450 Mark 3 Camshaft Change

[DewCatTea-Bob]

____ Sorry for the delay with this, but when my internet-connection happened to be working, I then wasn't yet in the mood to come-back and redeal with this stuff.


[quote= Bevel bob ...
" Thank's for clearing that up Bob, "

____ I had only begun to do so ! _ The other 2/3rds of the intended response-wording would've included significantly more related info, IF THAT PART HADN'T GOTTEN LOST !
__ I still have yet to completely get-over that lost (and the associated feelings !), but still expect to go-back and try to refinish that lost work, later.



" Does this cam cause reversion , blowback "

____ The F1/G&W.cam-version's wild timing will tend to do so in a 250 more-so than in larger engines but, I wouldn't say that ought-to be expected unless the muffler is too restrictive. _ As that cam.model was (originally) expected to be run in combo with an open megaphone-exhaust (on a mere 250cc.motor... ).
__ At low RPM with such a wild cam, the small volume of a 250-cylinder is rather easily filled and the relatively slow/weak velocity/momentum of the intake-charge thusly becomes insufficient to further overwhelm the building pressure within the cylinder as the piston rises towards TDC whilst the intake-valve is still left held-open (due-to valve-timing best suited just for high-RPM), and-so the in.valve fails to contain the entire intake-charge ! _ So it shouldn't be unexpected for some "blowback" to occur, during low-RPM !
__ However in the case of the 450,, the ratio of it's increased intake-charge momentum/velocity vs. a relatively unsatisfied cylinder-volume (only having a built pressure that's possibly still-not as great as the atmosphere-pressure), will much less likely suffer with any such reverse-flow (back-into the in.port at low-RPM). _ So that's partly why a cam that's considered to be very-WILD for a 250, is-not actually so wild within a 450 !



" and richness in your experience, "

____ I'd say no to that, (overall, RPM-wise). _ However during low-RPM (when in.port charge velocity is then rather low),, if you have a long inlet-duct/tract outboard of the carb, THEN you may possibly get a bit of 'double-carburetion' (as the drawn-in fuel-mix is pushed back-out & through the carb and then sucked back-in AGAIN), which of-course causes an extra-rich fuel-mixture, (but just at low RPM).
____ As for my-own "experience" with the F1-type G&W.cam in a '250',, I regret to admit that I really don't have any practical personal-experience, other than the following stuff...
__ I have a w-c.250 engine-project (with NOS Mk.3-head & F1 valve-springs), which includes my very-first intention to employ a 250F1-cam within a mere 250-engine. _ But unfortunately, I never got-around to completing the motor-build so I could 'experience' the results of that project-build !
__ However I have installed a 350Mk.3/G&W.cam in a n-c.250-M1 cyl.head, and that 250-engine ran quite well enough without any notable issues, (although it wasn't ever tried-out with a SSI-carb, [just a 30mm-Amal] ) !
__ Of somewhat rather closely related interest however, I have the following tale to tell...
Back in 1980, I met a young-fellow who's brother had once installed a new ring-set on a 1965 n-c.250-Scrambler, but wrongly-installed a new cyl.base-gasket which blocked-off the oil-way and-thus caused the cam & rockers to become destroyed !
So he brought his cyl.head to me along-with another head taken from his brother's wrecked 1970 350-Scrambler, (so I could replace the original/destroyed parts for him).
But he had simply assumed that the 350's cam was just another 'scrambler-cam', and it was-not very easy for me to convince him that 350-Scrambler cams were actually racing-cams and-so he'd also need the 350-head's stronger ex.valve-springs to suit.
After swapping-over the 350-Scr camshaft & rockers AND-also ex.valve-springs, to his 250-Scr.head,, he later told me that his 250-Scrambler ran quite well enough (after he installed the carb from the 350-Scrambler as well).
He may not have experienced the very-same running-issues as yourself, since his 250-Scr.intake-port (& in.valve) is smaller than that of your Mach-I cyl.head, (plus he ran with a stock n-c.Scr open-ex.pipe !).
__ That's pretty-much all the previous-knowledge I-myself have concerning G&W.cams for 250-engines.



