Info sought on alleged prototype 250 with electric start

[Jon Pegler]

I'll give it a try.
It might not be quite as straight forward as you suggest as the small sprocket is not fixed to the splines of the starter motor.
Both the crankshaft and the starter run in roller bearings in the outer cover.
The starter chain may try and fly off without the cover in place.
The chain tensioner is only sprung loaded. (Although the chain has been replaced with a new one since the photo was taken )
The sprocket on the crankshaft would probably stay in place due to the crank nut stopping it.
This nut can be seen in my photo and holds the sprag clutch housing, two needle roller bearings and some spacers outboard of the primary drive gear.
Next time I have the cover off I'll try and rig up a temporary stop for the top sprocket so that I can hold a tacho to the crank.

Jon

[Ducati Dude]

Here is a pic I found - not sure this is what you are looking for:

http://www.philaphoto.com/imageLibrary/ ... 1211&pos=1

Tony

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Grazie Tony
Yes, this is the picture.

Do you know if Ducati or Mototrans made it ?

Ciao

DD

[PhilA]

My assumption is as follows:

Ducati designed and built this motor circa 1970 (date supplied by Ian Falloon for that engine number) but it went no further. I think it is a Ducati built motor, rather than a Mototrans one because of the date, the DM - not MD prefix to the engine number (although some Mototrans motors did indeed use DM) and it has 'normal' Ducati barrel finning not the 'square' Mototrans style.

Mototrans decided to fit an electric start to their 350 for 1976 and designed the rather ungainly looking solution as per:

http://www.philaphoto.com/imageLibrary/ ... 970&pos=11

Someone at Ducati saw it and said "Hey we designed a better version years ago, here are the drawings". Mototrans then used that design from 1980.

I don't know if we will ever get a definitive answer 40 odd years later!

[Jon Pegler]

Phil could well be right regarding who originally designed the chain drive starter.
The earlier starter arrangement used by Mototrans for the singles was probably designed by them after their experience of building the parallel twin Ducatis.
It uses the same starter motor as the parallel twins with a gear drive on the starter itself.
It also utilises the standard wide case bottom end.
I get the impression that they took the bottom end of a single and a parallel twin starter and worked out a way of grafting the two together.
As I said in a previous post, the chain drive starter required a different crankshaft fitted to the bottom end of the motor.
Phil is also correct in saying that later Mototrans engine numbers are usually prefixed DM rather than MD.
They are numbered in a different series to the Italian built motors, though.
The squarer cylinder barrel (jug)fitted to some of the later Mototrans machines is a bit harder to pin down.
I've seen Forzas and Ventos with both rounded cylinders and square cylinders.
I've also seen narrowcase Mototrans singles fitted with the square barrel.
What the reason for all these differences was may never be known.

Jon

[PhilA]

"I've also seen narrowcase Mototrans singles fitted with the square barrel."

Ian has one of those, a 175. It was a bit too messy to take pics of this visit.

[DewCatTea-Bob]

" I've also seen narrowcase Mototrans singles fitted with the square barrel."

____ I like the square-styled cyl.jug only because I've always preferred unique
-things and I've never seen that jug-style on any Duke-single here in the USA, and also because it better logically matches the related style of the squared-finned cyl.head.
But, I really don't care for the added weight, nor the way it takes-away from the (long established) rather distinctly unique & strangely-weird overall-shape of the cylinder & head combo (of the original square-head & round-cyl.jug combined-appearance),, as I'm sure most all of us have been somewhat strangely bewitched by).


" Ian has one of those, a 175. "

____ This I find hard to believe without seeing such for myself, cuz the '175' was the only model I've ever known of to have it's cyl.head finning-style match that of the std.round-style cyl.jug ! _ (How weird that would look with a round-style cyl.head atop a square-styled cyl.jug !?)
__ I believe the 175's original round-head finning was later squared-out due to head-cooling concerns (probably when the compression-ratio was to become raised-up).


Dukaddy-DUKEs,
-Bob

[PhilA]

" Ian has one of those, a 175. "

____ This I find hard to believe without seeing such for myself, cuz the '175' was the only model I've ever known of to have it's cyl.head finning-style match that of the std.round-style cyl.jug ! _ (How weird that would look with a round-style cyl.head atop a square-styled cyl.jug !?)
__ I believe the 175's original round-head finning was later squared-out due to head-cooling concerns (probably when the compression-ratio was to become raised-up).

A detail from the "Wall of Engines"!

[DewCatTea-Bob]

" A detail from the "Wall of Engines"! "

____ WOW, thanks very-much for the pic !! _ Quite interesting !
__ On the left-side, the motor is obviously indeed an original round-head version 175-model,, however concerning the motor on the right-side, I doubt that it's a mere 175... as it looks to me to be a 200, and one of the later-version type 200s as well.
I'd like to know Eldert's opinion on just what these two Duke-motors appear to actually be, to him !
____ I've now altered the pic for (hopeful) improved viewing.

Dukaddy-DUKEs,
-Bob

[PhilA]

however concerning the motor on the right-side, I doubt that it's a mere 175...

From memory it has a 175 engine number...

[DewCatTea-Bob]

" From memory it has a 175 engine number... "

____ Very well could possibly be, as I know that after the 200-motors came-to-be, the 175s then became sleeved-down 200s. _ So if BOTH pictured motors are indeed 175s, then I'd bet that the one on the right-side has an extra-thick 175-cyl.sleeve in it's cyl.jug/barrow.
__ While I would've trusted Eldert's opinion, it would be nice if at least one of our other Duke-knowledgeable members in Spain could give us some more definite info concerning the motor with the square-type top-end !


Hopeful-Cheers,
-Bob