Motoscrubs.com

____ This new-thread has been started to prevent (at least) some of it's contents from becoming lost within another fairly unrelated thread.
Here's a link to that other thread from the post/point where the following DESMO discussion-topic first arose... viewtopic.php?f=3&t=1302&p=9446#p9428

DewcatTea-Bob wrote:By: Harvey...
" there was a cam that I got for a 450 desmo, Blue/Black "

____ I've heard-of a Blue&Black-camshaft for the 450 before but, I've never heard of a Blue&Black DESMO-cam,, are you sure that DESMO-cam wasn't actually 'Blue&White' ?

Harvey wrote:Well Bob it was 20 years ago , but the memory of that development is fairly clear, and I am going off the original correspondence that I had with Brook Henry at the time. It was always referred to as a Blue/Black cam, and I said 18*, one tooth out then, and have no reason to suspect that it was not.

This was over the space of three cams, the first was from Phil Hitchcock, that I suspect was a copy of an original cam. This cam was fitted to the timing marks and run. It was realised from the blowback that it was retarded. It was checked and found the 18* discrepancy. Retimed one tooth to run ok.

The second cam that Brook did for me had the same 18* problem,(that was probably still programed into the grinder), but also a phasing difference, in the inlet opening and closing lobes. So that the clearance changed from zero to 0.045" and back to zero through its travel. We corresponded and I sent all the valve gear to him, and we finally got the final V2 cam that was perfect.

What I was looking at mainly Bob, is that I have a good recollection that the first cam was a Spanish cam, that was copied. Phil may have a better recollection of where that cam was from, but reading of the Vento problem, it seemed to match up.

Graeme wrote:

", but also a phasing difference, in the inlet opening and closing lobes. So that the clearance changed from zero to 0.045" and back to zero through its travel"

I have found this on "some" Desmo cams but not all. And some worse than others, which I assumed was poor machining.
I've relieved, lapped, the closing lobes to achieve a constant clearance through the rotation.

Are you saying that the Spanish made Desmo cams and engines?
I wasn't aware they made Desmo engines?

