Wanted Ducati 250 Clutch

[DewCatTea-Bob]

[quote= Rocla ...
" I would like to know the actual power of my white camshaft 350 Scrambler... "

____ Sorry I don't have any fully-trustworthy data on actual power-output, but the Scr.cam is significantly wilder, (although not actually considered as a 'wild' cam itself, either !), than the Monza-cam in 350-Sebring models,, and that difference along-with all the other breathing-improvements which a 350-Scrambler has, (all-together) ought-to provide 1.5 to 2.5 additional HP above that which a stock Sebring produces -(which I think is about 24-HP at the drive-sprocket). _ So it's no-doubt that your 350 produces a couple more HP @ about 500 to 1000 RPM higher (than a stock-Sebring).
So anyhow, the 'White-cam' itself offers no greatly-significant power-improvement (over the Monza/Violet-cam), although it alone certainly should provide some improvement !
__ The stock Sebring was claimed by Ducati to have a top-speed of "85+" MPH ! _ And all three Sebring-models I had, at-least met that claim ! ...
One of them, with only it's filter-box intake-hose removed, once rather easily attained 88-MPH (under ideal riding-conditions).



" (I forgot to tell you that I increased the pipe exhaust section at the top cylinder exit, But the effect is probably marginal) "

____ Right, probably rather quite "marginal"...
As it's been my experience that most-all such minor improvements (alone, all on their-own), make absolutely NO self-notable advantageous/beneficial-difference ! _ (Although, measured on a finely-calibrated D.meter, such a minor-improvement may likely register an increased 50th to a 10th of a single-HP.)
__ (Later, I may add some other examples of such).


Dukaddy-DUKEs,
-Bob

[Rocla]

Hello again,

Now, I know exactly the reduction ratio of my 350 Scrambler since I've put 2 brand new tires, and I measured the perimeter of the rear one on the ground, by the means of a spot of paint, while I was sitting on the bike and pushing it with my legs. I've measured the distance between the 2 spots on the ground : 2,02 meters, that exactly means 22,417 km/h at 1000 rpm in 5th speed and 112 km/h at 5000 rpm. But I've compared with my 250 MZ at 5000 rpm/105 km/h (thanks to my son who drove beside me on the road): I am not comfortable to push the engine up to such speed, given the piston is new and in its runing in period. But for sure, even with a brand new tire, the 17x45 teeth reduction ratio is absolutely bearable for the engine, the accelerations are pretty good.

Of course, improving the exhaust pipe has no obvious effect. Since I am 16, I am use to modify my bikes and my cars And I know what are the expected results most of the time. But in certain cases, a microscopic modification can generate huge consequences, like the exhaust in a 2 stroke engine at very low engine speed... I've built 6 or 7 exhaust silencer for my 2 stroke 250 MZ to minimize significatly the noise without any loss of power! If you like mecanic, you will see all the mods I did on this bike, with the most fruitful of them: lightening and balancing the crankshaft, clutch and primary gear (for the acceleration at every speed engine), then the programming ignition (for the torque at low engine speed), then the platinium spark plug, etc... Have a glance, you will be surprised :

http://strv.pagesperso-orange.fr/motodesign/UKETZ.htm

For my car (Golf GTI III 8 valves), it was (from the most efficient to the lower) : flying wheel lightening/balancing (for acceleration), then calculator/camshaft (for acceleration and power at medium+high speed engine), then 4/1 exhaust pipe (for medium and high speed engine), then reduction ratio of 3rd, 4rth and 5th gears (for acceleration). I am use not to modify the injection or carburetor (on my cars or bikes) because power at high engine speed is as much unexploitable as costy in gas consumption... As a result, I've lost torque below 4000 rpm but it was very profitable above, and the consumption is in certain cases lower than the genuine one

[Nick]

Well, as long as we're talking Sebrings I might as well add my 2 cents. My N/C Sebring accelerates very hard and runs very strong (for a fifty-year-old single, of course). I got a big power boost by switching to a 28mm Mikuni carb and using a longer intake manifold. I also upgraded to 12V, but didn't notice much power improvement with that mod. In any case, the bike gets off the line really well, is just purring at freeway speeds and 70~80 seems well within its capabilities. At the risk of starting a flame war, I really believe the Sebring is the best N/C Single for daily riding. The 250's are nice, but they lack punch compared to the Sebring. I commute to work regularly on mine and it's one of my favorite all-time motorcycles.

