1968 250 MK3D rebuild - ex W/C Oil Pump

[wcorey]

I much hope to post pix & confirm figures,

Well I though it was pretty cool that you had seen such a cam, I'm doubly impressed that you actually HAVE one! I'd be very curious to see the timing specs, though I suppose it would be a pain to do. You should change your title here from 'moderator' to 'curator', lol.

...as soon as it warms-up enough for me to try & un-bury decades of accumulations in our (unheated) basement.

I know what that's like, in both basement and garage. As a consequence of years of buying misc boxes of parts at swap meets, I often find stuff I didn't know I own...

I sold the extra one to a fellow DIOC-member who's son I gather sold it to someone who then listed it on eBay a year or two back !
Too bad you must've missed that, as the seller confirmed the incredible lift of it !

While I've owned my R/T for 20 years, I didn't really start delving into it until last year so wasn't really actively looking for singles parts before then. In any case I don't think I'd want to see what such a cam would do to my valve train, I find it pretty wild that Ducati would have considered putting them in standard available models.


Bill

[DewCatTea-Bob]

" Well I though it was pretty cool that you had seen such a cam, I'm doubly impressed that you actually HAVE one! "

____ I would not have dared so stretch my credibility stating such far-out lift-figures, if I didn't actually have one of those incredible D.cams to back-me-up.
__ Also I had noted that there were two separate listings on eBay (sometime between spring-2009 & summer-2010) for the Grey&White-D.cam, I don't know if it was the very-same cam or not, (sold by two different sellers), but one of the listings pointed-out that it's lift was over 1/2 inch !
(Too bad that all 3 or 4 owners of of those G&W-D.cams are not active posters here!)


" I'd be very curious to see the timing specs, though I suppose it would be a pain to do. "

____ I think I was once given the timing-specs for at least one of those two special D.cams (and should still have them recorded somewhere). _ I was told that the R&W-D.cam's valve-timing was pretty-much the same as the 1973-750SS (but not exactly). _ (Kev, do you happen to have the bevel-750SS v.timing handy?)
John White had also told me that the special 450D.cam had more lift but less duration, since the 450-engine could not "breath" well enough to rev as high (as the 350)!


" In any case I don't think I'd want to see what such a cam would do to my valve train, I find it pretty wild that Ducati would have considered putting them in standard available models. "

____ I believe it was the first time I got to talk to John in person (rather than by expensive 'long-distance'), that after asking him if a 350F1D.cam would fit/work in my 450D hot-streetbike project, he then mentioned that a much better choice for a cam would be the "special 450-DESMO cam" ! _ And it was he who then at that time explained to me why they were "Special" and not found within the standard parts-books ! _ He also went-on to explain that the special 350 & 450 D.cams were based on the D.cams* of the 350 & 450 factory-racer engines, (* of which were not only unstreetable, but also much harder to obtain & excessively expensive !)
I asked him if there was also a "special" D.cam for the 250D, as well,, to which he replied: "No, because the Blue&White IS the special cam for the 250D !" .
I then asked if he knew of anyone having tried the R&W in a 250D, and he said yes but without really worthwhile/great results, as it's wilder v.timing was unnecessary for that small displacement.


____ (I may add more similar details to this post after I recall more of such.)


Dukaddy-DUKEs,
-Bob

[machten]

I was told that the R&W-D.cam's valve-timing was pretty-much the same as the 1973-750SS (but not exactly). _ (Kev, do you happen to have the bevel-750SS v.timing handy?)

I'll be able to dig them up, I think.
EDIT - and now have.

There is the stock camshaft from the (very few - like count on one ot two hands) 73 "black case" greenframes, the more "common" 74 ones, and the 72 racing version referred to as the Imola cam.

The 73 Greenframe was homologated with the 1972 Imola cam. It had valve sizes at I:42mm E:38mm. Lift was I:12mm, E:11mm. Cam timing is +/- the 5% all duc twins were specified with at:
I Open: 65 BTDC I Close: 95 ABDC
E Open: 95 BBDC E Close: 60 ATDC

The 74 Greenframe was homologated with a new cam. It had different valve sizes at I:40mm E:36mm. Lift was I:11mm, E:11mm. Cam timing is +/- the 5% all duc twins were specified with at:
I Open: 63 BTDC I Close: 83 ABDC
E Open: 80 BBDC E Close: 58 ATDC

The 1973 Imola "short stroke" race bike may have had a different cam again and very little is documented about it that I've found and i don't have those particular details. I do have living a few km away from me mandrels for actually producing the 72 Imola cams!

The corresponding VeeTwo (street) camshaft specs are below...