____ Concerning the issue of DESMO-cams which happen to have their closing-lobes not-only machined inconsistently but also with a seemingly reckless varying max.lift radius which allows closed-clearance to waver (between 0 & up-over 1mm),
I have much to point-out on the matter ! ...
__ While it may seem to be a sad state-of-affairs that Ducati had allowed such apparently sloppy DESMO-cam machine-work to leave it's factory,, in their defense, PERFECTly-executed closing-lobes would've actually been an unnecessary added-expense which would've added no additional mechanical value to their desmo.product.
I certainly do-not disagree that it's extra-nice to have the closing-lobes absolutely perfectly radius-contoured for the closing-clearance to remain consistently under .01mm for nearly the entire duration of the closing-lobe, and I of-course somewhat admire and certainly commend those of us who actually care enough to bother with the extensive tedious-trouble of stoning-down their DESMO-cam's closing-lobes so as to attain such consistent closing-clearance perfection.
However, I-myself equate such extreme practice as being as usefully productive as something like adding pin-stripping to a paint-job on the insides of tool-boxes or the undersides of fenders, or the likes of placing DUCATI-decals onto the INsides of headlamps or fuel-tanks, etc,etc. ... It's a pretty NICE-touch but, is it really worth it ? - I believe NOT !
____ I recall back when our local Ducati-shop received their very-first DESMO-model -(a 1968 '250Mark3D'),, both the shop-owner & the Norton-mechanic had realized what the included DESMO valve-train was supposed to accomplish, (and of-course I as well had read fairly recent mag.articles about Ducati's new desmo.engines), but back-then, of-course nobody had any idea of exactly what the innards of a DESMO-head actually looked like. _ And the shop-owner would-not agree to let anyone attempt to have a look-see at the inside of the Mk3D's cyl.head, (as he didn't wish to chance messing-up anything before it was sold).
So later one-day when the shop-owner was out of town, Dave -(the Norton-mechanic) & myself dared to investigate & take a peek at the inside, to hopefully satisfy our curiosity (about what Ducati had changed inside their cyl.head without any significant exterior alterations).
When we finally managed to get the DESMO-cover (very carefully !) off the head, Dave looked-in first & seemed disappointed that there was next to nothing he could easily see in-behind inside there,, so I next looked-in and was unexpectedly SURPRISED to see such an overly-LARGE cam-lobe (with about 5 holes through it), and I didn't immediately understand what was what inside there. _ But before getting a good-grasp of the unexpected concept, I had to hurry & get it back-together before the boss might get back some-time soon that day. _ (We never mentioned to the boss what we had done, until some time after the Duke's warranty-period had expired.)
The reason I was so surprised (about the design-shape of the DESMO-cam) is because, I, (like the author of the related mag.article I'd read), only knew of what the DESMO-head was supposed to be able to accomplish with the valves, but actually knew of nothing to do with the actual working-mechanics of that desmo.process (designed by Ducati).
So I had only imagined an extra pair of rockers with two extra cam-lobes, with the particular rocker-design being left unimagined and the extra/(closing) cam-lobes being imagined as being little different (duration-wise) from the regular opening-lobes, (as I had envisioned such ordinary type cam-lobes as quite sufficient for the closing-job), thus my confused-surprise at first seeing such an abnormally-extended duration cam-lobe.
__ The reason I had assumed that the closing-lobes would-not be so greatly different-APPEARING than ordinary cam-lobes, is because I had read in the mag.article that while Ducati was still going to employ valve-springs in their production DESMO-models (ONLY for the sake of starting-purposes), their racing DESMO-engines however had not required valve-springs because (for racing-machines) once the closing-lobe performed it's intended purpose, the induced 'momentum' would then be what actually closes-shut the valves for the final-remaining clearance-space -(under 1mm), the rest of the way onto the valve-seat, and then internal cylinder-pressures would take-over & keep the valves held-closed (until the pressure next becomes released when the valves are once-again opened [by the opening cam-lobes]).
__ So-thus it now ought to be understood that having the closing cam-lobes held-responsible for also HOLDING the valves kept-shut, is not really a significant concern, ESPECIALLY when there are (even rather WEAK) valve-springs included (rather acting as a '2nd.string' behind the valve-seating effect of positive cylinder-pressure) !
__ So-sorry to point-out to you fellas who have gone-ahead & bothered yourselves to perform the extra-taskful closing-lobe manicure-detailing, but once the valve has been pushed-closed by the closing-cam's lobe-ramp & initial-peak, then the majority of the REST* of Ducati's extended closing-lobe area (* see pic) is rather useless and may-as-well be completely ground-away (as pure dead-weight) !
____ Now I realize that I'm no-doubt ruffling some of the feathers in the caps of those of you who are DESMO-nuts, and that most of the DESMO-worshipers just simply won't believe what I've just claimed,, but for those of you who are smart enough to, think-it-out for yourself and you'll then realize that ya should've already realized all of this good-reasoning, for yourself. --- Just think, (and then realize it).
__ Any arguments ?


Dukaddy-DUKEs,
-Bob

I would think the cam blank would have been machined, key way and thread fairly close if not exact, then the lobes close but oversize then hardened, then the lobes and bearing shafts would be finish ground to spec.
Assuming the key way was the setting point to machine and grind, the cam must not have been set correctly (exactly) where it should have been?

I have seen .3mm out on one closing lobe and slightly more on the other (on the same cam) and some not so bad. I haven't seen a close to perfect Desmo cam, but I've only played with half a dozen or so.

1mm out wouldn't surprise me, but that is a major problem and would do nasty things to the lobes and rockers if shimmed and not checked.

Graeme

My experiences reflect Graemes. I've seen just one well phased opener/closer lobe machining on a Blue White camshaft out of the four I've dialled - and two of them were unused. You can see more about my desmo cam experiences here...

http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=459&hilit=wc+oil+pump&start=10

Kev

graeme wrote:I would think the cam blank would have been machined, key way and thread fairly close if not exact, then the lobes close but oversize then hardened, then the lobes and bearing shafts would be finish ground to spec.
Assuming the key way was the setting point to machine and grind, the cam must not have been set correctly (exactly) where it should have been?

I have seen .3mm out on one closing lobe and slightly more on the other (on the same cam) and some not so bad. I haven't seen a close to perfect Desmo cam, but I've only played with half a dozen or so.

1mm out wouldn't surprise me, but that is a major problem and would do nasty things to the lobes and rockers if shimmed and not checked.

Graeme

____ Graeme, your post-wording seems a little out of place without also 'quoting' whatever particular posted-wording had inspired your stated comments.
As I, for one (without such guidance), am thusly left a little-bit lost.
____ What can possibly be done (if you wish), is to open 'Wordpad' and then highlight the intended wording from whatever post, and drag it over-to your wordpad-page, then-next you can again drag & drop it from wordpad into your-own post.
__ Hope this is helpful. _ (As that is the process I used to copy-over the posts from the other thread.)