" or have i just got the wrong combination of carb or exhaust?. "

____ Your 250 has a 27mm-SSI, I think,, doesn't it ?
__ If you're running a muffler with any kind of internal 'baffling',, then try running rather with a straight-through ex.pipe-extension or 'shorty' glass-pack silencer, and-see if your particular troubles at-least become reduced.
But rather than either of those two suspects, your camshaft's timing is rather suspected.



____ I still expect to add extra wording to my previous post (on page-1),
so ya might care to check-back later to find additional info of related interest, (such-as like I've now done on THIS-post).


Duke-Cheers,
DCT-Bob

[Bevel bob]

Thanks DCT-bob. I will try a straight through exhaust with absorption design, a megga is just too anti-social .I'm running a 29 mm SSi with the long v/stack, The carb is not helping and the 27mm would most likely improve the low speed range.Trying to tune out the reversion richness with weaker carb settings is a fruitless exercise as I think it ruins the mixture at other revs.A cam change is the best solution ,so if someone is up for a swap?. I need a Mach 1 ,Mark 3 , Dianna cam or the less wild green white, Narrow case .I think my cam would be good for a race rep 250/350 or a 450 cafe ,

[DewCatTea-Bob]

[quote= Bevel bob ...
" I will try a straight through exhaust with absorption design, "

____ Let us know what you find & consider for replacing whatever is your current muffler. _ And if it's something expensive,, then you may first care to simply try running without your muffler, to determine if your muffler actually contributes to your running-issue.
__ The reason there's some hope that replacing your muffler may directly address your running-issues, is because when an overly wild cam is matched-up in combo with an overly restrictive muffler, THEN two mal-actions occur ! ...
(Keep in-mind that an overly wild 'wild-cam' [such-as the 250F1-cam], is a cam that opens valves extra-early and-also closes them extra-late.)
The "mal-action" begins with the muffler's undesirable restriction of unimpeded air-flow, so-thus the wild-cam's intention of taking full-advantage of exhaust-air momentum/velocity to suck-out spent-gas from the cyl.chamber (by keeping the ex.valve held open well past TDC), is not-only much curtailed (by 'back-pressure'), but also exhaust-pressure (on either side of the ex.valve) then can't get completely reduced down-to normal atmospheric-pressure,, so that causes some ex.gas to get pushed-out past the intake-valve also, (since the in.valve was opened too soon by the wild cam).
Next, since the intake-charge has to enter into a cylinder which is less than fully emptied-out, the intake-charge then has to be entirely PULLED-in (without the regular-assistance of the otherwise expected 'ram-effect' of intake-charge momentum/velocity). _ And with that rather early-built cyl.pressure being further increased as the piston pushes towards TDC, then some of the intended fuel-charge inevitably rather gets pushed-out past the in.valve (since it's held-open too late).
__ So it now ought-to be understood how a restrictive muffler is able to much exaggerate the disadvantages of a wild cam at low-RPM, (and also fairly-well curtail the expected advantages of a wild cam even at high-RPM, as well) !



" I'm running a 29 mm SSi with the long v/stack, "

____ Have you ever tried running without the v.stack (to see if it has any relief effect on your rich low-speed fuel-mix) ?



" The carb is not helping and the 27mm would most likely improve the low speed range. "

____ If you care more about reliable function rather than 'looks', then I'd suggest you get yourself a 27mmVHB/square-slide from a w-c.250Scr or a 350-Sprint.
__ Have you ever tried ANY other carb so as to confirm that your rich-mix is actually due-to your installed wild-cam ?



" Trying to tune out the reversion richness with weaker carb settings is a fruitless exercise as I think it ruins the mixture at other revs "

____ If you could be successful at adequately canceling your low-speed richness, then so long as your higher-speed spark-plug readings don't get too light-colored, your leaner-mix might be okay.



" I need a Mach 1 ,Mark 3 , Dianna cam or the less wild green white, "

____ The difference between the two G&W.cam-models is-not really worth the trouble of swapping them, for your particular purpose. _ And the Diana250-cam is the SAME rather mild cam as stock in any n-c.250-Monza !
__ Perhaps you may consider asking Eldert if he'd possibly accept your cam as partial-payment towards one of the special-grind units which he's having manufactured.
____ Also, you may wish to try contacting fellow-member/David, to discuss such related matters.
Here follows a link to his related thread-post... viewtopic.php?f=3&t=1335&p=9147#p9144


Hopeful-Cheers,
DCT-Bob

[Eldert]

it took a lttle while but the camshafts are ready .



