MAKING CHANGES IN A 24 HORAS

[JPALOMO]

Now I'm foing a transformation in a 250 24 horas, I have change the piston, original is 69 mm diameter, for an other one with 74 mm diameter, the displacement is 66 mm then I have a little bit more cc, the head is from a 250 strada and the problem is that the distribution shaft is to short ¿Do yo know if it exist a shaft for this combination?

[Eldert]

Did you look at a 350 bevelshaft ? they are longer about 12 mm . a 450 bevelshaft is even longer

Eldert

[JPALOMO]

Thank you Elder you are a Machine, I have a shaft from the 350 and is so longer.Now I'am a little busy nex time I will ask how to send my pictures and videos of the restoration

[DewCatTea-Bob]

By: "JPALOMO" ...
" Now I'm foing a transformation in a 250 24 horas,
and the problem is that the distribution shaft is to short ¿Do yo know if it exist a shaft for this combination? "


______ Where are you JPALOMO, Spain ?
__ I believe that what you're referring to by : "distribution shaft" , is, the OverHeadCam's upper drive-shaft, which (as far as I know), has always been called the 'tower-shaft'.

_____ I have always wanted to get my hands on one of those long-stroke 250s!!
Mainly because I wanted to try building one of the 300cc singles which I once heard that Ducati had once intended to make, back around 1964.
It's Bore & Stroke was to be 76 x 66mm, but Berliner insisted that Ducati go-ahead & try to make a 350cc for them instead. _ So the 300 got stroked-out (from 66 to 75mm) to make the (340cc) 350-Sebring for 1965. _ (Did anyone else besides myself ever wonder why Ducati didn't design their 350 to have a 77mm-bore, so as to make their 350 a full 349cc!?)
___ I believe that it was MotoTrans who instead decided to sleeve-down the 300 design to 69mm, in order to make a 250 with stronger low-end torque.
_ [ If anyone else has ever heard tale of Ducati's intended '300' engine, please tell us whatever you know of it! ...
I first heard talk of a '300', (a 5-speed narrow-case motor), back near the time when the wide-case models were to be imported into the U.S.... That in 1963, there was some expectation that 300cc Scrambler & GT models were to be produced for the following '64 model-year. _ Wow, if only they had gone through with that! Darn Berliner, I guess. ]

____ I am super-interested in your 250-combo project, JPALOMO !! _ I really wish to know all about it!
If I had ever got a chance to work on that long-stroke 250-engine which you have, then I'd now be able to tell you all you need to know! _ But since that's sadly not the case, I'll be only of little help to you.
__ Can you tell me the length of the original bevel-gear/tower-shaft (tip to tip)? _ In other words, how tall is the shaft while standing up-side-down, on it's bevel-gear head?
There are (at least) 5 different lengths of the upper bevel/tower-shafts! _ And currently, I do not know if your long-stroke 250-engine has it's very own unique length for the shaft.
__ There are two different such cam-driveshaft lengths for the 350-models! ... The shorter tower-shaft for the NarrowCase model (which is also the same shaft for all the standard WideCase-250s), and also, the longer tower-shaft for the WideCase 350 models.
So which 350 tower-shaft was it that you have already tried (and found to be too long)? _ Also, how much was it too long by?
Your '24 Horas' is a NarrowCase motor-type, correct JPALOMO ? _ If so, I'd guess that the designers of that unusual 250-motor, would have attempted to employ the WideCase-250's tower-shaft. _ I sure would like to know exactly! (As I'm always very hungry for such info which I don't already know of !!)
__ I do have some experience with grinding-down the lower & upper bevel-shaft tips a few mm, (so as to accommodate an old project on mine), so I might be of some help if that's needed to be tried for your project.
However, I'm wondering why you can't just move the original tower-shaft (and it's matched camshaft bevel-gear) over to the 74mm/std.250-head? _ I can instruct you on that technical-job, if that will do the job for you, (as I'd otherwise expect).