Cam Timing Figures for Vee Two Camshafts
Suit: Ducati Bevel Drive Desmo Engines 750 Roundcase
Part Number: V2-03-054
NB: All figures checked with running clearance. Opening and closing figures checked at 0.5mm lift.
Inlet opening 48 BTDC
Inlet closing 82 ABDC
Exhaust opening 80 BBDC
Exhaust closing 46 ATDC
Maximum lift inlet 12mm
exhaust 11mm
Running clearance inlet .1mm
exhaust .15mm
NB: When checking timing figures in Desmo engines not using closing springs, ensure that the
bottom rocker is held up against closing shim at position of taking cam timing figures.

Sorry for all that twins info, but you did ask and the answer was necessarily a bit less simple than the question

Re: 16mm lift....gee, reckon they'd go through standard Ducati valve guides quickly!!!!

Kev

[machten]

Just responding to some earlier points. I got busy at work and didn't have time earlier...

While you've been supplying quite useful as well as not so useful measurement-figures of all your well measured D.cams, an omitted measurement-figure that's of importance for any non-standard/B&W D.cam, is the overall-size of the 'D-shape' -(of the closing-lobes)! _ Cuz when that 'D' gets too large, it then can't fit into/through the stock cam-tunnel (even when the shaft-center is not properly-aligned) !

Not sure what you're alluding to here Bob. See my max figures provided for the Desmo closer lobe. Am I missing something? All the max com lobe figures provided are under my tunnel sizes (just).

____ That's just fine as well, especially if done along-with that which I've suggested. _ Otherwise, show me four guys (who each had taken a test-ride alone), with a few fresh beers under their belts,, and I'll then (separately) show you four guys with differing opinions.

Fair enough. I guess I'm willing to sacrifice the "science" for some fun. Not only that, but the serious experience I have available to me, I suspect most others dont have. I'm happy with informal feedback as a reasonable measure. I'm not talking newbies here. So here's two of the four riders...

Here's one of Marco's bikes we're messing with now for race prep (A genuine 46 Gilera factory racer and an experienced CAMS accreditied Ducati singles race rider)...

Picture 092.jpg

Bob O'Leary (rhs of grid) - Western Australian (multiple times) and Australian Speedway Champion, WA Motocross Champion (multiple times), WA Road Race Champion...

1084984312_ju5dw-M.jpg

I'm happy I'll get some fair and balanced assessment from these guys - and the fun of some crack afterwards! (and check out the leaving of the start line of a speedway champion. He didn't leave early, look where he is compared to the other guy with (purposely) front wheel just grounded and body weight forward.)

____ So then there's possible additional reason to prefer to test-out the V2-d.cam first.

I'm going to take the approach of running stock first because I'm going to be messing with carb and ignition timing beforehand.I don't want the complication of an "odd" cam whilst I do that first.

" Except for the fact that it is a DESMO cam!! "

____ But just "White" doesn't make any sense cuz most all DESMO-cams include 'White' within their color-codes ! ... Such as: Blue&White for the 250D.cam ; Red&White for the 350D.cam ; & Grey&White for the 450D.cam !
So may as well not even mention any color at all, as state it's a "White" DESMO-cam ! _ (And I'm sure there was never any White&White-D.cam [by the factory].)

Yes. that was exactly my point. The comment about not being totally true to name was about a scramler club selling a desmo cam (and rockers, spindles, bushes etc), but I'm grateful they do,

Kev

[DewCatTea-Bob]

" Not sure what you're alluding to here Bob. See my max figures provided for the Desmo closer lobe. Am I missing something? All the max com lobe figures provided are under my tunnel sizes (just). "

