MAKING CHANGES IN A 24 HORAS

[DewCatTea-Bob]

By JPALOMO: _ " 3 Stage: Crakshaft 57.8, before 66, and piston 76, before 69. For this big change It was neccesary to reposition the boltholes
buy a strada 250 head and cilinder (74 mm) and rebore to 76 mm.
Many problems with the piston touching the head, I broke the holes and I must tu rebuilt with helicoil. "

_____ Okay J., here follows my understanding of what you went-thru with your project-motor, so far.....
___ Your original 24Horas-motor broke it's con.rod, so you replaced it's crankshaft -(66mm-stroke type) with a used 250-Strada crankshaft -(57.8mm-stroke type),, and also attempted to install the Strada's cylinder-jug -(74mm type), & cyl.head onto the 24Horas bottom-end.
Also bored that cyl.jug to accept a 76mm 350-piston.
All correct?
___ Then had to deal with the following problems.....
_ Because the bolt-pattern of the Strada-cyl.jug spreads the left & right cylinder-bolt pairs further apart than those of the 24Horas (square bolt-pattern),, you had to (do just as Eldert claimed would need to be done and) make new threaded-holes into the 24Horas crankcase, to match the wider bolt-pattern of the top-end from the Strada.
But afterwords, you ran-into the following set-backs.....
_ The newly relocated bolt-holes were too week (placed near the L & R edges of the cylinder-base/mounting-platform), and now must be repaired.
_ The 350-piston on the Strata con.rod is too tall for the Strada-cyl.jug (when mounted to the 24Horas-crankcase), so the piston now makes contact with the cyl.head.
___ I wish to know how high the outer/top edge (not crown) of the piston rises above/past the top of the cyl.sleeve!? _ As I believe that I may have a single solution for fixing both problems...
I suggest that you might make a platform-adapter/spacer-plate (the same size as the base of the Strada-cyl.jug), with 4 holes matching the smaller/square bolt-pattern of the 24Horas-crankcase, plus 4 additional threaded holes for the wider pattern of the Strada's top-end.
With such an adapter-plate, (made from whatever good metal-stock you have), you could bolt it down to the crankcase's cylinder-base/mounting-platform (using flat-head bolts), then bolt the Strada's top-end down to the adapter-plate.
_[Eldert, could you please confirm whether or not that the two sets of 4 holes would not overlap into the same spaces ?] - Otherwise, another set of completely new holes will have to be tapped somewhere else into the crankcase's cylinder-base/mounting-platform. (With matching holes in the adapter-plate).
___ I sure wish that I could personally look-over all the parts in question! _ So that I could then make better suggestions.
____ When this project, (as I now understand it to be), is completed,, you will then have an engine with 262 CCs ! - (Not as exciting as the 299cc [76x66mm] project !)
I hope we'll all see you through your project, JPALOMO !

Hopeful Cheers,
-Bob

[JPALOMO]

I will try to answer everything:
-The crankshaft I used was a totaly brand new from a 200 Elite (narrowcase) the Strada I know is wide case.
-The holes was so wek because even if the mechanic put aluminium in the oldones, that was a poor quality
-I think the problem with the piston was because the Strada’s head is 74 mm and the piston 76 then it thoes’nt much.
-Now I think the problem withe the holes is resolved, I put a tempered helicoil, do you know it?
Then the situation is to check the timing in the crankshaft, Elder says that it must be the “eleven” point , and I’m not sure wich is the situation, to control the valves gauges, and the geometric compresion.
When De 24 H started to go O.K. with out smoke a lot, not to much noise in the engine, and pushing well, I will pass to the next step, 299cc.
A question, how to control the diagram of the camshaft ? Could you describe it?
And the last do you know the original diagram of 24 horas?
Thakyou for your interest, I will give more pictures if you want, also a video if it is possible

[DewCatTea-Bob]

____ OKay JPALOMO, with your updated-info, I now understand the following details.....
_ You used a 200-crankshaft rather than a Strada-crankshaft -(as it is an incompatible wide-case type part);
_ The two sets of 4 bolt-holes (original set & newly relocated set), overlapped too greatly, and the aluminium which was added to fill-in the original set of 4 threaded-holes, did not hold-up to being used after being partially drilled & tapped/re-threaded. _ So you had to re-machine the 4 new holes so as to accept threaded-inserts -(sometimes called "tempered-helicoil"), thus making excellent threaded-holes for the 4 cylinder-bolts.
__ You think that the 76mm 350-piston is somehow too large to fit up into the Strada-head which was intended for only a 74mm piston. _ For this remaining problem, I have the following thoughts.....
Unless the Strada-head -(as well as the Strada-piston) is much different than that of all other standard 74mm-bore 250-engines, then there's no reason why a standard 350 Borgo-piston will not work with the normal 250-head! _ As I've also installed 350-pistons into 250-engines without troubles! ...
What I think is actually the cause of the piston making contact with the head, is that your cyl.jug is too short. _ (By how much, I do not exactly know in this case.) ...
Ducati made aluminium-spacers just for this type of clearance-problem! _ It's part-# is either '0600.17.025' or '0606.17.025'. _ One or the other cylinder-shim should solve that problem for you.