[LaceyDucati]

I agree the Sebring is the most underrated Ducati Single!

Nigel

[Jordan]

... Have a glance, you will be surprised :
http://strv.pagesperso-orange.fr/motodesign/UKETZ.htm

That was fun.
I liked my green ETZ250, but had to sell it - my wife said it was too ugly to bear!
She likes my Ducatis though.

Jordan

[Nick]

Yes, it's very ironic isn't it? The 250's and 200's get all the attention because they look so cool, and the Sebring is ignored because it looks so ugly (beauty is in the eyes of the beholder, etc.). But the Sebring is really the better machine in many ways. Even those dorky stock bars are very comfortable. I've put a lot of miles on a Monza 160, Diana MkIII and Sebring, so I have a fair amount of experience with the N/C bikes. The only caveat I would add is that larger people would probably be more comfortable on the larger w/c models.

[DewCatTea-Bob]

____ It's fairly-disconcerting that 'threads' only have vertically-ordered post-placement, because spawned off-topic posts really ought-to have the option to veer-off SIDEWAYS (towards the right) directly-from whichever post that had led-to the sidetracked post-topic. _ As all too often, threads divert-away and become more concerned with offshoot-topics which accumulate more off-topic postings than the number of posts concerning the intended-topic of the original thread-title ! _ So thus-then a thread-reader has-to wade-through a number of posts that aren't even touching-on the subject they were led-to believe they'd get to read about (according-to the 'thread-title'). _ THIS-thread has become a prime-example of such disconcerting-order ! _ With merely-just the vertically-ordered 'tree-trunk' to contain ALL the spurred side-shoots, without any 'branches' to spread them out with more organized-order.
__ Anyhow,, since we have-to put-up with such mixed-up post-topic disorder, then we all really ought-to help such disorganization to-be more easily dealt-with, by PAYING-ATTENTION to our 'Post-Titles',, as that's pretty-much the only-way we have to allow readers to-be pre-informed about whatever the main topic-mater (contained in our posts) happens to cover. _ Cuz if ya don't 'title' YOUR-post, then your post-title will default to the original topic-title of the 'thread' itself ! _ Which in this-case, is: "Wanted Ducati 250 Clutch" .
(If ya had to use a Honda-tank on your Duke, would ya then also forget to notice the Honda-name left on it ?)

[quote= Nick ...
" Well, as long as we're talking Sebrings I might as well add my 2 cents. "

____ That's fine, (even-though your post-title still indicates "250"), at-least your opening-sentence is fairly-informative.



" I got a big power boost by switching to a 28mm Mikuni carb and using a longer intake manifold. "

____ Of-course the original 24mm-carb is TOO-small for a 350-engine ! ... A 27mm size would've been a good choice for the Sebring,, but why did it end-up with the over-smallish 24mm size in the first-place ? ... I have a couple of answers...
__ Apparently Dr.T was okay-with increasing his original 62x57.8mm/175 n-c.design's capacity out-to 203cc, and then later (with some concern) out-to the 250,, BUT he was much against any further increased-capacity without also making his original-type n-c.cases more robust.
Yet the American-market/(Berliner) was pleading for a (cheap)- 300-motor (to compete with Honda's 300cc-Dream), so the 76x66mm/300-GT was expected to fill-the-bill,, and as a 'GT' model, gas-milage/tank-range was a fair concern, so-thus it was intended to be matched-up with the same miserly 24mm-Del.carb as employed on the 250-GT.
But by the time the 300-motor was delayed for near 2-years, (supposedly mainly due-to protest by Dr.T),, Berliner wanted to stay abreast with the Jap.bike market-trend (towards larger engine-sizes), and jumped-over/ahead to the n-c.350 (for the 1965 model-year). _ But because the motor-cases were still-not sufficiently beefed-up for full-on 350-power (in the eyes of Dr.T), the Sebring's tuning was kept as mild as possible (with pre-existing parts, such-as the mild 250Monza-cam). _ And-so also the small 24mm carb.size was therefore retained for the n-c.350 !