Cheery-Cheers,
-Bob

Bob, my post wording regarding how I expect a cam is manufactured is to do with the posts of key ways being 17* out etc.

You lengthy post regarding Desmo cam tolerance and suggesting that up to 1mm of wrongly ground closing lobe is of no significance is not correct in the cams I have worked with.
Because the incorrectly shaped closing lobes would close the gap set on the opening shim at the point where the valve would start to open and also where the valve was almost closed.
So to have a cam closing lobe that was 1mm out, to use your dimension, would require the opening shim clearance to be at least 1mm to prevent the opening and closing rockers from binding and damaging the cam lobes or the rockers at the point where the valve is just starting to open or is almost closed.
This is what I have personally seen, and spent the considerable time lapping those points on the closing lobe to allow the opening shim clearance to be set. And maintained throughout 360 degrees rotation.
I have no doubt that the cylinder pressure will close the valves, I have a friend who has his closing shims sloppy so he can easily kick his 450, and it runs ok.
But the point of spending time playing with cams is not to get the closing lobes to correctly close the valve but to allow the opening clearance to be set.

(I'm typing this on a iPhone so I can't copy and post previous posts and forgive me if this thing has changed some words it thinks I have wrong that I have missed correcting)

Now on a pc, and editing what I have written,,,,

If the closing rocker is shimmed at 0 clearance "without springs" and rotated through 360 degrees I have found there is no problem.
Then each opening rocker is installed and shimmed to whatever you want (I'm not going into the gap clearance you prefer) at tdc compression, then roll the engine through and see the opening clearance disapear and become a negative clearance.
Does this make sense?

The point I have found where the interferance is, is at the point on the closing lobe either end of the "flat" where the valve is just opening or almost closed. And sometimes up to 10mm along the flat of the closing lobe away from the edge of the circle.
I have never seen the opening shim clearence open up, only close up.

Graeme

" Bob, my post wording regarding how I expect a cam is manufactured is to do with the posts of key ways being 17* out etc. "

____ I had gathered that but, I would've found it helpful to have been pre-orientated as to exactly what you were specifically meaning to address, so that I wouldn't have to try to figure that out while reading-through. _ Cuz it didn't seem to obviously pick-up from where you had left-off, in a seamless manor.



" You lengthy post regarding Desmo cam tolerance and suggesting that up to 1mm of wrongly ground closing lobe is of no significance is not correct in the cams I have worked with. "

____ I'm now suspecting that you've never read-through the older thread which has fairly thoroughly covered such issues ? - viewtopic.php?f=3&t=459&p=3588#p3588
__ Were any of the (supposedly) malfunked-up DESMO-cams which YOU "have worked with" taken from stock/running DESMO-engines ? _ Or were they all aftermarket, never before used examples ?



" Because the incorrectly shaped closing lobes would close the gap set on the opening shim at the point where the valve would start to open and also where the valve was almost closed. "

____ That fairly common issue has been most often referred-to as "binding", - those rotation-points where the opening-rocker & closing-rocker are fighting for the same bit of space (because the high-points [disconcertingly left mis-machined] on the closing-lobe haven't been kept shaved-down perfectly in-concert with the opening-lobe).
__ That neg.clearance issue is of-course more apt to occur when the closing-clearance is set to spec BEFORE the opening-clearance is set.
But still however, that binding-occurrence of-course remains apt to come into play IF ya maintain the mind-set that the ENTIRE closing-lobe's track-face must ACTUALLY serve what APPEARS to be it's intended function. _ And while that (actually un-useful) function may have ORIGINALLY been intended to actually fulfill it's apparent function,, in (later-day) actuality, that (seemingly useful) function can't actually come into play, (unless ya go-ahead & perform the work of shaving-away the high-spots from the closing-lobe).