Eldert

a camshaft maker is making me some cams with the Mach 1 grey cams timing and a little more lift ( 11 mm intake and 10 mm exhaust ) for my 500 RT playbike . let see how that works out .

Eldert

[ducwiz]

http://www.ducatimeccanica.com/JimsCamData.pdf may give some more information.

cheers

[DewCatTea-Bob]

[quote= Eldert ...
" it took a lttle while but the camshafts are ready . "

____ Thanks for the long-anticipated update Eldert ! _ I had foreboding concerns that your order may never have become completed. _ And that would've been a certain shame,, cuz surely for one-thing alone, that's quite a pretty model for a Duker-eye to be allowed to behold a gaze upon !
How about also providing us with a pic.shot of your cam's 'profile' (as squarely viewed from it's left-end/side), so we can then see how impressive it actually is ?
__ Hopefully you've acquired sufficient quantity to somehow become coaxed to part-ways with at-least an example or two for others of us to also reap advantage of ! _ Care to quote a price that could accomplish such a golden-exchange ?



" a camshaft maker is making me some cams with the Mach 1 grey cams timing "

____ I must praise you Eldert for your good-sense of prudent-restraint by not jumping-onto-the-bandwagon with all those who'd rather choose to push-the-envelope and have the maker create further extravagant cams with overly wild valve timing probably exceeding even that of the std.DESMO/250F1-cam.models. _ Although while I'd still suspect that your smartly restrained cam-design's timing-specs may accordingly forfeit a significant-fraction of an HP above 8500-RPM,, I'm quite sure that small loss will be significantly-more than compensated for within the low & mid rev.ranges, thus making your 450 a much greater treat to ride !
It's kinda too-bad that all examples you've had made for you had to have the same Gray-cam.model timing-specs -(62bt - 76ab / 70bb - 48at), cuz while that's plenty wild enough for 250/350-engines, the duration-times are a bit on the mild-side for 450/500-engines. _ So if your 450/500 runs with an exhaust-system which has any back-pressure, then it'd be better if the exhaust-timing were closer to the Mark-III's -(75bb - 55at).
However I'd be pleasantly-surprised if the camshaft-maker you happened to find & employ to make your camshafts, actually got the cam-timing properly set within 1-degree of the requested specs ! _ So hopefully, (for mating with 450-engines anyhow),, any slop-tolerance that might've gotten included, will happen to be off-target towards the timing-specs* of the 350Mark-3 cam.model -(* 65bt - 76ab / 80bb - 50at).
__ If it turns-out that you're not fully pleased with your 500's high-end performance with the Gray-timing, then I'd recommend that your next batch of ordered cams have timing-specs closer to: 65bt - 80ab / 80bb - 60at (but not any wilder).



" and a little more lift ( 11 mm intake and 10 mm exhaust ) "

____ That's quite a significant increase in lift over the Gray/Mach-1 cam.model's 9mm & 8.5mm lobe-heights, (yet without going overboard to an overly excessive extent),, and should especially benefit the 450-capacity !
However for the higher revving 250-engine, I'm inclined to suspect that the regular ex.valve-spring may become strained to continue keeping 'float' totally nonexistent. _ (Of-course valve-float on the intake side is-not as much of a concern, since it's not possible for the intake-valve to be left in the way of the piston.)



" let see how that works out . "

____ Your update-post has gotten me so excited that I can't-wait to get your report on how well such cams improve your 450/500-engine's power-delivery ! _ I expect it to be pretty-much the best for overall power-production across the entire rev.range !
__ Certainly you don't have anything else that would be a better use of your time than getting one of your new cams installed into your 450/500 !
But before you do,, you should first compare the acceleration of your Duke against some fairly-well matched bike & rider, so that you'll then be better able to gauge the improvement you'll end-up with.


