Wanted Ducati 250 Clutch

[alno]

Hello,
I'm having the engine serviced on my 1966 Ducati 250 Narrow Case. The Clutch Basket and Hub are in very bad shape. Does any one in Motoscrubs any a good one they might want to sell?
Thank You for any help you can give me
Al

[krupp13]

Do you have pics of exactly the parts you need? I believe I have a couple lying around.

[ecurbruce]

Count the teeth, there are different ones

[Eldert]

250 ratio is 24 / 60 = 1 - 2.5

350 and 450 ratio is 27 / 57 = 1 - 2.11

Eldert

[DewCatTea-Bob]

" 250 ratio is 24 / 60 = 1 - 2.5
350 and 450 ratio is 27 / 57 = 1 - 2.11 "

____ The 1:2.111 ratio-set will work okay on a 250-motor, however it wouldn't be a good-idea to try the 1:2.50 ratio-set on a larger motor (as it would be hard on the transmission).
__ When Ducati developed the newer primary gear-set (for the 300/350), they should've just gone-ahead & used that same 1:2.111 ratio-set on all the (new/5-speed) 250-motors as well !
And the 450-motors really should've gotten an even taller / new ratio-set ! _ Of which, while Ducati-itself apparently never bothered to do, I do believe however that Eldert has worked-out a fairly good ratio for.
So Eldert, could you (once again) please show&tell us more about that (impressive!) achievement of yours ?


Hopeful-Cheers,
-Bob

[Eldert]

Hi Bob

the clutch was in this thread :

viewtopic.php?f=3&t=20&start=20

my clutch has a 1/ 1.827 ratio . Nova racing transmissions makes a clutch with a 1 / 1.875 ratio

Eldert

[DewCatTea-Bob]

" the clutch was in this thread : "

____ Thanks for that link Eldert ! _ I guess that was the best way to handle my request of re-covering that particular primary gear-set topic here, as it's somewhat off-topic here in this particular thread. _ However I-myself feel that it helps to make THIS otherwise fairly boring thread-topic, far more interesting (without getting too far off track).
And also, that link leads-back to an older thread, (started by fellow-member 'Thevin'), which also includes other topics of certain interests as well.


" my clutch has a 1/ 1.827 ratio. "

____ That particular ratio is the result of the (custom!) 29t & 53t primary-set, and seems like a pretty-good primary-ratio that's well suited for a 450 (to 500cc) motor !
How did you happen to come-up with such gears, with that particular number of teeth ?


" Nova racing transmissions makes a clutch with a 1 / 1.875 ratio "

____ I wasn't aware that anyone other than yourself had anything of the like. _ Thanks for that additional great information ! _ As it should be of interest to anyone with a 350 or 450 motor (for racing or not) ! _ As these better-suited primary-ratios relieve the transmission-gears from having to cope with as much multiplied-torque, as the stock primary-gears cause, (for trans.gears originally intended for 250-motors).


____ I've re-posted your picture of your custom-made primary-set...
It's too-bad that the other-side of the driven-gear is not viewed,
what drive/friction clutch-plates does it take ?


Dukaddy-DUKEs,
-Bob

[LaceyDucati]

I Commissioned Nova to make the 1.875 ratio for our 450 racers in the 90's. We wanted to reduce the torque through the teeth and we had also run out of gearing on the Island. It improved the situation, but it still didn’t stop the gears breaking in the Nova box's after a few years. Eldert had the same problems, which is why he had heavier duty gears made for his 450 racers. Nova have made a few batches of the 1,875 ratio gears for me over the years. I am Due to review the Nova gearbox's with them later this year and hopefully we can overcome these issues with the 450 racers.

http://www.laceyducati.com/ducati-parts ... bb19560839

Nigel

[Rocla]

Hello,

I saw this topic is about reduction, so I post again my question (here below) because it is difficult to find any book of specifications... I have almost achieved my Scrambler 350 restoration. You can have a glance here : http://strv.pagesperso-orange.fr/motode ... Ducati.htm at the bottom of the page.

But I have a problem of reduction radio : at 5000 t/mn, it seems I am around 95 km/h (59 Miles/h) and the reduction ratio seems very short, more convenient for trial than for the road... I have a 15 teeth sprocket at the gear box exit, and a 57 teeth crown on the rear wheel !

Does somebody have the same reduction ratio with his 350 (or 250) Ducati ? Can somebody tell me the exact speed at 1000 rpm in 5th speed with such ratio 15x57 or with any other ratio in order I recalculate to check if I am wrong or not ? I would like to make sure my calculation is OK before ordering a 16 teeth sprocket and a 40 teeth crown given that I have neither speedometer nor rev control !

[DewCatTea-Bob]

[quote= Rocla ...
" I saw this topic is about reduction, so I post again my question (here below) because it is difficult to find any book of specifications...