" So to have a cam closing lobe that was 1mm out, to use your dimension, would require the opening shim clearance to be at least 1mm to prevent the opening and closing rockers from binding and damaging the cam lobes or the rockers at the point where the valve is just starting to open or is almost closed. "

____ That's of-course quite true when the clearance-adjustment is not properly compensated for such, (ESPECIALLY when the closing-clearance is set BEFORE the opening-clearance setting is begun) ! _ (And there have been found such opposing-fights for the same space even greater than 1mm-deep overlap [past tangent] !)
__ This rocker-clearance fighting-issue over the same space (at those two commonly discovered locations), is not just due to the (fairly well known-of) undesirable machine-work on the closing-lobe, alone,, but rather more-so due to the mind-set of those who believe that they understand the (rather fake)- purpose of the closing-lobe's EXTENDED duration ! ...
__ So as to completely avoid any such binding-issues, the opening-clearance has to be set to spec FIRST (while at TDC, of-course),, then-next, the closing-clearance is set to spec -(0 to .05mm), but NOT at TDC ! _ RATHER, the closing-clearance (on an unmodified D.camshaft) MUST be set to compensate for WHERE-EVER it's discovered that the closing-lobe has it's greatest degree of opposing interference, (as IT's resulting clearance-amount is relatively insignificant !). _ And yes that means that the closing-clearance may even be over 1mm at TDC ! - But that's OKAY, so long as the closing-clearance has been set loosely enough so that there's no such negative-clearance fighting occurring ANYWHERE around the 360-turn of the camshaft). _ And if that happens to mean that the closing-clearance can't possibly be set to spec, then it really doesn't matter anyhow ! _ So ya just live with it as it has ended-up, (which hurts nothing other than ya'r mind-set), or-else ya have to waste a bunch of time stoning the high-points off-of your closing-lobes (merely to appease ya'r mind-set).
__ So yes, this all means that with such a sloppy/undetailed commonly-stock DESMO-cam, the VAST-majority of it's closing-lobe's track-face is left virtually FUNCTIONLESS !
And-so since there may be a millimeter or-so of clearance-SLOP between the greater-majority of the closing-lobe's track-face & it's cam-follower, you now thus ought-to realize why I've declared that the VAST-majority of the closing-lobe may as well not even exist.



" This is what I have personally seen, "

____ Of-course not just yourself, but pretty-much all-other perfectionist-types have noted-of as well.



" and spent the considerable time lapping those points on the closing lobe to allow the opening shim clearance to be set. And maintained throughout 360 degrees rotation. "

____ Yes that then sure makes the closing-lobes become pretty-much 100% consistent and nicely-pleasing to one's mind-set desire for nice & cleanly concerted-organization.
__ However it seems somewhat apparent (to me at-least), that Ducati ORIGINALLY had the same mind-set for such concerted-perfection,, but soon thereafter originally-designing their particular closing-lobe architecture, then came to realize that the perfection doesn't really matter, and-so thus-then allowed their manufacturing-process to become so rather sloppy, as the later DESMO-cams came to be done.



" I have no doubt that the cylinder pressure will close the valves, "

____ Right, and any valve-spring (if present) would of-course work in concert to that end,, thus leaving the ONLY functional-purpose for the closing-lobe's entire extended track-face, to be merely-JUST that of it's 'closing-RAMP' ! _ Solely just to make-SURE that it's controlled valve isn't left-behind (the opening-cam's intended valve-timing). _ So THUSLY therefore, the REST of the (partially fake) function of the closing-lobe's track-face, is overtly 'REDUNDANT', and-thus unneeded !!
And that's no-doubt got to be the reason for why Ducati had gone-ahead & left the closing-lobe to be so sloppily machined ! _ And yet, having been remained-left completely intact, means that the unnecessary-area of the closing-lobe track-face length, now only serves just a "FAKE" function ! - (That [worthless!]- function basically being merely to fool ya into assuming that it still serves some useful function, [which it actually can no-longer perform,(if not modified for perfection)].)



" I have a friend who has his closing shims sloppy so he can easily kick his 450, and it runs ok. "

____ SEEMS that he has realized that seemingly excessive closing-clearance slop is of no real concern, (as valve-mass momentum will finish-up that which the closing-lobe leaves unfinished).



" But the point of spending time playing with cams is not to get the closing lobes to correctly close the valve but to allow the opening clearance to be set. "

____ This brings us back as to whether YOUR DESMO-cams were produced by Ducati or not,, as those two concerning aspects -(valve pulled-closed fully to it's seat [albeit only for just a BRIEF-moment of the entire closing track-face], AND without interference with opening-clearance std.specs), usually go hand & hand,, as solving one aspect usually also serves to solve the other as well.
__ Because of the machined closing-lobe deficiency, the closing-clearance may have to be set further outside of the ORIGINALLY-designated clearance-spec, (but not by any excessive amount which could possibly make any functional difference).