____ Next, I'm not exactly sure of what you actually wish to ask concerning the timing of the crankshaft to to the valves.
So could you please try again, and use different terminology to explain exactly what you are asking about?
In any case, any resulting valve-timing will not effect the calculated 'geometric-compression ratio',, however the actual valve-timing can indeed have an effect on the actual/measured-compression pressure!
__ If you wish to know what the valve-timing is of the 24Horas-camshaft, I'm sorry that I do not know those specs for sure. _ I hope that you can find-out that information directly from Mototrans (and also let me know those specs, as well !). _ (Also the valve-timing specs for the Strada-camshaft !?)
Those 24Horas-camshaft valve-timing specs may be the same as for the Mototrans 250-DeLuxe model... It's valve-timing is:
_ Intake opens - 45degrees BeforeTopDeadCenter, & closes - 85degrees AfterBottomDeadCenter ,
_ Exhaust opens - 65degrees BeforeBottomDeadCenter, & closes 45degrees AfterTopDeadCenter .

____ I hope to get more from you, (using different wording), so that I may more clearly understand exactly what you & I are actually meant to convey to one another, (mainly about your need for tech-info).

GoodCheers,
-Bob

[JPALOMO]

Hi Bob:
The situation of the engine is: 74mm bore and 66 mm stroke, many dark smoke and no too much power, I think the problem can be in: Carburator is not clean, for test I use it without air filter
Distribution timing: Doubts with the two points int the gear of the crankshaft, Elder said the correct is the eleven position, but I must to dismount to eliminate this doubt.
Ignition timing, I had no strobolamp
Real compresion ratio, because I put in the base of cilinder a plate home made, 5 mm thick.
Also I'm using a suposed 24h camshaft, after I take the figures of the diagram I will give to you but I want how to make the medition: Making the adjustement, 0,05 intake, 0,07 exaust, but I heard for some engines that to arrive to the factory figures, after the regulation, you must put a gauge 1mm thick betwen the valve tail and the rocking, do you know this?
I'm thinking to take the mesure of the camshaft and the compresion before dismount or make other modification.

[DewCatTea-Bob]

By JPALOMO:
...
" many dark smoke and no too much power, I think the problem can be in: Carburator is not clean, for test I use it without air filter "

____ I understand this to mean that the engine's exhaust produces much black-smoke, and the motor is quite notably low on power-output. ...
___ I suspect any of the following causes for that...
_ The needle-valve has come loose from it's clip;
_ The float-valve is stuck or otherwise unable to properly meter flow and keep the fuel-level properly set;
_ The idle-jet screw is set way off from normal setting.


" Distribution timing: Doubts with the two points int the gear of the crankshaft, Elder said the correct is the eleven position, but I must to dismount to eliminate this doubt. "

____ I understand this to mean that you are concerned about whether or not the timing of the crankshaft's bevel-gear is correct for the valve-timing of the camshaft which is installed in the Strada-head. _ And, that you have understood Eldert to have suggested that the tooth nearest to the 11:00-o'clock position, (perhaps instead of the standard timing-dot located at the normal 00:00/12:00-o'clock position), is the correct point on the crankshaft's bevel-gear, to set the alignment with the tower-shaft bevel-gear,, but you think that you ought to disengage from that suggested 11:00-setting, (and perhaps try another alignment position to help confirm whether or not that alignment position is actually the best/correct position. ...
__ I really don't know if Mototrans has altered the placement of any of the normal timing-marks on the bevel-gears, (or, their camshaft's slot). _ I can only suggest that you line-up all the standard timing-marks, as normal.


" Ignition timing, I had no strobolamp "

____ Set the ignition-timing statically... Spark should occur between 8 to 12 degrees BeforeTopDeadCenter.


" Real compresion ratio, because I put in the base of cilinder a plate home made, 5 mm thick."

____ I'd like to see a picture of your cylinder-base spacer/shim-plate.


" I want how to make the medition: Making the adjustement, 0,05 intake, 0,07 exaust, but I heard for some engines that to arrive to the factory figures, after the regulation, you must put a gauge 1mm thick betwen the valve tail and the rocking, do you know this? "