Hopeful-Cheers,
-Bob

[Eldert]

i have this poor picture of the cam's lobes on my computer


this cam is made for my motocross project . i am a novice motocrosser and wanted a engine with lots of bottompower and midrange grunt .
for interested people that are on Facebook i have a page about the build

the build of a 450/500 cc Ducati motocrosser

lots of interesting stuf

Eldert

[DewCatTea-Bob]

[quote= Eldert ...
" i have this poor picture of the cam's lobes "

____ Well I'm afraid I can't disagree with you about the quality of that pic.shot Eldert. _ Perhaps some other time you could give us a better lite-up view of the lobes as seen from the shorter left-end of the shaft.
__ It appears that the passage-hole in the shaft's right-end was left totally closed-off by the maker, or have you-yourself blocked-up that hole with some kind of plug ?
__ Have you yet checked to make-sure that your camshaft order actually met all the cam-specs which you had requested the maker to fulfill ? _ (I've never found an aftermarket camshaft-maker who's end-product exactly met the expected cam-specs as promised !)



" this cam is made for my motocross project . "

____ OHH ! _ I had assumed that your "500 RT playbike" was also a road-going machine that would be primarily used for fun road-riding, and-so wanted to replace the stock Scrambler-cam with a cam perfectly suitable for such use.
I really wasn't expecting you to be doing motocross-type riding with it.



" i wanted a engine with lots of bottompower and midrange grunt . "

____ Well then for optimum power-delivery for motocross-type riding, I'd say you've likely hit the nail on the head with the Gray-cam valve-timing within a near-500cc engine intended for such riding-conditions where you'd likely never get an extended chance to wind-out the engine near top-RPM !
__ For best low-end 'grunt', the Gray-cam's valve-timing would certainly be a bit too wild for the std.435cc-engine,, however with a greater capacity near-around 490cc, that Gray-timing is more tame and likely will thusly become mild enough to provide pretty-decent low-end grunt to serve your low-speed motocross-riding situations quite well enough.
Where I believe your chosen M1/Gray cam-timing will really hit the mark at, is in the mid-range -(4 ~ 7 grand) ! ...
It's my opinion that you probably couldn't tweak the Gray-cam's timing-specs any at all to get any noticeably better power-delivery from a 500cc-engine near-around 5500-RPM (+/- 1-grand). _ So it seems to me that you've done your homework well, before placing your camshaft-order ! _ As I expect that Gray-timing will provide a good power-spread between 4k ~ 7k RPM with your 500-playbike !
__ So anyhow, since your 500-playbike project is intended for 'motocross' riding and not for spirited road-riding,, that then of-course means that the timing-spec tweaking which I had previously suggested, is no-longer valid (as I now realize that you've got it RIGHT, Eldert !).



" on Facebook i have a page about the build
of a 450/500 cc Ducati motocrosser "

____ Couldn't you have included a link directly-to ?



" lots of interesting stuf "

____ Of that, there can be no doubt, Eldert !




____ Well it seems I've been left to assume that you didn't have enough of those high-lift M1/Gray-type camshafts made so as to be able to spare any for selling to anyone else.
If so, that would be fairly disappointing, cuz that high-lift M1.Gray-cam would be great for a std.450 and absolutely fantastic for any 350 road-rider !
__ So if there's anyone else of us who'd also like to have such a camshaft made, what can you tell us to expect ? ... Is there any minimum-order, and what kind of pricing does your found camshaft-maker charge ? _ And could there be any other unforeseen road-blocks any of the rest of us might have-to hurtle in order to successfully procure a completed deal with that cam-maker you've dealt with, (such-as possibly needing to provide used camshaft-cores) ?


Excited-Cheers,
-Bob

[Eldert]

i had the cam in a engine and took some timing readings . here they are :

timing was taken at 1 mm lift with zero running clearance

intake opens 43 degrees closes 53 degrees . duration 276 degrees lobecentre 95 degrees .

exhaust opens 53 degrees closes 33 degrees . duration 266 degrees lobecentre 100 degrees .

i am very curious how the engine performs

Eldert

[Kthomas]

Eldert
What kind of frame is your mx 450 ? I ran the vintage MX up until last year. ( sometimes on a NC ducati ) I always wanted to try a cheney frame with a ducati 250 engine.
Thanks