 notation "

____ I'm quite certain that the suffix 'M3' was not included on any 'Diana Mark III' motor before the '250Mach I' model went into production for the 1965 model-year.



" How do these numbers sit with it being an original 64 Mark 3? "

____ The given motor-number is fairly consistent with the 1964 model-year.
However all publications I ever recall refer to the specific name as 'Diana Mark III' , not "Mark 3" !



" It's not even clear to me from my reading when the "Mark 3" name became "official") "

____ I've discussed this particular issue once or twice before...
__ I recall seeing mag.ads by the U.S.importer -('Berliner'), which even after the 1964 model-year, continued-on referring to the 'Diana' name for the 1965 & 66 250 Mark-3 models. _ But certainly by the time the w-c.250 Mark-3 models came-out, the Diana-name had become officially dropped.
So the importer much contributed to the blurriness of exactly when the model-line actually got it's name officially changed to simply "Mark 3". _ Some old Duker in Italy ought to still be aware of the exact year when the name-change ACTUALLY took effect officially by the factory.
However I surely expect that the owner's-manuals from all the years that model-line was produced would certainly help clear-up the issue. _ I say "help" because I happen to know that the factory was not very careful to exactly match-up owner's-manuals precisely to the particular model-year, from year change-over to year,, (in other-words, your brand-new 1964 Mark-III might've come with a left-over 1963 owner's-manual, when purchased earlier in the 1964-year).
The pre-1965 Mark-III never exhibited any clue of the 'Mark 3' title/name,, and not until the model-line came with the newly-added (for 1965) side-cover/tool-boxes, was there then any obvious clue to the model-name being altered from 'Mark III' to 'Mark'3' ! _ So (in my view), it's pretty-obvious that the Ducati-factory pretty-much officially changed the 'Diana Mark III' model-line's title-name to "250 Mark 3", beginning for the 1965 model-year !
And that stands to very-good reason, as the 1964 to 1965 model-year change-over then exhibited major-changes of that model-line,, as that was exactly when the old Mark-III top-end was eliminated & replaced with the 'Mach-I' top-end !



" the owner believes it has no AAU in place
and I note DCT-Bob stated that the 18 degree unit should function fine in there without modification. Do I have that correct? "

____ Yes... after installation, ya just have to reset the static-ign.timing (from about 39) to 20 ~ 23-degrees BTDC.



" wanted to check if the ID number AA367B is the correct 18 degree magneto unit. "

____ I never memorized those designation-numbers but, ya can discern the correct AAU (for the energy-transfer type ignition) by noting that it's points-cam's lift-lobe only spands for about 1/3rd of it's total 360-degree duration, (where-as the battery-powered AAU-type is pretty-much just the opposite).
__ Here's a link to what the one you want should look like... viewtopic.php?f=3&t=757&hilit=AA367B#p5214
And here's a link to another picture showing the AAU which you DON'T want... viewtopic.php?f=3&t=757&p=6863&hilit=AA367B#p6863


Duke-Cheers,
-Bob

this bike is fitted with a 4 speed engine . i thought that a 1964 should be fitted with a 5 speed engine

anyway i never seen a 4 speed crankcase stamped DM 250 M3 .

Eldert

__ Here's a link to what the one you want should look like... [url]viewtopic.php?f=3&t=757&hilit=AA367B#p5214[/url]

Yep, that's the cam profile I have on the three AA367B's I have - with much less time of the points being held open compared to the 28 degree version (AA359). I did test both with a degree wheel and they give 9 degrees and 14 degrees of points advance on the timing gear, but wasn't sure if there were other other cam profile options for each AAU as well. Thanks for that, Bob.

this bike is fitted with a 4 speed engine . i thought that a 1964 should be fitted with a 5 speed engine
and...
anyway i never seen a 4 speed crankcase stamped DM 250 M3

Hi Eldert, how did you arrive at that 4 gear assessment. Is that by engine number? I discussed with the owner before posting my initial post that this bike may be one of the initial exports that actually led to Berliner's "Mark III" title....ie it was a Diana with a race kit but predated the Mach 1 and '64 5 gear models. The other thing that points me towards that is the tail light. IS there anything to be learned from the (poorly focussed) shot of the underside of the tank? The tunnels underneath are non symetrical with a larger tunnel over the carb side.

Thoughts?

Kev

Hi Kev

DM 250 suffix on rh crankcase is 4 speed . 5 speeders had the DM 250 on the lh crankcase



Eldert

Thanks Eldert. Another snippet of Ducati information I'll have to invest some brain neurons and synapses in!!!

Kev

By: Eldert...
" this bike is fitted with a 4 speed engine . i thought that a 1964 should be fitted with a 5 speed engine "

____ Eldert is right to bring that inconsistency into question !
As the 4-speed motors were phased-out in 1963.
So-therefore Duke-motors actually produced in 1964 were all 5-speed models.
__ This is the kind of confusion that comes from Dukes having not been finally sold (in the U.S.) within the very same year in which they were actually produced at the factory. _ Often Duke-models were held-over from the year they were actually produced and then later passed-off as a model of a following year.
That's why my chosen wording was careful to not state that the Duke in question was actually MADE in 1964.
So if this Duke-model in question came with a 1964-title, then that's the reason why, (even though it was possibly actually built at the factory as early as late 1962.
__ In my previous posting, I had meant to mention something about whether it was a 4 or 5 speed motor,, but as usual, (by the time my PC gets-over one of its constantly occurring freeze-up fits), I forgot to include that additional thought/tidbit at the time I posted.
And the fact that all your posted-pix have their right-sides cut-off from view, kept me from seeing the area where the motor-case numbers are expected to be seen (so as to possibly have been reminded to included that added tidbit).


Stay-Tuned,
-Bob

Hi Kev
another thing your friend has to watch is the clutchcover . the one thats fitted is from a 175 / 200 engine .
unless material is removed from the inside of the cover every time the clutchlever is pulled and the pressure plate moves outwards the pressureplate is grinding up against the cover

Eldert

" the one thats fitted is from a 175 / 200 engine . "

____ Eldert is right !


" the pressureplate is grinding up against the cover "

____ Such interference damage may not be occurring, as some race-minded owners sought to lighten the motor by substituting the lighter cover and employing one less clutch-plate pair, (for only 6, instead of 7).


Dukaddy-DUKEs,
-Bob

By: machten...
" I discussed with the owner
that this bike may be one of the initial exports that actually led to Berliner's "Mark III" title....ie it was a Diana with a race kit but predated the Mach 1 and '64 5 gear models. "

____ Other than their vastly different electrical-systems, a Mark-III ought to have a Motocross/Scr-cyl.head which has a 2mm larger-diameter intake-port than a Monza-cyl.head (which the Diana-model employed also as well).


" The other thing that points me towards that is the tail light. "

____ The earliest Mark-III model did not have any means for a brake-light !


Duke-Cheers,
-Bob