" If the closing rocker is shimmed at 0 clearance "without springs" and rotated through 360 degrees I have found there is no problem. "

____ Indeed that's usually how it is, as the negative binding situation is-NOT really due to the closing-lobe's radius actually having "high-points" which protrude relative to it's OWN-SELF, but rather merely lobe-points which happen to be too-high in regards to being accordingly-matched with one or two areas of the architecture of the opening-lobe.
And since the opening-lobe HAS to be that which it is, then it's the CLOSING-lobe which must have to be considered as being THE lobe that's really at fault (even-though it-itself may seem to be perfectly pleased with ITSELF).
__ So the "high-points" really aren't 'higher', rather they are just-merely the disconcerting inconsistent-points which can possibly lead to binding conditions, if not properly dealt with (one way or another).



" Then each opening rocker is installed and shimmed to whatever you want (I'm not going into the gap clearance you prefer) at tdc compression, then roll the engine through and see the opening clearance disapear and become a negative clearance.
Does this make sense? "

____ Yes, assuming that you mean "negative clearance" in regards to that which the set closing-lobe clearance is allowing for.
However that negative-clearance issue is apt to arise since two aspect-points are (possibly improperly) left unaddressed...
Firstly, the opening-clearance must be set FIRST, because it's all that's really important,, and secondly, the closing-clearance is not necessarily to be set at TDC (as may seem ought to be done), but rather set for maximum-closure ALLOWED-for (for appeasing whatever rotation-point that would otherwise lead to any such negative-clearance opposition). _ And if that resulting-clearance happens to be up to a millimeter (or so) out of preferred spec, well-then that's really no significant issue actually. _ As the closing-clearance actually has no important reason to be set right-at "zer0" (even at ANY rotation-point) !
The main-function of the DESMO closing-lobe -(it's closing-ramp) will still perform it's (rather important) intended-job equally well regardless of how loose the closing-rockers are set ! _ (It's merely-just NICE to have them be set to original factory-spec & running [somewhat quieter] that way.)



" The point I have found where the interferance is, is at the point on the closing lobe either end of the "flat" where the valve is just opening or almost closed. And sometimes up to 10mm along the flat of the closing lobe away from the edge of the circle. "

____ I believe that's about par-for-the-course for later-production DESMO-cams,, but the interference you encounter must depend on a couple of unmentioned points... One, where do YOU set your closing-clearance at, TDC ? _ And two, do you insist on setting that clearance right-at '0.0mm' ? - (Which really isn't necessary !)
__ Anyhow,, whichever interference/binding area-spot provokes the GREATEST negative-clearance binding-interference, is the particular point where your closing-clearance shim-retainer must be shimmed for the "0" spec - (for the space between the retainer & that which the opening-rocker will happen to allow, [and not necessarily for between the closing-rocker & closing-lobe). _ In other words,, there's really no logical-sense in being concerned with whatever the amount of closing-clearance happens to be between the closing-rocker & closing-lobe (at TDC),, but RATHER-instead, it's only the closing-clearance that's between the upper & lower rockers that's ACTUALLY important, and THAT'S the clearance-point which NEEDS to be properly adjusted (for at-least 0-clearance) !
And if that happens to result with as much as a millimeter of closing-clearance slop at TDC, well then (as I've explained), it doesn't really matter anyway. _ (Thus that's why I contend that that (virtually useless) section of the closing-lobe may as well be eliminated [as useless dead-weight].)



" I have never seen the opening shim clearence open up, only close up. "

____ Of-course that's to be expected,, as as unlike the closing side, the opening side rides on the (smaller radius) base-circle of the shaft, (rather than on the [larger radius] closing-lobe track-ridge), thus meaning that when moving-away from TDC.position, the opening side becomes lifted-UP ON-to a lobe, whilst the closing side falls-DOWN OFF-of a lobe.



UPDATE - I've had some time to read-over & edit much of my previous post-wording above, and-so have now corrected some previous poor wording. _ And however, I've also added a good bit more (which had been inadvertently left-out before), so I've still done a fair bit of off-the-top-of-the-head post-wording here-above,, so if anyone comes-across any wording that ya have ANY trouble comprehending, then please 'quote' it, and I'll then see about rewording it in a different light/angle.