____ I can't wait to learn what all you had to do to put the 74mm-piston into the 66mm-stroke engine!
Did you have to put a larger cyl.sleeve into the stock cylinder, or just bore it out?
Did the motor-cases also need to be bored, (to accept a larger cyl.sleeve) ?
If so, I'd like to know what all else stands in the way of moving the entire top-end (cylinder, piston & head) from your Strada, or a 350, over to your 24-Horas project-motor !?
__ How many fins does your 24-Horas-cylinder have, 8 fins (like other 250-motors)? _ How much taller is it than your Strada-cylinder?
I'd also like to see pictures of both motor-cases, where the cyl.jug mounts. _ As well as the Strada & 24Horas pistons, side by side with rist-pin holes on one pin.
__ Do you have many WideCase-250 models where you live?

____ Anyhow JPALOMO, when your very neat & impressive project is completed, you will then have increased your 247cc '24-Horas' up to 284cc !

DukeCheers,
DewCatTea-Bob

[blabber]

OMG-he's human--and i was starting to believe in reincarnation

[Eldert]

the conversion from a 24 Horas to a 74 mm bore is not that easy . the 24 Horas uses 175 / 200 type narrow crankcases
( with a 5 speed cluster ) and the same headbolt spacing . so you have to weld up the boltholes for the headbolts
enlarge the hole in the cases where the barrel goes into to 80 mm and drill and tap new cilinderbolts holes for the
250 / 350 barrels and heads spacing .

Eldert

[DewCatTea-Bob]

By Eldert ...
" the conversion from a 24 Horas to a 74 mm bore is not that easy . the 24 Horas uses 175 / 200 type narrow crankcases ( with a 5 speed cluster ) and the same headbolt spacing . so you have to weld up the boltholes for the headbolts enlarge the hole in the cases where the barrel goes into to 80 mm and drill and tap new cilinderbolts holes for the 250 / 350 barrels and heads spacing . "

____ Wow Eldert, if all that were true, I can't see why anyone would even bother to conceive such a non bolt-together type project!
I had heard that the MotoTrans motors (in Spain) were always about 5-years behind what the Italians produced, and it does make some sense that the long-stroke 250 would be just a bored & stroked 200.
But there must be something wrong with your theory as to what JPALOMO must be doing, because for one thing, the (common) 5-speed trans won't fit in the old 200 cases!
Are you sure that the 24Horas has that same SQUARE head-bolt pattern as the 175/200 models?
Cuz if so, then maybe he has moved the 66mm-crank to the 250-Strada motor (providing that it's also a narrow-case motor).
__ I sure hope that we can get JPALOMO to give us a good/complete explanation of what all he's planing for his project ! _ (As this is the type of DUKE-projects which I've always liked to do!)

-Bob

[Eldert]

Bob
the spanish where no way behind in developmend . they made a 125 4 cilinder and had a 4 valve head for the 250
the Ducati 125 scrambler had a spanish 125 engine fitted with a 5 speed gearbox

Eldert

[DewCatTea-Bob]

" the spanish where no way behind in developmend . "


____ Oh-oh Eldert, I sure did not mean at all to imply that the 'Spanish' were any at all behind the Italians in any kind of general development ! _ That would be something which I have absolutely no first-hand knowledge of, (seemingly unlike yourself).
I had now better clarify just exactly what I had actually intended to indicate... I actually only meant that I had read somewhere that MotoTrans would continue-on to produce (obsolete) Ducati-motor-designs for about 5-years after the Italian-manufactures (of DUCATIs) had stopped production of those same old Ducati-motor-designs,, and also, that whatever new motor-designs that Ducati (in Italy) would produce, MotoTrans would not duplicate until about 5-years later.
Now that's all which I had meant to convey (in those regards)! _ Although I do understand how what I had written before could possibly be taken in the way which it seems that you had, Eldert.
__ So now that I have clarified exactly what I had actually meant, can you (or anyone else) confirm whether or not it's fairly accurate?
____ By the way Eldert, as most always, I have found your bits of information to be of interest!

-Bob

[Eldert]

Here a picture of a 69 bore 250 head. you can see the 175 / 200 stud pattern
a normal 175 / 200 cc headcasting is flat and smooth on top . this one is a little arched and has finning

the 66 mm stroke crank is just as wide as a 175 / 200 item . so both flywheels the same
a 57.8 mm stroke narrowcase crank has the lefthand flywheel wider

Eldert