____ Sorry Kev, it seems that I'm the one who was missing something ! ... When I looked-over your cam-lobe measurements, I had failed to make specific note that your listed max.closing-lobe figures were so very close to that of the cam-tunnel's diameter (which I also failed to bother to recall the size of - which I'm now recalling to be just 42mm, correct?).
Anyhow, I had only really paid attention to just your bottom-line lift-figures, and had jumped-assumed that you had figured your closing-lobe lift-figures by subtracting the minimum-radius from the maximum-radius. _ But now you've lead me to realize that you may have actually gotten your closing-lobe lift-figures by the very-same method most used to figure the lift-figures of the OPENING-lobes !? _ And if so, I should mention that it's doubtful that figuring closing-lobe lift-figures can be fully trusted done by that (likely unprecise) method. ...
__ The only really trustworthy method for getting the lift-differences of closing-lobes, is with the use of the dial-indicator method.
__ So if you've already been stating the 'peak-to-peak' measurements of all the closing-lobes, then of course you've already been supplying the particular figures which I had before assumed you had been omitting.
__ To better clarify what I meant previously...
While the closing lobes actually don't look exactly like a "D", they're fairly close to that shape,, and when the shaft (of the cam) IS "properly-aligned" (through the center of it's two support-bearings), then the outer-radius of the 'D'/closing-lobe "(just)" barely clears the cam-tunnel's wall (with std.sized D.cams), due to it's lift-size (which you've been obtaining with the measurement of the WIDTH of the 'D' ). _ But since the shaft/'D' doesn't really need to be kept "properly-aligned" WHILE merely being inserted-THOUGH the cam-tunnel, this thus allows some jiggling for slightly more space to clear the cam-wall by,, thus making the HEIGHT (rather than the mere width) of the 'D', the actual measurement to be concerned with whenever in reference to larger than standard D.cams. - (BTW, it's of course just a coincidence that I use a capital- D for both Desmo & the shape of the closing-lobes.)
__ So it seems that the "something" YOU were "missing", is the alternate reason for measuring the closing-lobe's tip-to-tip figure, (which ought be a bit less than twice that of the max.radius).
Knowing of this particular D.cam measurement, lets ya know if any non-standard D.cam requires either slight, (as is the case with the R&W), or major, (as is the case with the G&W), modification of the cam-tunnel !
(I've added a pic to help clarify all the differing space-measurements concerning the closing-lobes, so that we can now be more sure of what we're referring to.)
__ Anyway, if you could (directly) compare the peak-tip to peak-tip figures (of the D), of the LARGEST closing-lobe of your VeeTwo & stock D.cams, then that may also be of use to know of.
__ (Sometimes it's good that others don't understand what an-other has stated, so that one or both will (unnecessarily) do some extra-thinking which could lead to new-thoughts which otherwise wouldn't have been thought of !)
Sorry if I've caused you to waste any time exercising your brain !


Clearer-Cheers,
-Bob

[machten]

Sorry if I've caused you to waste any time exercising your brain !

At my age, exercising your brain is supposed to be a good thing, and hardly a waste of time...and yes, you and others are doing that to me! By the time this little thread is done I ought to be a damn genius

I'll go back and have a look at the measurements. I realise dial gauging is the only "true" way to do it, and I'd like to do that but just haven't had the time, so settled for an approximation. I might get time to do a few of them though (perhaps the V2 and a stock W/B. If I can, I will.

Oh! and yes 42mm is what I measured the tunnel at.

Kev

[DewCatTea-Bob]

____ First-off, it seems that you must've clicked-on the 'POST REPLY' button rather than the 'QUOTE' button, since your post-title has defaulted back to this thread's main-title.


" I realise dial gauging is the only "true" way to do it, and I'd like to do that but just haven't had the time, so settled for an approximation. I might get time to do a few of them though "

____ Doing THAT likely would help shed some additional light on a couple things, like those figures you've included showing the difference between opening-lift & closing-lift. _ As any new-found difference there would confirm that a cam is not perfect - (since the set closing-clearance doesn't remain same as at TDC). _ In other words, the method you've been using would work just as well as using the dial-indicator method, IF all D.cams had been as "perfect'" as everyone would've expected them to have been.


" and yes 42mm is what I measured the tunnel at. "

____ Right,, it was quite stupid/ignorant of me to have not made myself fully aware of that fact & ALL your posted lift measurement-figures, before I had placed my post stating that you had omitted a useful figure (which you indeed had not omitted!).
(It seems too many days and pages contributed to that oversight.)


Concerted-Cheers,
-Bob

[DewCatTea-Bob]

" There is the stock camshaft from the 73 "black case" greenframes, the more "common" 74 ones, and the 72 racing version referred to as the Imola cam. "

____ I USED to be quite up-to-date on all the bevel.L-twins, but have since lost my keenness concerning them, (so you may trust other top-sources which don't agree with that which I claim).
As I-myself seem to recall, the 750SS had it's very-own (streetable) D.cam-model, which was not as wild as the 'special' "Imola D.cam" which was based-on/inspired-by the ACTUAL (& nameless) pure-racing D.cam which had been employed during the original (& quite famous) Imola-race.


" The 73 Greenframe was homologated with the 1972 Imola cam. "

____ That's the first I've ever heard of that, as I believe that the special-order 'Imola-cam' had to be especially requested in order to obtain them ! - (At least for here in the USA.)