Dukaddy_DUKEs,
DCT-Bob

After looking at some more papers and notes that I wrote around that time, (1992) I can now fill in the process of the three cams that lead to the V2 cam.
I had been looking for a 12mm lift cam for my modified 450 for some time, had tried all the cams that Phil had, when he told me that there was some being made by Brook Henry, so I put me on the top of the list.
As soon as it was done, I fitted the cam (that was referred to as the Black/Blue), and found that the keyway was one tooth out, and the inlet lobe was about 6* advanced to the closing lobe. The result was that the clearance would change from zero to 0.045” over the opening phase.
This is the clearance figures for every 20* of Inlet rotation.
Degrees rotation……………..Tappet clearance.
0………………………………0.007”
20……………………………..0.002”
40……………………………..0.000”
60……………………………..0.000”
80……………………………..0.007”
100……………………………0.018”
120……………………………0.025”
140……………………………0.032”
160……………………………0.014”
180……………………………0.043”
200……………………………0.045”
220……………………………0.045”
240……………………………0.041”
260……………………………0.037”
280……………………………0.033”
300……………………………0.029”
320……………………………0.016”
340……………………………0.007”

Needing to press this cam into action, the opening lobe was stoned to reduce the clearance to 0.024”, and the cam advanced one tooth. I told Phil of the problem as he was going to send some of them out to others. I used that cam like this, till a better one could be made, but always had a fear of the half rings dropping out.
But it was not the cam that I wanted, as the duration was too long, better suited to a 250. I asked Brook for a cam that was the same as the cam in my 76 750SS,

So the second cam arrived, although it had the duration and lift that I wanted, it still had the same key and phasing faults as above, that seemed to still be programmed into the grinder. As these cams were the first single cams that V2 made, I sent all the valve gear over to him, to fit to a head and fix the problem.

The third cam arrived and was perfect, keyway fixed and the phasing was as smooth as silk, and from the first start, the crack of the exhaust sound, told me I had found the right one. The cam had no markings, but was coded in the “slowly disappearing photocopy of the time” to be lobes V2030, and V2032. the rest of the specifications are the same as the copy that Machten posted on his 250 thread. The head only had a rocker spring on the exhaust closer, to help kick starting.

In Kev’s thread he said that the cam fitted into the 250 head without any machining, but the cam I got had to have the tunnel bored out about 3/4mm? and a sleeve fitted to the cam cover, to center the bearing, as can be seen here.


All in all it was a successful process, as the cam suited the engine, to make the ‘450SS’ that should have been made.

" As soon as it was done, I fitted the cam (that was referred to as the Black/Blue), and found that the keyway was one tooth out, and the inlet lobe was about 6* advanced to the closing lobe. "

____ Well then I guess that may be the reason for why I had never heard of a 'Black&Blue' 450-DESMO-cam... your DESMO-cam.model wasn't actually produced by the Ducati-factory itself.



" the cam I got had to have the tunnel bored out about 3/4mm? and a sleeve fitted to the cam cover, to center the bearing, "

____ Usually, (providing that the cam.tunnel was exactly center-bored), such a support-sleeve is-not really needed specifically just for that centering-purpose merely-alone, (as the 4 retaining-screws still keep the support/cover centered in the same place),, but rather mainly to make-sure that the oil-passageway is maintained (to prevent massive-leakage between the tunnel-wall & camshaft bearing-support/cover),, and-also retain snug-fitment for maintaining support for the nose-end of the cover.



" to make the ‘450SS’ that should have been made. "

____ I agree, as I've also imagined such a 450-model,, however (back in the late '70s) I envisioned a 450SS with it having the top-end of a 900SS !
__ I once mentioned that conception to a fellow back in 2007, and he informed me that some fellow in Holland/(Netherlands?) had already managed to modify a 450 bottom-end to successfully adapt a 900L-twin top-end to it.
I was of-course surprised & delighted to learn that my idea had already been thought-of & executed as well ! _ But I've unfortunately never heard any further tale of it since.
Sure would be nice if someone of us here could confirm such a wonderous tale and perhaps also provide a lead to help locate it's whereabouts.
Of-course I've since had doubts of it's actual existence however, cuz it seems that if such a modified 450-Duke motor really existed, then I'd expect that Eldert would've mentioned something about it before now.


Hopeful-Cheers,
-Bob

" Usually? I wouldn't leave that sort of support to luck Bob, Murphey's law rules. . "

____ I had stated "Usually", only because most bored-out tunnels get machined without centering-errors.
Besides, I don't think any luck is really needed to help keep the 4 original screw-holes kept in their place.



" Yes I have heard of the 450 with the 900 head, get a better inlet port direction. "

____ Not to mention a cyl.head which can handle a 40mm intake-port & carb !


Dukaddy-DUKEs,
-Bob