____ My understanding of what you mean here, is that after the valves have been set to normal working clearance, you want to perform your own reading-check of the camshaft's actual valve-timing. _ And however, that you realize that the points at which the readings (for the factory-specification figures) are to be taken/noted,, vary according to the manufacturer's preset requirements.
__ It's my understanding that the Japanese manufactures have chosen to record the reading-figures for their camshaft's valve-timing, at the point where the valve has raised 1.0mm off it's valve-seat.
I do not agree with that choice, as it's not a fair point to claim for the REAL actual valve-timing! _ (I myself believe & contend that the actual valve-timing reading-figures should be taken/recorded at whatever points when the valve permits passage of any air at all.)
__ Ducati chose some other method which varies depending of the model of camshaft. _ That makes good sense because the 'clearance-ramps' -(that part of the cam's ramp which preps the rocker-follower for the main lobe of the cam), are varied for each type of cam-lobe profile. _ Therefore you need the factory-specified figures for each camshaft model, in order to compare a reading-check of the camshaft's valve-timing.
Ducati usually provides the various clearance-figures for the required valve-clearances, for performing the reading-check of the valve-timing, for whatever camshaft model.
Sorry, I do not know what the required valve-clearances are for taking/noting the reading-check of the valve-timing for a 24Horas-camshaft model.


" I'm thinking to take the mesure of the camshaft and the compresion before dismount or make other modification. "

____ That would be a good idea, if you care to take the time & trouble to perform that troublesome task.
I suggest that instead of checking for Ducati's (unknown for this time) valve-timing & clearance figures, that you perform the valve-timing reading-check test, with the valve-clearances set at exactly 1mm, (for later comparison only).


Cheers,
-Bob

[JPALOMO]

Hello again Bob, of course thank you very much for the time you take to answer my questions, now everything is clear for me:
first, clean the carburetor, Amal 30, originally Amal 27, then spark timing, make a test, if there is still troubles go to the head, revises valve clearences, take the camshaft measures and if neccesary change the gear position.
Here a picture where you can see the base plate, home made with a drill, ahackwaw and a file, the quality is not very good but its run. Also a cilinder picture because in a moment you ask me about the numbers of fins.
Thanks again,
Juan

[DewCatTea-Bob]

" spark timing, make a test, if there is still troubles go to the head, revises valve clearences, take the camshaft measures and if neccesary change the gear position. "

____ These timing-check tests require setting-up a degree-wheel onto the left-end of the crank-shaft... That's no easy task!
It will be difficult to accurately obtain figure-readings that come within 4-degrees of the recorded factory-specified valve-timing figures.
__ Unlike the Japanese, Ducati did not choose to record their valve-timing figures at a single universal point, (such as 1mm of lift), for all their camshaft-models.
Instead, Ducati recorded their timing-figures at the moment when the base of the ACTUAL lobe of the cam, begins to lift the valve away from it's seat.
However, every model of camshaft has it's own particular clearance-ramp, (previous to the ramp of the cam-lobe), which must be taken out-of-the-picture before taking/noting any valve-timing reading-figures. _ And the factory provides the valve-clearances needed to avoid reading any part of the cam-lobe's clearance-ramp. _ Thus each camshaft model, requires a different valve-clearance setting for taking valve-timing readings.
So if you don't have the factory-specified valve-clearance figures, then you really can't get readings which should match the valve-timing specs for the model of camshaft which is installed,, (providing that you even know what the timing-specs for your camshaft are supposed to be, in the first-place!).
__ I know a good bit about how valve-timing works, so if you are without the related factory-specifications, then let me know the valve-timing reading-figures which you obtain, and then I'll let you know if those figures are usable, or should be advanced or retarded.
Just be sure to reset the valve-clearance to either 1mm or .5mm, before performing the valve-timing test & noting your readings.


" Here a picture where you can see the base plate, home made with a drill, ahackwaw and a file, the quality is not very good but its run. "

____ Your cylinder-base shim-plate looks just fine for the job!
How did you determine how thick to make it?


DUKE-Cheers,
-Bob

[Eldert]

and here a picture of some bottom bevels with timing dots and in relation to the keyway



these are real gears and no photoshopping done to them !!


Eldert

[DewCatTea-Bob]

" and here a picture of some bottom bevels with timing dots and in relation to the keyway "

____ Thanks very much for the picture of those three types of crankshaft bevel-gears, Eldert!
I have seen many examples of the first two types (left & center), but, I don't recall ever seeing one like that which you have placed on the far right-side, with TWO 'timing-dots' . _ THAT must be what JPALOMO is referring to!!
I had thought that he might be referring to a fourth type which I've come-across... It had the normal 'dot' , plus also, a vertical 'line' placed 1-tooth away (next to the dot). - (The 'line' looked to be about half as wide as the dot, & with it's length about the size of two dots). _ Have you ever seen any of that type as well?
__ Also Eldert, did you keep track of the other parts which came from the same engine as your gear with the two dots came from? _ If so, can you please tell, (or post it's picture as well), about the camshaft (top) bevel-gear's timing-mark(s) (from the same engine)... Is it as normal, or does it also have two timing-dots??
If not, do you happen to KNOW for certain, what the reason is for that strange 21t-gear to have more than one timing-dot ?

Thanks,
-Bob

[Eldert]

Hi Bob

a while back i bought 13 of these gears from a German EBay seller

my guess is these are mototrans gears but i am not sure

Eldert