" I also upgraded to 12V, but didn't notice much power improvement with that mod. "

____ It shouldn't be expected that the ign.spark of a 12v.system should be any different at power-production than that of a 6v.system.



" the bike gets off the line really well, "

____ Indeed-so, especially with 45/14t or 50/16t sprocket-gearing (which let's 5th-gear wind-out at the end of a 1/4-mile track) !
__ And-also the n-c.350 is notably better at that, than the w-c.350.
And I believe the main-reason for that, is due-to other than the difference in motor-case weight, (which I'll address in my next-post).



" I really believe the Sebring is the best N/C Single for daily riding. "

____ Vibration aside, I certainly agree !


Duke-Cheers,
-Bob

[graeme]

How about posting some pictures ?

[DewCatTea-Bob]

[quote= LaceyDucati ...
" I agree the Sebring is the most underrated Ducati Single! "

____ I wonder in exactly-what respect you most mean that, Nigel. _ Certainly-not in respect to it's 'looks', so I most assume that you rather likely must mean in respect to performance. _ As it seems that the n-c.Sebring gives-up nothing* to stock w-c.350-models equipped with wild Green&White-cams & larger carbs, etc., (* at-least in standing-start races). _ And I think there's a major-factor responsible for that conundrum. ...
(Some of you may already know where I'm about-to lay-blame for the n-c.350's power-advantage, as I've already posted on this in the past.)
__ Engine-torque is resulted from two factors... combustion-pressure & LEVERAGE !
Leverage-value depends-on the crankshaft's 'stroke' and also on the 'angle' at-which the con.rod has-to push against the crankshaft-pin. ... It would be absolute-optimum for the con.rod to be pushing against the c.pin when it's at a 90-degree/right-angle whilst the cylinder's chamber-combustion is at it's maximum-pressure, also,, in-order to provide maximized-torque ! _ But such preferred exact-coincidence is-not really possible to fully achieve, so the closer that those two factors can physically-occur to each-other (in time), the better then for obtaining MAX.torque,, (unfortunately at the expense of piston-skirt to cylinder-wall wear&tear) !
And the shorter-length of the n-c.connecting-rod allows for it's better-leverage closer-to the time when the cyl.combustion-pressure is at PEAK-pressure, thus providing the max.torque-advantage over the w-c.350 !
Ya may-not think that the mere 10mm-difference could account for so-much torque-advantage, but there's nothing-much of anything-else to blame, (and after-all, it does make good mechanical-sense !).
__ If ya ever heard-of bored-out* n-c.350s matching 450s for acceleration (and even higher top-speed), the 15mm rod-length difference is likely (at-least partially !) the reason for THAT conundrum.
(* 'bored-OUT' 350s have near 370cc, [using a std.BSA.441-piston],, and re-sleeved 350-cyl.jugs have over 385cc, [with a bevel-750 4th-os.piston].)


Dukaddy-DUKEs,
-Bob

[Nick]

Here's one, some better ones will follow in a couple of days.



The Chinese/Japanese characters on the tank are from an old proverb: Dragon's Head, Snake's Tail (A good beginning and bad end....)

Bob, thanks for the background info on the 350. Strange that Dr. T. should have been worried about the cases--never heard of any breaking. Other keys to the Sebring's performance are the light weight, narrow tires and narrow pitch chain (low rolling resistance).