____ Firstly,, your topic-matter is not very-much related to THIS thread's topic-title, so you ought-to have rather begun a new dedicated thread of your own concerning sprocket-gearing, (instead of clutch-parts quests).
__ Anyhow,, here are a couple other more-related threads in-which you may find at-least one thread-posting of interest...
viewtopic.php?f=3&t=564&p=3574&#p3572
viewtopic.php?f=3&t=26&p=257&#p257
__ If you find something you'd like to follow-up on within either one of those threads, then please respond with your response-post placed within THAT thread (rather than this-one).



" I have a problem of reduction radio : at 5000 t/mn, it seems I am around 95 km/h (59 Miles/h) "

____ Is that while in 5th-gear ?
How did you determine that your speed was 59MPH / 95k/h with your eng.revs at 5000-RPM ?
In order to obtain 59-MPH at 5000-RPM in 5th-gear, you'd need 49/15t sprockets with a rear-wheel circumference of 83.4-inches.



" I have a 15 teeth sprocket at the gear box exit, and a 57 teeth crown on the rear wheel ! "

____ Your 57/15t-gearing -(with resulting ratio of: 3.8:1) is indeed quite low for road-riding (and-so more suitable for off-road/hill-climbing). _ So therefore, you indeed ought to at-least change the rear-sprocket, to a considerably smaller size !



" Does somebody have the same reduction ratio with his 350 (or 250) Ducati ? "

____ Be aware that any motor-model smaller than a 350, does-not have the same primary-ratio, and-thus won't have the same RPM/MPH ratios even with the exact-SAME sized front & rear sprockets !
So INSTEAD of also taking into consideration any "250" model (for comparing to your 350),, rather-instead, consider sprocket-gearing comparisons with 450-models.
__ And BTW, it's quite rather doubtful that you'd find anyone-else who happens to also have a 3.8:1 sprockets-ratio on their 350 or 450 Duke !



" Can somebody tell me the exact speed at 1000 rpm in 5th speed with such ratio 15x57 or with any other ratio in order I recalculate to check if I am wrong or not ? "

____ Most certainly YES ! ... I-myself can check that for you, as gearing-ratio figuring has been one of my FAVORITE-topics (for all OHC Duke-models) !
__ The 350 motor-tran's internally-resulting gear-ratio with 5th-gear engaged is: 2.043:1, so that would make YOUR overall-ratio (in 5th-gear, with 57/15t)= '7.76:1' ! _ Which means your rear-wheel makes 1 complete-turn for every 7&3/4ths crankshaft-rotations.
Next, assuming that your rear-wheel has an average circumference of 83-inches, that would mean that at 1000-RPM, your 350SCR would be rolling-along at about 10.1-MPH.
So-then at 5000-RPM, that ought to be about 81k/h,, (not "95").



" I would like to make sure my calculation is OK before ordering a 16 teeth sprocket and a 40 teeth crown given that I have neither speedometer nor rev control ! "

____ That better-suited combo of sprockets would yield a ratio of 2.5:1, which would result with an overall-ratio of 5.11:1 (in 5th-gear).
So-then at 1000-RPM, your rear-wheel would thus-then rotate 195.7 times per-minute, (or 11742 times per-hour),, and with an averaged-sized rear-tire, that would result with you rolling-along at about 15.4-MPH.
And at 5000-RPM, that would then become near 77-MPH,, (and as I recall a kilometer being 5/8ths of a mile), that speed ought-to convert to 124k/h.
__ Your consideration of a 40t.rear-sprocket is indeed a drastic-reduction, of which itself-alone would raise your overall-gearing by about 30%, which would thusly reduce your engine-revs from 5000-RPM to just 3500 (at the 95km/h *).
This 40/15t.gearing is the stock-gearing for a 350Mark3D and is sufficiently high enough.
If you also go-with a 16t front-sprocket as well, then your overall-gearing would be raised another 7%, (which would lower your eng.revs down-to nearly 3280-RPM, [at the 95km/h*]).
(* These RPM/speed results I've come-up with, [all resulted accordingly with YOUR posted base-line figures], must certainly be pretty-much out-of-line from that which should actually be. _ So now that I've completed my-own calculations, it turns-out that your "95 km/h" at 5000-RPM [with the 57/15t gearing] is about 15% off-from the actual-case.
In-order for BOTH of our posted-figures to be all correct, your 350's rear-wheel circumference would have to be a whopping 96-inches in circumference ! _ And the largest 18in.rear-tire* that I've ever measured, was only nearly 88-inches ! _ So I'm thinking that YOU must've figured something wrongly somehow.
(The smallest 18" tire I've ever measured, was 77-inches.)

____ In-order to properly calculate your eng.RPMs at any particular speed, or vice-versa,, ya first need to know the rolling-circumference of your rear-wheel, and your Duke's overall gear-ratio.
So do you happen to already know the circumference of your read-wheel ?



Hopeful-Cheers,
DCT-Bob