" Lift was I:12mm, E:11mm. Cam timing is :
I Open: 65 BTDC I Close: 95 ABDC
E Open: 95 BBDC E Close: 60 ATDC "

____ Those figures ring-a-bell for me !
They seem (as best I currently recall) to be the likely figures for the original 750SS models, (which were pretty-much the same as those of the Red&White 350D.cam).
So I'm now thinking that the special 350D.cam's timing-figures were more like 70/95-in. & 90/65-ex., (but don't keep note of these, as they're just a guess at this point!)


" The 74 Greenframe was homologated with a new cam.
Lift was I:11mm, E:11mm. Cam timing is :
I Open: 63 BTDC I Close: 83 ABDC
E Open: 80 BBDC E Close: 58 ATDC "

____ This is another claim which I had never before heard of, plus it seems to me that those stated valve-timing figures are more likely those of the 750Sport & pre-1975 750GT models !

____ So to help clarify that which I've believed, all 750SS-models came-stock with the '750SS-D.cam', and the 'Imola-D.cam' was a special-cam which could be special-ordered for the 750SS, (but was actually not the very exact-same factory-race D.cam-design which was specially-installed & used for the 750 factory-racers which had won the famous Imola-race. _ (I've heard tale of disagreements concerning this "Imola-cam" issue before, claiming that the original/unique D.cams which were employed within the 750 factory-racers [at that Imola-race], were not actually fit-able within unmodified 750SS-D.heads.)
__ In any case, I certainly question your sources which don't confirm this/(my) info !


Dukaddy-DUKEs,
-Bob

[DewCatTea-Bob]

" I guess I'm willing to sacrifice the "science" for some fun. "

____ The science AND the fun can be coupled-together by running two Dukes & riders together ! _ And to extend the comparing-runs, be sure to put the heaviest-rider on the strongest motor.


" Not only that, but the serious experience I have available to me, I suspect most others dont have.
I'm not talking newbies here.
I'm happy I'll get some fair and balanced assessment from these guys - "

____ Impressive testers indeed to have at one's disposal ! _ So I must be excused for assuming that you most likely only knew of a few local fellow-riders who were (at least) comfortable with the right-hand shifting set-up on DUKEs, (if not ordinary Duke-owners).


" I'm going to take the approach of running stock first because I'm going to be messing with carb and ignition timing beforehand.I don't want the complication of an "odd" cam whilst I do that first. "

____ Oh, that's quite understandable then, (I had assumed all else was set to go). _ It is indeed best to go the route you're going then !
Just hope you can complete the cam-swap change-over within a week's time, so that the comparison-impressions can be more fair, (if without benefit of any 'control-sample' test-bike&rider).


" Yes. that was exactly my point. The comment about not being totally true to name was about a scramler club selling a desmo cam "

____ That's actually not so unexpected of course, (since it is a Ducati-part after-all),, but my-own main-point was that there's no "White" -(white only) DESMO-cam, (only White Scrambler-cams).
Perhaps there's a White-D.cam made for an L-twin ?


Dukaddy-DUKEs,
-Bob

[machten]

As I-myself seem to recall, the 750SS had it's very-own (streetable) D.cam-model, which was not as wild as the 'special' "Imola D.cam" which was based-on/inspired-by the ACTUAL (& nameless) pure-racing D.cam which had been employed during the original (& quite famous) Imola-race.

" The 73 Greenframe was homologated with the 1972 Imola cam. "

____ That's the first I've ever heard of that, as I believe that the special-order 'Imola-cam' had to be especially requested in order to obtain them ! - (At least for here in the USA.)

Here's my understanding...

The homologation of the 73 and 74 SS's are a matter of record. Falloon's research confirms this. How many of the 73 black case greem frames actually had the Imola race cams is a matter of debate. From memory there was circa 15 bikes all up and they were not generally available to anyone "off the street" at that time. It's not unreasonable to expect that they were directed at guys that were going to race production 750 and so came with the original 750 1972 imola cams on some such bikes.

The 74 Greenframe was available to anyone and did have the option of a the standard cam and so called "imola" cam. I doubt that was the same cam as the 72 or 73 short stroke race bikes (as you mention). But you certainly could buy a "race kit". It's in the ducati parts list and I've seen them. The 74 greenframes don't even start to come onto the cam before north of 4000 rpm (I' have a few owned by friends I occasionally get a squirt on). They are definitely more aggressive than Sports and GT's which are actually quite tame, by comparison. (EDIT: Having said that, a well tuned Sport doesn't lose much against a greenframe. I've never tried a Sport with 36mm dellortos, but with those and a little bit of porting....)

Going back to the main game...

After a sun up to past sundown effort, the 250 MK3D is now reassembled and ignition timed ready for a "fire up" in the morning with Marco's stock cam. Time for some testing!

P1011418.JPG

Kev